[c-nsp] DHCP relay still forwarding to old helper even if it's removed or changed

Peter Rathlev peter at rathlev.dk
Tue Jan 20 03:01:47 EST 2015

On Mon, 2015-01-19 at 21:18 +0200, Tarko Tikan wrote:
> > I tried to change the helper address, but after making the change,
> > the box was still routing broadcasts to the old helper.
> Are you 100% sure it's actually relayed traffic and not DHCP client
> that remembers DHCP server address and unicasts the request?

On Mon, 2015-01-19 at 19:20 -0500, Jason Lixfeld wrote:
> The lease timer is 3 minutes, so if after 4 minutes it’s still trying
> to reach the old server, it shouldn’t be a client-side problem.  That
> said, I’ll reboot a client tomorrow and see what happens.

As long as the client can actually renew the lease it will continue to
unicast requests to the old server. So unless the scope is disabled on
the old server (making it reply with NAKs or not reply) they will not
move to the new server.

Are you actually seeing DISCOVERs on the old server? Or just REQUESTs?
(Takes a server that actually logs this to find out of course.)


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