[Xorp-users] Using Xorp for PIM SSM

[Bruce Simpson]

pcaldes wrote:
> ...
> The problem is that we don't know in advance what the SSM groups we 
> need to join. It is dynamic.
> While we could change the group-prefix under cand-rp{} to 232.0.0.0/8 
> to limit us to the default SSM range,
> I do not know feel I am knowledgeable about the ramifications of doing 
> that since it might still affect other multicast traffic in the cloud.

I agree, this is undesirable for many reasons.

It's a difficult one. 232/8 is the RFC 3171 SSM range. In theory if 
everything in your PIM domain is playing by the rules, advertising RP 
role for that range shouldn't matter, providing you tweak rp-priority as 
low as it can go.

Of course, if you use the administrative scope 239/8, this should be 
filtered at PIM domain borders anyway, assuming carrier follows best 
practice. However this isn't exclusively an SSM range.


> And I don't want to have to explain ... again .... why I interrupted 
> our customer traffic.... again.
>
>
> Hopefully someone who knows more about the Xorp SSM internals can let 
> us know if there is another workaround or how difficult it might be to 
> fix.

It's not really my call to say if it is behaving to spec or not at the 
moment... but I agree the issue needs to be revisited. I'm not familiar 
enough with the PIM code to say whether a simple solution is feasible or 
not.

If you can raise a Bugzilla ticket about the 'ip pim ssm range' 
functionality being missing, that would be very helpful.

>
> Do you think I should repost my original email to the xorp-hackers 
> list? I assumed they also read xorp-users and didn't want to crosspost.
>

You will probably just get me again :-)

cheers,
BMS