dhcp with two relay agents

[Rudy Zijlstra]

Op donderdag 30-10-2008 om 15:07 uur [tijdzone +0100], schreef Simon
Hobson:
> fadey wrote:
> >Thanks. It starts getting more clear. Basically now my question narrows
> >down to following:
> >
> >I have this setup:
> >
> >shared-network router1 {
> >   subnet router1.cable_modems {deny unknown-clients; ...}
> >   subnet router1.emtas {deny unknown-clients; ...}
> >   subnet router1.hosts1 {...}
> >   subnet router1.hosts2 {...}
> >}
> >
> >shared-network router2 {
> >   subnet router2.cable_modems {deny unknown-clients; ...}
> >   subnet router2.emtas {deny unknown-clients; ...}
> >   subnet router2.hosts1 {...}
> >}
> >
> >All router1 subnets share the same physical network. The same is true
> >for router2 subnets.
> >
> >Now there is a DHCPDISCOVER relayed from router2 with GIADDR set to
> >router2.cable_modems IP. It is an unknown-client (mac is not explicitly
> >specified in dhcpd.conf). In this case will dhcpd be "smart enough" to
> >DHCPOFFER an IP from route2.hosts1 subnet and NOT from router1.hosts*
> >subnets?
> 
> Yes, this differentiation based on GIAddr is automagic.
> 
> However, and this is something that I hope some of the cable modem 
> guys will chip with ...
> I'm not sure you need the shared network at all. It could be that the 
> cable equipment is capable of differentiating between the 
> infrastructure kit, user end cable modems, and user kit - in which 
> case I suspect the GIAddr received will be set to that of the 
> appropriate interface.

Let's see... For Arris C3 and C3 this is a configuration setting
Same for Cisco IOS (so all Cisco CMTS)
I'm pretty certain Casa can handle this as well, and Motorola BSR64K can
do it as well. 

BigBand i do not know... can check if needed. But surprised if they
cannot. 

So can be handled by approriate configuration on the CMTS. 

Cheers,

Rudy

> Either that, or yu keep the shared network and can use something like 
> vendor class to split the equipment into the appropriate subnets.
> I've only vaguely followed the cable modem threads, so hopefully 
> someone who's actually used this stuff can chirp up and fill in the 
> blanks.
>