First time relayed network

Patrick Trapp ptrapp at nex-tech.com
Sat Mar 25 01:41:39 UTC 2017


When I see those in my logs, it is because the  request is coming from a network the DHCP server is not addressing and it does not know what pool to associate the request with. I create a shared-network statement including the intended pool and the mystery network. Since I'm not providing an address for the mystery network, the network statement (where i would normally define the network) is a pair of empty braces.

I hope that makes sense - I can provide example configs later, but not at the moment. Hope it helps.

Patrick

> On Mar 24, 2017, at 7:51 PM, Tuc at Beach House <tuctboh at gmail.com> wrote:
> 
> Hi,
> 
> 
> I'm trying to figure out how to do relayed subnets within a datacenter
> owners environment and our (sorry, old) 4.1.1-38.P1 ISC DHCP server.
> Normally we allocated an interface to our machine for every subnet
> that its on, but this new network is "remote" and they won't stretch
> L2 to us.
> 
> So the normal config isn't what I'm used to, but works :
> 
>        subnet 10.14.14.0 netmask 255.255.255.0 {
> 
>               interface eth0;
>                authoritative;
>                allow booting;
>                option routers                  10.14.14.1;
>                option subnet-mask              255.255.255.0;
>                option domain-name              "cust19782.dc.example.com";
>                option domain-name-servers      10.14.2.1;
>                option ntp-servers              10.14.2.1;
>                next-server 10.14.14.11
>                filename "pxelinux.0";
>                pool {
>                        option routers                  10.14.14.1;
>                        option domain-name-servers 10.14.2.1;
>                        max-lease-time 600;
>                        range 10.14.14.200 10.14.14.254;
>                        allow unknown-clients;
>                }
>        }
> 
> 
> And the others all are the same, but with different "interface"
> statements. It is not wrapped in any sort of "shared-network"
> statement.
> 
> I'm getting valid Option 82 information, so I did :
> 
> class "EXTDHCP" {
> match if option agent.link-selection  = "10.14.18.0";
> }
> 
> And then pretty much the same except removed the "interface"
> statement, and added "allow members of "EXTDHCP";" into the pool
> statement.
> 
> However, all I keep seeing in my logs is :
> 
> dhcpd: DHCPDISCOVER from 81:9c:de:3b:61:02 via 10.14.17.2: unknown
> network segment
> 
> 10.14.17.2 is the TOR switch IP thats handling the relay. I can't seem
> to find any more in depth debug. Pointers to where I went wrong? (And
> "Using DHCPD 4.1.1" if it can't do it is acceptable)
> 
> 
> Thanks, Tuc
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