827 lines
43 KiB
Plaintext
827 lines
43 KiB
Plaintext
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DHCP FAQ
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Author
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John Wobus, jmwobus@syr.edu (corrections welcome)
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Date
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3/28/96
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This file
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http://web.syr.edu/~jmwobus/comfaqs/dhcp.faq.html
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Questions
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1. General
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1. What is DHCP?
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2. What is DHCP's purpose?
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3. Who Created It? How Was It Created?
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4. How is it different that BOOTP or RARP?
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5. Why shouldn't clients assign IP numbers without the use of a
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server?
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6. Can DHCP support statically defined addresses?
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7. Can a BOOTP client boot from a DHCP server?
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8. Can a DHCP client boot from a BOOTP server?
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9. Is a DHCP server "supposed to" be able to support a BOOTP
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client?
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10. Is a DHCP client "supposed to" be able to use a BOOTP server?
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11. Can a DHCP client update its DNS entry through DHCP?
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12. Can a DHCP server back up another DHCP server?
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13. When will the server to server protocol be defined?
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14. Is there a DHCP mailing list?
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15. In a subnetted environment, how does the DHCP server discover
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what subnet a request has come from?
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16. Where is DHCP defined?
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17. What other sources of information are available?
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18. Can DHCP support remote access?
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19. Can a client have a home address and still float?
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20. How can I relay DHCP if my router does not support it?
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21. How do I migrate my site from BOOTP to DHCP?
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22. Can you limit which MAC addresses are allowed to roam?
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23. What are the Gotcha's?
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2. Info on Implementations
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1. What features or restrictions can a DHCP server have?
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2. What freeware DHCP servers are available?
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3. What commercial DHCP servers are available?
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4. Which vendors of client software currently support DHCP?
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5. What are the DHCP plans of major client-software vendors?
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6. What Routers forward DHCP requests?
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7. What Routers include DHCP servers?
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8. What Servers forward DHCP requests?
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9. Which implementations support or require the broadcast flag?
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10. How can I run Windows 95 without a DHCP server?
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11. Do any servers limit the MAC addresses that may roam?
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12. What are the Gotcha's specific to various implementations?
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Answers
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1. General
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1. What is DHCP?
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DHCP stands for "Dynamic Host Configuration Protocol".
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2. What is DHCP's purpose?
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DHCP's purpose is to enable individual computers on an IP
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network to extract their configurations from a server (the
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'DHCP server') or servers, in particular, servers that have
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no exact information about the individual computers until
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they request the information. The overall purpose of this is
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to reduce the work necessary to administer a large IP
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network.
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3. Who Created It? How Was It Created?
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DHCP was created by the Dynamic Host Configuration Working
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Group of the Internet Engineering Task Force (IETF; a
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volunteer organization which defines protocols for use on the
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Internet). As such, it's definition is recorded in an
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Internet RFC and the Internet Activities Board (IAB) is
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asserting its status as to Internet Standardization. As of
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this writing (March 1996), DHCP is an Internet Proposed
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Standard Protocl and is Elective. BOOTP is an Internet Draft
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Standard Protocol and is Recommended. For more information on
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Internet standardization, see RFC1920 (March 1996).
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4. How is it different that BOOTP or RARP?
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DHCP is based on BOOTP and maintains some backward
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compatibility. The main difference is that BOOTP was designed
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for manual pre-configuration of the host information in a
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server database, while DHCP allows for dynamic allocation of
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network addresses and configurations to newly attached hosts.
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Additionally, DHCP allows for recovery and reallocation of
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network addresses through a leasing mechanism.
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RARP is a protocol used by Sun and other vendors that allows
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a computer to find out its own IP number, which is one of the
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protocol parameters typically passed to the client system by
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DHCP or BOOTP. RARP doesn't support other parameters and
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using it, a server can only serve a single LAN. DHCP and
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BOOTP are designed so they can be routed.
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5. Why shouldn't clients assign IP numbers without the use of a
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server?
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It is theoretically possible for client-machines to find
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addresses to use by picking an address out of the blue and
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broadcasting a request of all the other client machines to
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see if they are using them. Appletalk is designed around this
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idea, and Apple's MacTCP can be configured to do this for IP.
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However, this method of IP address assignment has
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disadvantages.
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1. A computer that needs a permanently-assigned IP number
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might be turned off and lose its number to a machine
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coming up. This has problems both for finding services
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and for security.
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2. A network might be temporarily divided into two
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non-communicating networks while a network component is
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not functioning. During this time, two different
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client-machines might end up claiming the same IP
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number. When the network comes back, they start
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malfunctioning.
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3. If such dynamic assignment is to be confined to ranges
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of IP addresses, then the ranges are configured in each
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desktop machine rather than being centrally
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administered. This can lead both to hidden configuration
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errors and to difficulty in changing the range. Another
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problem with the use of such ranges is keeping it easy
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to move a computer from one subnet to another.
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6. Can DHCP support statically defined addresses?
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Yes. At least there is nothing in the protocol to preclude
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this and one expects it to be a feature of any DHCP server.
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This is really a server matter and the client should work
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either way. The RFC refers to this as manual allocation.
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7. Can a BOOTP client boot from a DHCP server?
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Only if the DHCP server is specifically written to also
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handle BOOTP queries.
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8. Can a DHCP client boot from a BOOTP server?
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Only if the DHCP client were specifically written to make use
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of the answer from a BOOTP server. It would presumeably treat
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a BOOTP reply as an unending lease on the IP address.
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In particular, the TCP/IP stack included with Windows 95 Does
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not have this capability.
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9. Is a DHCP server "supposed to" be able to support a BOOTP
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client?
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The RFC on such interoperability (1541) is clear: "In
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summary, a DHCP server: ... MAY support BOOTP clients,"
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(section 2). The word "MAY" indicates such support, however
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useful, is left as an option.
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10. Is a DHCP client "supposed to" be able to use a BOOTP server?
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The RFC on such interoperability (1541) is clear: "A DHCP
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client MAY use a reply from a BOOTP server if the
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configuration returned from the BOOTP server is acceptable to
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the DHCP client." (section 3). The word "MAY" indicates such
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support, however useful, is left as an option.
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11. Can a DHCP client update its DNS entry through DHCP?
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No. There has been some discussion about adding this ability
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to DHCP.
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(Note: as far as I can tell, the DNS needs no protocol update
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since the server already tells the clients how long they can
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use the information they receive; what is really needed is a
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DNS server that can make fuller use of this feature and that
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cooperates with a DHCP server, perhaps through the use of
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some new "DHCP-server-to-DNS-server" protocol).
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12. Can a DHCP server back up another DHCP server?
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This is the purpose of the "server to server protocol" (see
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next question). I know of no other way that you can keep a
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"hot" spare server in synch with your production server.
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However, it is possible that some server vendors have
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addressed this issue with their own features.
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13. When will the server to server protocol be defined?
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The DHC WG of the IETF is actively investigating the issues
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in inter-server communication. The protocol should be defined
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"soon".
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14. Is there a DHCP mailing list?
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There are several:
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List Purpose
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---- -------
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dhcp-v4@bucknell.edu General discussion: a good list for
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server administrators.
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dhcp-bake@bucknell.edu DHCP bakeoffs
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dhcp-impl@bucknell.edu Implementations
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dhcp-serve@bucknell.edu Server to server protocol
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dhcp-dns@bucknell.edu DNS-DHCP issues
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dhcp-v6@bucknell.edu DHCP for IPv6
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The lists are run by listserv@bucknell.edu which can be used to
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subscribe and sign off. Archives for the dhcp-v4 list (which
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used to be called the host-conf list) are stored at
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ftp://ftp.bucknell.edu/pub/dhcp/.
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15. In a subnetted environment, how does the DHCP server discover
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what subnet a request has come from?
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DHCP client messages are sent to off-net servers by DHCP
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relay agents, which are often a part of an IP router. The
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DHCP relay agent records the subnet from which the message
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was received in the DHCP message header for use by the DHCP
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server.
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Note: a DHCP relay agent is the same thing as a BOOTP relay
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agent, and the latter phrase is more commonly used.
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16. Where is DHCP defined?
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In Internet RFCs.
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RFC1541
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R. Droms, "Dynamic Host Configuration Protocol",
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10/27/1993.
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RFC1534
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R. Droms, "Interoperation Between DHCP and BOOTP",
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10/08/1993.
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RFC1533
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S. Alexander, R. Droms, "DHCP Options and BOOTP
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Vendor Extensions", 10/08/1993.
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A web site for RFCs is:
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http://ds.internic.net/ds/dspg1intdoc.html
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17. What other sources of information are available?
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See the dhcp-v4 mailing list mentioned above as well as its
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archives.
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DHCP - Dynamic Host Configuration Protocol
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http://www.bucknell.edu/~droms/dhcp/
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Problems and Solutions of DHCP: Experiences with DHCP
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implementation and Operation
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A. Tominaga, O. Nakamura, F. Teraoka, J. Murai.
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http://info.isoc.org/HMP/PAPER/127/html/paper.htm
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l
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DHCP Resources
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Alan Dobkin.
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http://NWS.CC.Emory.Edu/WebStaff/Alan/Net-Man/Com
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puting/DHCP/
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Internet Drafts
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Internet drafts are works in progress intended to
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update the current RFCs or specify additional
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functionality, and sometimes there is one or more
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draft related to DHCP. All Internet Drafts are
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available from various sites: the US East Cost site
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is ftp://ds.internic.net/internet-drafts/; a web
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site is http://ds.internic.net/ds/dsintdrafts.html.
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The DHCP-related drafts currently have filenames of
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the form "draft-ietf-dhc-SOMETHING". These
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DHCP-related drafts are also stored at
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ftp://ftp.bucknell.edu/pub/dhcp/, and are
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available through
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http://www.bucknell.edu/~droms/dhcp/. I cannot be
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more specific about the documents because they are
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by their nature temporary.
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18. Can DHCP support remote access?
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PPP has its own non-DHCP way in which communications servers
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can hand clients an IP address called IPCP (IP Control
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Protocol) but doesn't have the same flexibility as DHCP or
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BOOTP in handing out other parameters. Such a communications
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server may support the use of DHCP to acquire the IP
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addresses it gives out. This is sometimes called doing DHCP
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by proxy for the client. I know that Windows NT's remote
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access support does this.
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A feature of DHCP under development (DHCPinform) is a method
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by which a DHCP server can supply parameters to a client that
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already has an IP number. With this, a PPP client could get
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its IP number using IPCP, then get the rest of its parameters
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using this feature of DHCP.
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SLIP has no standard way in which a server can hand a client
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an IP address, but many communications servers support
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non-standard ways of doing this that can be utilized by
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scripts, etc. Thus, like communications servers supporting
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PPP, such communications servers could also support the use
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of DHCP to acquire the IP addressees to give out.
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I am not currently aware of any way in which DHCP can support
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client-computers served solely by PPP or SLIP. Such a
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computer doesn't have the IEEE-style MAC address that DHCP
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requires to act as its key to determining which
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client-computer is which within the same subnet.
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Communications servers that acquire IP numbers for their
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clients via DHCP run into the same roadblock in that they
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have just one MAC address, but need to acquire more than one
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IP address. One way such a communications server can get
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around this problem is through the use of a set of unique
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pseudo-MAC addresses for the purposes of its communications
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with the DHCP server. Another way (used by Shiva) is to use a
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different "client ID type" for your hardware address. Client
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ID type 1 means you're using MAC addresses. However, client
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ID type 0 means an ASCII string.
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19. Can a client have a home address and still float?
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There is nothing in the protocol to keep a client that
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already has a leased or permanent IP number from getting
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a(nother) lease on a temporary basis on another subnet (i.e.,
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for that laptop which is almost always in one office, but
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occiasionally is plugged in in a conference room or class
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room). Thus it is left to the server implementation to
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support such a feature. I've heard that Microsoft's NT-based
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server can do it.
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20. How can I relay DHCP if my router does not support it?
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A server on a net(subnet) can relay DHCP or BOOTP for that
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net and Windows NT is an example of a server with that
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capability.
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21. How do I migrate my site from BOOTP to DHCP?
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I don't have an answer for this, but will offer a little
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discussion. The answer depends a lot on what BOOTP server you
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are using and how you are maintaining it. If you depend
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heavily on BOOTP server software to support your existing
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clients, then the demand to support clients that support DHCP
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but not BOOTP presents you with problems. In general, you are
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faced with the choice:
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1. Find a server that is administered like your BOOTP
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server only that also serves DHCP. For example, one
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popular BOOTP server, the CMU server, has been patched
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so that it will answer DHCP queries.
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2. Run both a DHCP and a BOOTP server. It would be good if
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I could find out the gotcha's of such a setup.
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3. Adapt your site's administration to one of the available
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DHCP/BOOTP servers.
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4. Handle the non-BOOTP clients specially, e.g. turn off
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DHCP and configure them statically: not a good solution,
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but certainly one that can be done to handle the first
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few non-BOOTP clients at your site.
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22. Can you limit which MAC addresses are allowed to roam?
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Sites may choose to require central pre-configuration for all
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computers that will be able to acquire a dynamic address. A
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DHCP server could be designed to implement such a
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requirement, presumeably as an option to the server
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administerator. See section below on servers that implement
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this.
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23. What are the Gotcha's?
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o A malicious user could make trouble by putting up an
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unofficial DHCP server.
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# The immediate problem would be a server passing out
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numbers already belonging to some computer yielding
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the potential for two or more "innocent bystander"
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nodes ending up with the same IP number. Net result
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is problems using the nodes, possibly intermittent
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of one or the other is sometimes turned off.
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# A lot of problems are possible if a renegade server
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manages to get a client to accept its lease
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offering, and feeds the client its own version of
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other booting parameters. One scenario is a client
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that loads its OS over the network via tftp being
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directed to a different file (possibly on a
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different server), thus allowing the perpetrator to
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take over the client. Given that boot parameters
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are often made to control many different things
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about the computers' operation and communication,
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many other scenarios are just as serious.
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Note that BOOTP has the same vulnerabilities.
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o The "broadcast flag": DHCP includes a way in which
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client implementations unable to receive a packet with a
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specific IP address can ask the server or relay agent to
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use the broadcast IP address in the replies (a "flag"
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set by the client in the requests). The definition of
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DHCP states that implementations "should" honor this
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flag, but it doesn't say they "must". Some Microsoft
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TCP/IP implementations used this flag, which meant in
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practical terms, relay agents and servers had to
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implement it. A number of BOOTP-relay-agent
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implementations (e.g. in routers) handled DHCP just fine
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except for the need for this feature, thus they
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announced new versions stated to handle DHCP.
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o Some of the virtual LAN schemes, i.e., those that use
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the packet's IP number to decide which "virtual LAN" a
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client-computer is on for the purposes of TCP/IP, don't
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work when using DHCP to dynamically assign addresses.
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DHCP servers and relay agents use their knowledge of
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what LAN the client-station is on to select the subnet
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number for the client-station's new IP address whereas
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such switches use the subnet number sent by the
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client-station to decide which (virtual) LAN to put the
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station on.
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o Routers are sometimes configured so that one LAN on one
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port has multiple network (or subnet) numbers. When the
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router is relaying requests from such a LAN to the DHCP
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server, it must pass along as IP number that is
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associated with one of the network (or subnet) numbers.
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The only way the DHCP server can allocate addresses on
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one of the LAN's other network (or subnet) numbers is if
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the DHCP server is specifically written to have a
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feature to handle such cases, and it has a configuration
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describing the situation.
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o The knowledge that a particular IP number is associated
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with a particular node is often used for various
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functions. Examples are: for security purposes, for
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network management, and even for identifying resources.
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Furthermore, if the DNS's names are going to identify IP
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numbers, the numbers, the IP numbers have to be stable.
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Dynamic configuration of the IP numbers undercuts such
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methods. For this reason, some sites try to keep the
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continued use of dynamically allocatable IP numbers to a
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minimum.
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o With two or more servers serving a LAN, clients that are
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moved around (e.g. mobile clients) can end up with
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redundant leases. Consider a home site with two DHCP
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servers, a remote site with DHCP services, and a mobile
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client. The client first connects to the home site and
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receives an address from one of the two serves. He/she
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then travels to the remote site (without releasing the
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lease at the home site) and attempts to use the acquired
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address. It is of course NAK'ed and the client receives
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an address appropriate for the remote site. The client
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then returns home and tries to use the address from the
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remote site. It is NAK'ed but now the client broadcasts
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a DHCPDISCOVER to get a address. The server that holds
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the previous lease will offer the address back to the
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client but there is no guarantee that the client will
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accept that address; consequently, it is possible for
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the client to acquire an address on the other server and
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therefore have two leases within the site. The problem
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can be solved by using only one server per subnet/site
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and can be mitigated by short lease lengths. But in a
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very mobile environment, it is possible for these
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transient servers to consume more than their fair share
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of addresses.
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2. Info on Implementations
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1. What features or restrictions can a DHCP server have?
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While the DHCP server protocol is designed to support dynamic
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management of IP addresses, there is nothing to stop someone
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from implementing a server that uses the DHCP protocol, but
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does not provide that kind of support. In particular, the
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maintainer of a BOOTP server-implementation might find it
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helpful to enhance their BOOTP server to allow DHCP clients
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that cannot speak "BOOTP" to retrieve statically defined
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addresses via DHCP. The following terminology has become
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common to describe three kinds of IP address
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allocation/management. These are independent "features": a
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particular server can offer or not offer any of them:
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o Manual allocation: the server's administrator creates a
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configuration for the server that includes the MAC
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address and IP address of each DHCP client that will be
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able to get an address: functionally equivalent to BOOTP
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though the protocol is incompatible.
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o Automatic allocation: the server's administrator creates
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a configuration for the server that includes only IP
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addresses, which it gives out to clients. An IP address,
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once associated with a MAC address, is permanently
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associated with it until the server's administrator
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intervenes.
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o Dynamic allocation: like automatic allocation except
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that the server will track leases and give IP addresses
|
|
whose lease has expired to other DHCP clients.
|
|
|
|
|
|
Other features which a DHCP server may or may not have:
|
|
o Support for BOOTP clients.
|
|
o Support for the broadcast bit.
|
|
o Administrator-setable lease times.
|
|
o Administrator-setable lease times on manually allocated
|
|
addresses.
|
|
o Ability to limit what MAC addresses will be served with
|
|
dynamic addresses.
|
|
o Allows administrator to configure additional DHCP
|
|
option-types.
|
|
o Interaction with a DNS server. Note that there are a
|
|
number of interactions that one might support and that a
|
|
standard set & method is in the works.
|
|
o Interaction with some other type of name server, e.g.
|
|
NIS.
|
|
o Allows manual allocation of two or more alternative IP
|
|
numbers to a single MAC address, whose use depends upon
|
|
the gateway address through which the request is
|
|
relayed.
|
|
o Ability to associate two or more dynamic address pools
|
|
on separate IP networks (or subnets) with a single
|
|
gateway address. This is the basic support for
|
|
"secondary nets", e.g. a router that is acting as a
|
|
BOOTP relay for an interface which has addresses for
|
|
more than one IP network or subnet.
|
|
o Support for User Class Information option.
|
|
o Support for Vendor Class Information option.
|
|
o Administrator-setable T1/T2 lengths.
|
|
o Interaction with another DHCP server. Note that there
|
|
are a number of interactions that one might support and
|
|
that a standard set & method is in the works.
|
|
o Use of PING (ICMP Echo Request) to check an address
|
|
prior to dynamically allocating it.
|
|
o Server grace period on lease times.
|
|
|
|
|
|
Following are some features related not to the functions that
|
|
the server is capable of carrying out, but to the way that it
|
|
is administered.
|
|
o Ability to import files listing manually allocated
|
|
addresses (as opposed to a system which requires you to
|
|
type the entire configuration into its own input
|
|
utility). Even better is the ability to make the server
|
|
do this via a command that can be used in a script,
|
|
rdist, rsh, etc.
|
|
o Graphical administration.
|
|
o Central administration of multiple servers.
|
|
2. What freeware DHCP servers are available?
|
|
|
|
(This is not necessarily a complete list)
|
|
|
|
|
|
950415 Bootp server:
|
|
Bootp 2.4.3 (not DHCP, but with the "DHCP patches" mentioned
|
|
below, can handle DHCP requests)
|
|
ftp://ftp.mc.com/pub/bootp-2.4.3.tar.Z
|
|
950425 Bootp server version 2.4.3 with "samba" DHCP patches
|
|
(does manual allocation of IP addresses)
|
|
http://www.sghms.ac.uk/~mpreston/bootp_dhcp.tar.Z
|
|
(within http://www.sghms.ac.uk/~mpreston/tools.htm")
|
|
950706 "samba" DHCP patches for bootp server:
|
|
(does manual allocation of IP addresses)
|
|
ftp://nimbus.anu.edu.au:/pub/tridge/samba/contributed/DHCP.patch
|
|
(note: I've heard that the patched server will crash if it receives
|
|
one particular optional packet, the DHCP Release packet)
|
|
950711 Patched bootp server supporting DHCP-based "automatic" allocation:
|
|
(gives addresses dynamically, but never takes them away)
|
|
ftp://ftp.ntplx.net/pub/networking/bootp/bootp-DD2.4.3.tar.gz
|
|
951219 BOOTP server and patches for DHCP
|
|
ftp://africa.geomic.uni-oldenburg.de/pub/people/joey/dhcp/bootpd/
|
|
960112 OS/2 port of BOOTP server with patches for manual DHCP support
|
|
ftp://ftp.leo.org/pub/comp/os/os2/tcpip/systools/bootpd-243-dhcp.zip
|
|
960130 Rose-Hulman Institute of Technology "Mondo-DB" LAN administration
|
|
project: modified DHCP server planned
|
|
http://www.rose-hulman.edu/~allard/Mondo-DB/index.html
|
|
950630 WIDE Project:
|
|
Akihiro Tominaga (tomy@sfc.wide.ad.jp)
|
|
WIDE Project
|
|
Keio Univ.
|
|
Japan
|
|
ftp://sh.wide.ad.jp/WIDE/free-ware/dhcp/dhcp-1.2.1.tar.gz
|
|
Check Archie for dhcp-1.2.1 because lots of sites distribute it.
|
|
Beta version:
|
|
ftp://sh.wide.ad.jp/WIDE/free-ware/dhcp/dhcp-1.3beta.tar.gz
|
|
960308 Internet Software Consortium DHCP/BOOTP Server (ISC dhcpd beta 0)
|
|
ftp://www.isc.org/pub/dhcp/DHCPD-BETA-0.tar.gz
|
|
http://www.isc.org/isc
|
|
960308 Carnegie Mellon University DHCP/BOOTP server (SunOS, dhcp-3.3.6)
|
|
ftp://ftp.net.cmu.edu/pub/dhcp/dhcp-3.3.6.tar.gz
|
|
|
|
3. What commercial DHCP servers are available?
|
|
|
|
(This is not necessarily a complete list)
|
|
|
|
|
|
950425 Silicon Graphics
|
|
950613 NetWare/IP 2.1 will NOT support DHCP but support for enhanced
|
|
bootp will be provided. I'm guessing this means DHCP-format
|
|
packets, but no address leasing.
|
|
950714 FTP Software (Services OnNet Product)
|
|
http://www.ftp.com/mkt_info/services.html
|
|
950714 Microsoft Windows NT
|
|
http://www.microsoft.com/NTServer/
|
|
http://www.microsoft.com/BackOffice/techbriefs/tech1000.htm
|
|
950714 Hewlett Packard HP-UX
|
|
950906 IBM: included in Warp Server which is in beta
|
|
951010 Wollongong: included in next release of PathWay for OpenVMS which is in
|
|
beta
|
|
951010 TGV: DHCP/BOOTP server will be included in Multinet for VMS v3.5.
|
|
http://www.tgv.com/
|
|
951121 TGV(800-848-3440): MultiNet 3.5 for OpenVMS includes DHCP server.
|
|
mailto:sales@tgv.com
|
|
http://www.tgv.com/
|
|
951207 IBM: DHCP server included in AIX 4.1.4 server packages.
|
|
Also includes custom DNS server that is "DHCP knowledgeable".
|
|
http://www.ibmlink.ibm.com/(search for DHCP in SalesManual)
|
|
951219 Puzzle Systems: WEBserv (NLM(s) that do DHCP, BOOTP, HTTP, and FTP)
|
|
mailto:info@puzzle.com
|
|
http://www.puzzle.com/
|
|
951220 ON Technology: IPTrack is a Novell Server-based DHCP/BOOTP server (NLM)
|
|
http://www.on.com/on/onprods/iptrack.html/
|
|
951220 Process Software: server for OpenVMS included in TCPware for OpenVMS
|
|
http://www.process.com/
|
|
960108 Sun Solstice LAN Management Package (SolarNet)
|
|
http://www.sun.com/cgi-bin/show?sunsoft/Products/Networking-products/pro
|
|
ducts/pcadmin.html
|
|
http://www.sun.com/cgi-bin/show?products-n-solutions/sw/solstice/network
|
|
/prod_spec_solstice_solarnet.html
|
|
960110 Quadritek Systems, Inc. (DHCP server included in next release)
|
|
http://www.qtek.com/qsi-qip.html
|
|
960130 Network TeleSystems: Shadow (PC-based)
|
|
http://www.ntsi.com/nts_shadow.html
|
|
960130 Digital: RoamAbout Mobile IP Client/Server Network Software V2.0
|
|
http://www.digital.com/info/Customer-Update/940620001.txt.html
|
|
960208 Competitive Automation's JOIN (415-321-4006): SunOS4.x, Solaris2.x,
|
|
DECOSF3.x,4.x, HP-UX 9 & 10 DHCP/BOOTP servers.
|
|
http://www.join.com/
|
|
960209 Microsoft Windows NT Server
|
|
http://www.microsoft.com/NTServer/
|
|
http://www.microsoft.com/BackOffice/techbriefs/tech1000.htm
|
|
ftp://ftp.microsoft.com/bussys/winnt/winnt-docs/papers/tcpipimp.doc
|
|
960312 Nevod Inc. Proxy IP/DHCP Server (PIP) Beta-1.0
|
|
http://www.nevod.com/pip/index.html
|
|
960327 Xedia: IP/Assist 1.0 feature for their switches includes DHCP service.
|
|
http://www.xedia.com
|
|
960328 Novell: Netware IP 2.2 includes a DHCP server.
|
|
ftp://ftp.novell.com/updates/unixconn/nwip22/nips22.exe
|
|
|
|
4. Which vendors of client software currently support DHCP?
|
|
|
|
(This is not necessarily a complete list)
|
|
|
|
|
|
950417 Shiva: proxy client for remote users (in Lanrovers and Netmodems)
|
|
950421 Microsoft: Windows for Workgroups
|
|
950425 Sun
|
|
950425 Silicon Graphics
|
|
950425 Hewlett-Packard
|
|
950502 NetManage: Chameleon 4.5
|
|
950630 Beame & Whiteside Software: resells Dirk Koeppen EDV-Beratungs-GmbH's
|
|
TCP/IP BOOT-PROM
|
|
950705 Microsoft: MS-TCP/IP 3.11a & MS-TCP/IP 3.11b
|
|
950711 Microsoft: Windows NT 3.5
|
|
950711 Microsoft: Windows for Workgroups 3.11a
|
|
950711 Frontier Technologies(800-929-3054): in SuperTCP for Windows
|
|
http:www.frontiertech.com
|
|
info@frontiertech.com
|
|
950712 Beame & Whiteside(800-720-7151): BW-Connect NFS for DOS & Windows
|
|
950725 IBM: a future release of AIX
|
|
950728 Sun: PCNFS for Windows
|
|
950802 Wollongong: PathWay Access ver 3.2 (Windows)
|
|
http://www.twg.com/
|
|
950802 WRQ: Reflection Network Series products (version 5) for Windows
|
|
http://www.wrq.com/
|
|
950814 Competitive Automation(415-321-4006): SunOS4.x, Solaris2.x and
|
|
DECOSF3.x,4.x clients
|
|
950906 IBM: included in Warp Server which is in beta
|
|
950915 Stampede: included in Remote Office Gold
|
|
951113 Persoft(800-368-5283): TCP Addition and Portable TCP
|
|
http://www.persoft.com
|
|
951207 Dirk Koeppen EDV-Beratungs-GmbH: TCP/IP DHCP Boot ROMs (TCP/IP
|
|
BOOT-PROM) www.dunkel.de/dksoft
|
|
951207 IBM: AIX 4.1.4 client and server packages include a DHCP client.
|
|
http://www.ibmlink.ibm.com/(search for DHCP in SalesManual)
|
|
951220 Attachmate: IRMA TCP Suite Version 3.1
|
|
960130 Digital: RoamAbout Mobile IP Client/Server Network Software V2.0
|
|
http://www.digital.com/info/Customer-Update/940620001.txt.html
|
|
960209 FTP Software: OnNet 2.0 (Windows)
|
|
http://www.ftp.com/
|
|
960209 FTP Software: PC/TCP 4.0 (DOS)
|
|
http://www.ftp.com/
|
|
960305 TGV: will be included in MultiNet for Windows V1.2
|
|
http://www.tgv.com/
|
|
960312 Core Systems: Internet-Connect for Windows 95 Version 2.1 has DHCP
|
|
proxy client.
|
|
http://ns1.win.net/~core/Coresys/homepage.html
|
|
960312 Novell: I heard a report that they offer a client.
|
|
960313 Apple: Open Transport 1.1 included with System 7.5.3 & runs on
|
|
68030, 68040, and PowerPC Macintoshes.
|
|
960314 Apple: Open Transport 1.1 shrink wrap version will be offered.
|
|
|
|
5. What are the DHCP plans of major client-software vendors?
|
|
|
|
Apple MacOS
|
|
MacTCP's successor, Open Transport, supports DHCP.
|
|
Open Transport 1.1 ships with System 7.5 Update 2.0
|
|
(which updates MacOS to version 7.5.3, released
|
|
March 11, 1996) and supports any 68030, 68040, or
|
|
PowerPC Macintosh. A shrink wrap version of Open
|
|
Transport is planned.
|
|
|
|
Microsoft Windows95
|
|
supports it and does not support BOOTP. I heard a
|
|
rumor that BOOTP support will be added.
|
|
|
|
Novell LAN Workplace for DOS
|
|
has plans for client support later in 1995.
|
|
|
|
IBM OS/2
|
|
will support it; I have no news on when or what
|
|
version.
|
|
|
|
6. What Routers forward DHCP requests?
|
|
|
|
(This is not necessarily a complete list).
|
|
|
|
Note that in general, these routers probably already had
|
|
BOOTP forwarding, but lacked the support for the BOOTP
|
|
broadcast flag (see "broadcast flag" under What are the
|
|
Gotcha's? above). It is likely that many other routers also
|
|
support BOOTP forwarding.
|
|
|
|
Cisco
|
|
(from Cisco FAQ) Routers running GSYS version
|
|
9.21(4) and 10.0(3) as well as later releases.
|
|
|
|
Wellfleet/Bay
|
|
(from Wellfleet FAQ) DHCP is supported by enabling
|
|
BOOTP support (with transmission and/or reception
|
|
as needed).
|
|
|
|
3Com Netbuilder
|
|
Version 7.2 software can support DHCP relaying
|
|
through the use of its generic UDP Helper service.
|
|
Version 8.0 and later officially supports DHCP.
|
|
|
|
Xyplex
|
|
Version 5.5 of their routing software supports
|
|
DHCP.
|
|
|
|
ALANTEC
|
|
The switches' "router" function has have been
|
|
handling BOOTP forwarding since around 1993.
|
|
Support for the broadcast flag introduced in a
|
|
maintenance release of 2.5 of their software and is
|
|
in version 2.6 and later.
|
|
|
|
IBM 2210
|
|
I've confirmed that Version 1 Release 2 has a BOOTP
|
|
relay agent. I haven't found out anything about
|
|
support for the broadcast flag.
|
|
|
|
7. What Routers include DHCP servers?
|
|
|
|
DHCP requires disk storage (or some other form of reliable
|
|
non-volatile storage), making the task of DHCP service
|
|
compatible with servers but incompatible with dedicated
|
|
routers. There are a number of server types that can be
|
|
configured to both route and serve DHCP (especially
|
|
all-in-one "Internet Gateways" designed to be web servers,
|
|
firewalls, etc.), but no dedicated routers.
|
|
8. What Servers forward DHCP requests?
|
|
o DHCP Relay Agent supplied with Windows NT Resource Kit
|
|
(version 3.51).
|
|
o For Novell servers, there are NLMs that forward BOOTP
|
|
requests, thus DHCP requests. The "forward BOOTP NLM" is
|
|
included in Netware 4.1. You can get this support in
|
|
Netware 3.11 and 3.12 also, but you must apply the
|
|
TCP31A.EXE patch which is located on Netwire. Here are
|
|
two such NLMs that are available online:
|
|
# ftp://netlab2.usu.edu/misc/bootpfd.zip(unsupported
|
|
Novell software, 1993)
|
|
# ftp://netlab2.usu.edu/misc/bootp311.zip(unsupported
|
|
Novell software, 1991)
|
|
9. Which implementations support or require the broadcast flag?
|
|
|
|
The broadcast flag is an optional element of DHCP, but a
|
|
client which sets it works only with a server or relay that
|
|
supports it.
|
|
o Clients
|
|
|
|
Microsoft Windows NT
|
|
DHCP client support added with version 3.5
|
|
sets the broadcast flag. Version 3.51 and
|
|
later no longer set it. The exception is in
|
|
the remote access support: it sets the flag
|
|
when it uses DHCP to acquire addresses to
|
|
hand out to its PPP clients.
|
|
|
|
tcp/ip-32 for Microsoft Windows for Workgroups (WFW)
|
|
Version 3.11a sets it, but version 3.11B
|
|
doesn't.
|
|
|
|
Microsoft Windows 95
|
|
Does not set the broadcast flag.
|
|
|
|
10. How can I run Windows 95 without a DHCP server?
|
|
|
|
Not really a DHCP question, but it has been asked a lot,
|
|
particularly by sites for which changing from BOOTP
|
|
represents a lot of work. Some choices:
|
|
o Use no server at all for the Windows 95 clients: set the
|
|
addresses in each client's setup.
|
|
o Install a non-Microsoft TCP/IP stack for Windows 95 that
|
|
supports BOOTP.
|
|
o Switch from your current BOOTP server to one that
|
|
supports both BOOTP and DHCP.
|
|
|
|
|
|
A Document that addresses this question is the Windows 95tm
|
|
Networking FAQ,
|
|
http://www-leland.stanford.edu/~llurch/win95netbugs/faq.htm
|
|
l
|
|
11. Do any servers limit the MAC addresses that may roam?
|
|
o IBM's AIX and OS/2 WARP DHCP servers.
|
|
12. What are the Gotcha's specific to various implementations?
|
|
|
|
In many cases, new releases have solved the problems that
|
|
have been identified with various DHCP implementations.
|
|
o There have been servers that are inflexible as to the
|
|
list of configuration parameters they were able to
|
|
serve. If your client requires certain parameters, you
|
|
could find such a server unusable.
|
|
o I hate to cast wide suspicions, but I've heard
|
|
occasional word on client DHCP implementations that do
|
|
not implement the entire protocol. Doing so requires
|
|
that the software module be able to wake up again after
|
|
a specified period of time and "renew the lease", i.e.,
|
|
ask to continue using the IP number. This is at least
|
|
one feature of DHCP that is very hard to implement in
|
|
some simpler systems.
|
|
o There are a number of issues regarding the patched bootp
|
|
servers. These have been reported to re DD2.4.3:
|
|
# 'When run from inetd, I had problems with "Could
|
|
not bind port" and DHCP request failure. I don't
|
|
know why, and the problem went away when bootpd is
|
|
run as a daemon.'
|
|
# 'Unless you set "dl" to some value in the bootptab
|
|
file, the DHCP lease time, renewal time and
|
|
prebinding time will be rubbish, which will cause
|
|
occasional renewal problems.'
|
|
o Early Microsoft DHCP client implementations required the
|
|
broadcast bit. Current ones do not.
|
|
o Early Apple Open Transport implementations did not
|
|
always fill out packets to BOOTP's 300-byte minimum,
|
|
thus BOOTP forwarding agents that follow the BOOTP RFC
|
|
and discard such packets end up discarding such DHCP
|
|
packets, causing some of the functions to fail. Open
|
|
Transport 1.1 fixes this.
|
|
|
|
Posted Mon Apr 1 14:17:39 EST 1996
|
|
|