Merit Network
Can't find what you're looking for? Search the Mail Archives.
  About Merit   Services   Network   Resources & Support   Network Research   News   Events   Home

Discussion Communities: Merit Network Email List Archives

North American Network Operators Group

Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical

Re: /8s and filtering

  • From: bdragon
  • Date: Tue Dec 10 13:29:06 2002

> Here is one reason for some to care :
> 
> If you want to do interdomain multicast, and your
> address space is not announced globally (say because you have a /24 that 
> is
> not from the swamp), you are likely to be black-holed
> due to RPF failures (as your unicast and multicast routing is likely to 
> be different).
> 
> This has caused problems from time to time...
> 
> Regards
> Marshall Eubanks

Until such time as vendor C determines that RPF lookups should
use the MRIB first, then the URIB, rather than the final RIB,
the following will help:

router bgp
 distance mbgp 19 19 19
ip mroute 0.0.0.0 0.0.0.0 bgp Null0 20

or if using 12.1:
router bgp
 address-family ipv4 multicast
 distance bgp 19 19 19
ip mroute 0.0.0.0 0.0.0.0 bgp Null0 20

not having looked at vendor J's multicast, I can't speak to it.

This does, however, make absolutely certain that only MBGP routes
determine RPF choices. If you expect or desire unicast routes
to drive multicast routing decisions, the above is not for you.

I had to do this to get around a bunch of RPF hedge cases.





Discussion Communities


About Merit | Services | Network | Resources & Support | Network Research
News | Events | Contact | Site Map | Merit Network Home


Merit Network, Inc.