[Xorp-users] Routing of Multicast Traffic

[Pavlin Radoslavov]

> I would like to use Xorp to simulate a ground network which is currently
> being installed. The aim is to allow lab testing of the distributed system
> before delivery. The ground network will terminate at 5 sites (each on a
> different subnet with associated gateway).
> 
> Until now I have been using monowall with a NIC for each site, with the
> card IP address set to the respective site gateway IP address. This has
> worked fine with unicast traffic, but we are now adding multicast traffic
> to the network (senders and receivers on all subnets) and monowall will
> not route multicast traffic between interfaces.
> 
> The equipment at each site will be connected with existing Cisco 3550
> Catalyst or Notel Baystack switches (all of which are currently configured
> as simple switches).
> 
> I am unsure whether I can achieve what I need to do with the LiveCD and
> simple static routes (inc. multicast static routes) or whether dynamic
> routing (PIM-Sparse with RIP or BGP) would be preferable? Each of the 5
> sites will have a single switch with connected PCs and is for an
> evaluation only, not long term installation.

First I should say that unlike unicast, for all practical reasons
there is no such thing as static multicast routing. In general,
multicast group membership is dynamic. Furthermore, static multicast
routing can be extremely dangerous: if you end-up with a multicast
routing loop this may bring-down your network.

Hence, you would have to use PIM-SM (or any other multicast routing
protocol you may like) or an alternative like IGMP snooping.
Unfortunately, I am not aware about any open-source IGMP snooping
implementation so if you choose this option you would have to go
with a proprietary implementation.

Note that if you decide to run PIM-SM you don't have to run a
dynamic unicast routing protocol like BGP or RIP: you could use
static unicast routing instead. Furthermore, you don't need to
install even unicast static routes: you could install static routes
that are used only for the purpose of multicast RPF (reverse-path
forwarding) check. See the XORP user manual for the mrib-route4 or
mrib-interface-route4 static routes setup.
The user manual should contain all other information you need
to configure XORP.
A hint: probably you don't need the dynamic PIM-SM
Bootstrap mechanism; in your case it may be simpler if you use
static Cand-RP(s).

Pavlin