[KLUG Members] Routing issue

[Adam Williams]

> Ok maybe this is clearer :)
> I have a linux box sitting between two subnets.
> I have a subnet 192.168.3.0/24 connected to eth0 with IP  192.168.3.1.
> I have a subnet 192.168.2.0/24 connected to eth1 with IP  192.168.2.1.
> I have IP forwarding turned on and TCP traffic flows between them.
> I need to connect to a new dedicated T1 with a Cisco router/CSU/DSU at 
> each end that I have no control over. I am presented with an ethernet port 
> on the Cisco with an address of 10.7.35.1

Ah, so they determined the IP.  How are the remote nets going to learn
the router to your 192.168.x.x nets?

> On the other end of the T1 are five subnets that I don't have control of.

Gotcha, the lack of control thing is important.

> They are somehow patched together with Cisco routers and T1s as well.

For kicks, can you plug a packet-sniffer/ethereal-enabled-PC into the
router and see if routing-protocol and/or multi-cast packets are
dribbling out onto the floor?

> All the Cisco routers have dense mode multicast enabled.
> The remote subnets are 10.7.31.0/24, 10.7.32.0/24, 10.7.33.0/24, 
> 10.7.34.0/24, 10.7.36.0/24
> My thought is to put a third NIC card in the linux box and make that 
> interface 10.7.35.2. Then add some static routes to direct the flow.

Ok, makes sense.  You could also just plug it into your switch and
create an aliased interface on that subnet.  Depends how much you trust
the remote nets.

> > Doesn't the router have an ethernet port?  That would reduce a hop.
> Lost me. Yes it has an ethernet port with an address of 10.7.35.1
> I need to plug an ethernet cable into it going somewhere, so I assume into 
> the third NIC so the packets can be routed through the linux box with 
> IPtables retricting access to my LAN.

Ok.

> At each of the remote five LANs and on my local LAN are linux boxes 
> running a multicast application that connects to the same multicast group 
> as a kind of n-way party line.

So the multicast application RUNS on Linux?

> How do I patch this Cisco to my linux box that sits between my two 
> existing LANs?


1.) Investigate if it is emmiting RIP or OSPF updates.
2.) install third nic
3.) x-over cable between router & third nic
4.) configure third nic as 10.7.35.2
5.) Configure routing based upon results of #1
6.) ping/traceroute test
7.) Multicast config (the hard part of this question)

Linux Multicast HOWTO
http://www.icewalkers.com/Linux/Howto/Multicast-HOWTO.html#toc8

LinuxAdvancedRouting& Traffic Control HOWTO
http://lartc.org/howto/