[DHCPDISCOVER]unknown network segment.
glenn.satchell at uniq.com.au
Thu Oct 16 12:19:58 UTC 2014
On Thu, October 16, 2014 10:12 pm, Simon Hobson wrote:
> Glenn Satchell <glenn.satchell at uniq.com.au> wrote:
>> The 'via' part of the log message indicates these two IPs are acting as
>> DHCP relay agents. My guess is that they are two routers with vrrp (or
>> other virtual address) advertising x.x.x.161 as the gateway.
>> What this means is that there is a subnet somewhere on the *other* side
>> these routers that is where the client is. It is this other subnet that
>> not defined so the dhcp server doesn't know how to assign an address.
>> can check this by using tcpdump to look at the packets - it will have a
>> field with the address of the gateway on that subnet.
> That's not right is it ?
> The address given in the "via ..." part should be the GI-Addr field in the
> relayed packet. By definition, that *must* be an IP address configured on
> a relay agent interface on the network to which the client is directly
> attached. If there are any other upstream relay agents, then they would
> have filled in their own GI-Addr field and either :
> 1) unicasted the packets to the server.
> 2) broadcast, but the downstream relay agent would not further mangle the
> GI-Addr field.
> A dump & decode of the packets might reveal something.
Simon, you are correct - it is the gi-addr as shown in the source code
snippet below from server/dhcp.c
log_info("%s from %s via %s: %s", s,
: "<no identifier>"),
: packet->interface->name, errmsg);
So, more likely these two devices are switches on the local network with a
dhcp relay function. Definitely need packet dumps to see what is going on.
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