[c-nsp] Asymmetric routing

[Michael Robson]

 > Michael Robson wrote:
> > Has anyone experienced asymmetric routing within their network that 
> > caused multicast RPF checks to fail and so break multicast?
> > More generally, what are people doing design-wise on their 
> networks , 
> > if anything, to avoid such problems on ever increasingly resilient, 
> > meshed networks?
> 
> Michael,
> 
> Could you be a bit more specific about the problem you're having? 
> Assuming PIM-SM, this ought not to be a problem - the normal 
> propagation of joins towards a source should build a correct oif list.
> 
> What platform are you on?
> 
There isn't a problem yet, but with multiple links out of the network and
a highly meshed network, I can reason through that it would be [almost]
impossible to avoid asymmetric routing in all cases for the network I am
currently designing. I haven't seen or heard of any real problems "in the
wild"
where multicast routing has been broken by 
asymmetric routing, but I can only see problems if 2 links out of the
network (both leading to the same network upstream but at different points)
load share the traffic, especially if topology changes (down links etc)
occur. I am trying to understand why m-RPF fails because of asymmetry isn't
an issue.

Yes we are using PIM-SM.


Michael Robson.