From: Scott Morris (swm@emanon.com)
Date: Sat Apr 22 2006 - 18:53:31 GMT-3
The rule per DHCP specification (RFC) is that >IF< a client-id is sent in
the DHCP discovery packet, then matching MUST occur on that information, not
on the MAC address. And Cisco has (forever) used client-ID.
One of those irritating features. :) If you search through the archives,
you'll find a series of posts a while back where a few of us talked this
through and included lots of fun debugs isolating it, although it appears
that you've already discovered the pain! But the reason is because the spec
says "MUST".
HTH,
Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, JNCIE
#153, CISSP, et al.
CCSI/JNCI
IPExpert CCIE Program Manager
IPExpert Sr. Technical Instructor
smorris@ipexpert.com
http://www.ipexpert.com
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of John
Aitken
Sent: Saturday, April 22, 2006 5:36 PM
To: Cisco certification
Subject: DHCP Question
Can anyone help clarify a question I have on DHCP between routers, and
manual mappings.
If I have two routers, one acting as a DHCP server one as a client, both
connected on the same vlan (On a 3550) and the client ethernet interface
requiring a manual mapping I thought the configuration would be:
Server:
ip dhcp pool POOL-NAME
host a.b.c.d /24
hardware-address aaaa.bbbb.cccc
Client
Interface Fa0/0
ip address dhcp
And that would be enough, but this doesn't work. My debug output on the
server is something like:
*May 5 18:24:18.590: DHCPD: DHCPDISCOVER received from client
0063.6973.636f.2d30.3030.362e.6437.3536.2e32.3564.302d.4661.312f.30 on
interface FastEthernet0/0.
*May 5 18:24:18.590: DHCPD: Seeing if there is an internally specified pool
class:
*May 5 18:24:18.590: DHCPD: htype 1 chaddr 0006.d756.25d0
*May 5 18:24:18.590: DHCPD: remote id 020a00000a0a020100000000
*May 5 18:24:18.590: DHCPD: circuit id 00000000
*May 5 18:24:18.590: DHCPD: there is no address pool for 10.10.2.1.
*May 5 18:24:51.950: DHCPD: checking for expired leases.
*May 5 18:25:18.082: DHCPD: Sending notification of DISCOVER:
*May 5 18:25:18.086: DHCPD: htype 1 chaddr 0006.d756.25d0
*May 5 18:25:18.086: DHCPD: remote id 020a00000a0a020100000000
*May 5 18:25:18.086: DHCPD: circuit id 00000000
I can get it working by configuring a client identifier on each end :
Server
ip dhcp pool POOL-NAME
host a.b.c.d /24
client-identifier 01aa.aabb.bbcc.cc
Client
Interface Fa0/0
ip address dhcp client-id fastethernet Fa0/0
This seems somewhat long winded to me and the documentation I can find
doesn't indicate that this is the solution I should be using (Seems like an
MS solution).
Any help appreciated.
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