[Xorp-users] Need help with a multicast GRE & Cisco setup

[Daniel Spisak]

So I've got a tricky multicast setup I've been trying to get working and 
I feel like I've gone as far as I can with my limited knowledge. What we 
have basically is a situation where we have a device that takes radio 
chatter and turns it into multicast IP packets. There are potentially 
multiple users that would be talking to a central dispatch user and that 
central dispatch user also talks back to all of the remote users. In the 
diagram below dispatch is ROIP #2 and a remote user is ROIP #1.

http://i.minus.com/iNCKQpvwwAcCI.png

Because of the nature of the network connections between both users, it 
is necessary to do GRE tunnels to a common midpoint router to get 
multicast traffic across. In our case we have the ability to use a Cisco 
router for both our midpoint router as well as the dispatch side router. 
However, we are doing jitter correction for inbound packets from the 
ROIP boxes, and this is being handled by our FreeBSD ALIX box at both ends.

  This causes some complications for how to handle the inbound traffic 
at the dispatch end unless we do something like make the dispatch side 
ROIP box hang off a 3rd stub VLAN and talk to the ALIX board as its 
next-hop gateway and ensure the FreeBSD box is setup to act as a router 
for unicast and multicast traffic.

Below I've included pastebin links to the xorp configs and the cisco 
configs as well. I'm hoping someone can pipe up here with some 
suggestions as to what I'm doing wrong and how to correct it. Right now 
for example, if I try to send a single ICMP ping to the 239.0.0.1 
multicast IP from the midpoint cisco I get two responses back from the 
10.255.254.6 address.

Midpoint Cisco config: http://pastebin.com/53bxF2xU
Dispatch Cisco config: http://pastebin.com/tUYq4sbi
ROIP #1 Xorp config: http://pastebin.com/uTpK7nvT
ROIP #2 Xorp config: http://pastebin.com/iRYMLB1A

I'm still pretty green on multicast so a lot of this has been done based 
on reading up as much as I can and then tweaking things a little at a 
time, but I'm at a point now where I feel like I've lost sight of the 
solution and was hoping someone on here might have some insight as to 
how we might make this scenario work, if possible. If there is 
additional diagnostic info needed here, let me know and I will be happy 
to provide it, thanks!

-- 
Daniel Spisak
Network Engineer
dspisak at agiosat.net