dhcp with two relay agents

[Frank Bulk]

That's the amazing thing about CMTS' - it pretty well just works.

I have the CM's in their own subnet.  The CPE and eMTAs are together in a
shared network.  I configured the CMTS as follows:
	cable helper-address a.b.c.d cable-modem global
	cable helper-address a.b.c.d host global
	cable helper-address a.b.c.d mta global
and the DHCP server figures it out correctly.

The eMTAs have host entries defined, so they don't get CPE IPs.

Frank

-----Original Message-----
From: dhcp-users-bounce at isc.org [mailto:dhcp-users-bounce at isc.org] On Behalf
Of fadey
Sent: Thursday, October 30, 2008 4:43 AM
To: dhcp-users at isc.org
Subject: Re: dhcp with two relay agents

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?


> fadey wrote:
> >Thanks for your reply. I was trying to simplify my network setup and
> >messed it up :-)
> >
> >I'm in a cable network. Behind every router I have about 3-5 different
> >networks. Thats why I use shared-network option:
> >
> >shared-network eth1 {
> >   subnet that.is.on.networkcard1 {...}
> >   subnet router1.cable_modems {...}
> >   subnet router1.emtas {...}
> >   subnet router1.hosts1 {...}
> >   subnet router1.hosts2 {...}
> >}
>
> You do NOT need a local network card for each remote subnet. Try this :
> shared-network eth1 {
>    subnet router1.cable_modems {...}
>    subnet router1.emtas {...}
>    subnet router1.hosts1 {...}
>    subnet router1.hosts2 {...}
> }
>
> Make a shared network for EACH SHARED NETWORK. A shared network is
> one where ON THE SAME BIT OF WIRE you have multiple subnets. So the
> stuff behind router1 is NOT on a shared network with stuff behind
> router2 or with stuff connected directly to the server.