Replies to request coming over a relay goes to relay's internal IP, not to original request's source IP

[Oguz Yilmaz]

I understand what you mean. According to basic networking this does
not seem meaningful for me. DHCPD does not reply to the asking relay
server:

192.168.0.81.67 > 192.168.0.1.67: BOOTP/DHCP, Request from
00:1e:68:06:eb:37, length: 300, hops:1,
	Gateway IP: 172.16.17.81
	Client Ethernet Address: 00:1e:68:06:eb:37 [|bootp]

192.168.0.1.67 > 172.16.17.81.67: BOOTP/DHCP, Reply, length: 300, hops:1
	Your IP: 172.16.17.11
	Gateway IP: 172.16.17.81
	Client Ethernet Address: 00:1e:68:06:eb:37 [|bootp]

However, if you say this is how it works, I have nothing to say but thank you.

According to your comments a client for example 172.16.17.11 can
directly try to talk with 192.168.0.1. So we should always have right
path to 172.16.17.0 in routing table of dhcpd server.

Thank you.

--
Oguz YILMAZ


On Sat, Oct 6, 2012 at 7:17 PM, Simon Hobson <dhcp1 at thehobsons.co.uk> wrote:
> Oguz Yilmaz wrote:
>
>> HOWEVER, I have deleted route on dhcpd server to reach 172.16.17.x
>> subnet.
>
>
> Then your network setup is broken. Fix your routing tables so that the
> server can send unicast packets to devices in the 172.16.17.x subnet. Don't
> forget that clients will normally renew their leases by unicast requests
> direct to the server - so there must be a route for both the request and the
> reply.
>
> This is very basic IP networking you are getting wrong here.
>
>
> --
> Simon Hobson
>
> Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
> author Gladys Hobson. Novels - poetry - short stories - ideal as
> Christmas stocking fillers. Some available as e-books.
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