multiple dhcp relay configuration

[tajinder.pal at wipro.com]

Hi Simon,

We can ping from vintcerf to dijkstra 192.168.2.1

No filtering problem. If we remove the Hamming machine relay works fine
and client gets the ip.

Dhcp range is also ok

Actually server is replying with range address but it is not reaching
upto Dijkstra. It is reaching upto Hamming eth1 interface but not after
that.

That's why we tried double relay and all other options.

Even we tried to peek into the packet headers using tcpdump. Following
is the output from eht1 interface of Hamming.

=========================

[root at Hamming ~]# tcpdump -i eth1 -v | grep Reply
tcpdump: listening on eth1, link-type EN10MB (Ethernet), capture size 96
bytes
09:51:34.656926 IP (tos 0x0, ttl  64, id 22143, offset 0, flags [DF],
proto: UDP
 (17), length: 328) 192.168.0.1.bootps > 192.168.2.1.bootps: BOOTP/DHCP,
Reply,
length: 300, hops:2, xid:0x9a16f10e, flags: [none]
        IP (tos 0x0, ttl  63, id 22143, offset 0, flags [DF], proto: UDP
(17), l
ength: 328) 192.168.0.1.bootps > 192.168.2.1.bootps: BOOTP/DHCP, Reply,
length:
300, hops:2, xid:0x9a16f10e, flags: [none]
29 packets captured
58 packets received by filter
0 packets dropped by kernel

==========================


Regards,

Tajinder



-----Original Message-----
From: dhcp-users-bounce at isc.org [mailto:dhcp-users-bounce at isc.org] On
Behalf Of Simon Hobson
Sent: Tuesday, November 07, 2006 7:34 PM
To: dhcp-users at isc.org
Subject: RE: multiple dhcp relay configuration

<tajinder.pal at wipro.com> wrote:
>  sorry gif could not be send, I think it is filtered by mailing list.

Yes, attachments are removed.


>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.

Can you ping from vintcerf to eth0 on dijkstra (192.168.2.1) ?

If not then you have a routing problem


Do you have any filtering anywhere ? If so, does it permit dhcp traffic
?


If you put a client (with fixed address) on client subnet, can it
communicate with vintcerf ?


When you have eliminated all the above potential problems, then it's
time to look at the dhcp config.


If you put a client on 192.168.0.x subnet, does it get a lease - or
if you don't have a range for that subnet, does the server log 'no
free leases' ?

Do you have a subnet declaration for 192.168.2.x and an available
range within it ?


If you are still having trouble, then I suggest using a packet
sniffer (I use ethereal/tethereal) to sniff for packets at various
points. Does the client send out a dhcp discover broadcast ? Does
dijkstra forward it (via unicast) to vintcerf ? Does vintcerf send
back any reply ? does it appear on the wire at the client end ?





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