multiple dhcp relay configuration

Tue Nov 7 13:58:11 UTC 2006

 sorry gif could not be send, I think it is filtered by mailing list. So
following will give some idea.

Vintcert(192.168.0.1: eth1)    dhcp server
	^
    	|
	|
Hamming (192.168.0.2: eth1; 192.168.1.1 eth2)
	^
	|
	|
Dijkstra (192.168.1.2: eth2; 192.168.2.1: eth0)  "dhcrelay 192.168.0.1"
	^
	|
	|
Nyquist ( dhcp : eth0)     dhcp client

I can ping from eth1/vintcerf to eth2/dijkstra and vice-versa.

Plz solve the problem.

Taj

-----Original Message-----
From: dhcp-users-bounce at isc.org [mailto:dhcp-users-bounce at isc.org] On
Behalf Of tajinder.pal at wipro.com
Sent: Tuesday, November 07, 2006 7:09 PM
To: dhcp-users at isc.org
Subject: RE: multiple dhcp relay configuration

Hi,

The attached GIF describes the network. Vintcerf is server and Nyquist
is client(eth0). I am running dhcrelay on Dijkstra.

I did use "dhcrelay 192.168.0.1" on Dijkstra but it is still not
working(even I tried this command simultaneously on Hamming also). I am
able to ping from eth1 on vintcert to eth2 on Dijkstra and vice versa.

I am not able to understand where some setting is lacking.

Regs,

Tajinder

-----Original Message-----
From: dhcp-users-bounce at isc.org [mailto:dhcp-users-bounce at isc.org] On
Behalf Of Glenn Satchell
Sent: Tuesday, November 07, 2006 4:58 PM
To: dhcp-users at isc.org
Subject: Re: multiple dhcp relay configuration

>Subject: multiple dhcp relay configuration
>Date: Tue, 7 Nov 2006 14:52:15 +0530
>From: <tajinder.pal at wipro.com>
>To: <dhcp-users at isc.org>
>
>Hi,
>
>I am trying to configure two relays both at different nets and one
>client and one server connecting like below
>
>
>DHCP Client  ------------------------->  DHCP Relay 1
>-------------------->   DHCP Relay 2   ----------------------->  DHCP
>Server
>            eth0       192.168.2.x     eth0         eth2    192.168.1.x
>eth2         eth1      192.168.0.x      eth1
>
>How should I give configuration so that Client can have IP address.  I
>am using open source dhcp-3.0.3 from ISC with Linux kernel 2.6
>
>I have following configuration which is not working   ( It is working
in
>case I remove one Relay)  ?
>
>Relay 1 -->
>
>dhcrelay -i eth0 -m forward 192.168.0.1(which is server)
>
>Relay -->
>
>dhcrelay -i eth2 -m append 192.168.0.1
>
>It is not working, please suggest solution.

dhcrelay needs to listen on the other interface for replies from the
dhcp server, so if you remove -i eth0 and also -m forward and -m append
you should ok.

Usually you only need something such as this on your relay hosts:

  dhcrelay 192.168.0.1

man dhcrelay
...
     The -i flag can be used to specify the network interfaces on
     which  the  relay agent should listen.   In general, it must
     listen not only on those network interfaces to which clients
     are  attached, but also on those network interfaces to which
     the server (or  the  router  that  reaches  the  server)  is
     attached.    However,  in  some cases it may be necessary to
     exclude some networks; in this case, you must list all those
     network  interfaces that should not be excluded using the -i
     flag.

As mentioned by Simon in an earlier reply, dhcrelay listens for
broadcasts then forwards them as a regular unicast packet to the dhcp
server using normal IP routing. So dhcrelay is not required on DHCP
relay 2 for packets from relay1 to get to the dhcp server.

regards,
-glenn
--
Glenn Satchell     mailto:glenn.satchell at uniq.com.au | Some days we are
Uniq Advances Pty Ltd         http://www.uniq.com.au | the flies;  some
PO Box 70 Paddington NSW Australia 2021              | days we  are the
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