Christian Meutes wrote:
Hello,
is an opinion out there about sizing/designing MVPNs with more than
255 groups per VRF? Should I use SSM for the default-mdt and abandon
PIM-SM for this purpose? The problem I see is the maximum cache size
I like SSM for default and data MDT, but unfortunately we had to drop it
so we could interoperate with Junipers (which only implement the very
new RFC, and neither of the cisco proprietary older type-2 RD or newer
MDT BGP AF)
As far as I can see, SSM would only be of specific help if the >255
groups were coming from >1 PE. You'd still have problems with >255
groups on 1 PE using SSM.
of a /24 for the data-mdt. When this limit exceeds what will exactly
Huh. I had not known that was a limit, but sure enough:
core-spare(config-vrf)#mdt data 239.192.0.0 0.0.255.255
% HASH values can not exceed 255!
happen when all streams are still active? Streaming everything over
the RP will produce bottlenecks and is something I want to avoid.
The traffic will not flow via the RP, since all the PEs should have
joined towards the other PEs for the default or data group in question.
The issue is that some traffic might be sent to PEs which have no
interest in it (if you have more active MVPN groups than data groups, or
if it's flowing in the mdt default) but it will still flow on the source
tree in the P-space, not the shared tree.
Whether that's actually a problem depends on the bit rate of the
traffic, number of PEs and types of links. Not the most helpful answer
I'm afraid.
It would be nice if Cisco would start to track the newer RFCs (hell, it
would be nice if they'd get it out of draft and into proposed standard)
where the "all BGP" MVPNs might help in this case.
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