[c-nsp] BFD alternative

[cisconsp at SecureObscure.com]

Going unnumbered has a few advantages in a PE-P and P-P environment.
For starters, you can quickly control LFIB growth. One to one growth of
prefix / LSR, which if you run your entire mpls backbone in a big flat area
0 can help when scaling. The same can be done through filtering what
prefixes get labels generated, but that can make troubleshooting painful and
cause more harm than good.
Since there is only one ip address in the global routing table per LSR, it
makes the configuration relatively simple, cookie cutter, and I have seen it
deployed on very large scale MPLS networks successfully (ESR/GSR based, no
BFD, very few Ethernet links).
I'm sure there are some consequences as well in the IGP however I'm not the
expert so ill leave that up to others. I have spoken at length regarding
this configuration as opposed to /30s per p2p link with others and
understand the tradeoffs. We made our decision and it works well for what we
do.

John

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Lukasz Bromirski
Sent: Sunday, January 09, 2011 11:23 AM
To: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] BFD alternative

On 2011-01-09 17:40, Jason Lixfeld wrote:
> We're in the the process of turning up an MPLS network using ASR9ks
 > and ME3600s.  We're looking to get away from L2 and interconnect all
 > the devices at L3.

Wise move.

 > To facilitate this, we were originally going to use unnumbered on all
 > the PE-PE, P-P, P-PE links but we just recently discovered that BFD
 > isn't supported on unnumbered Gig/TenGig interfaces.

Why go for unnumbered? It will be harder to troubleshoot, and the
address conservation for IPv4 /30 and IPv6 /64 just doesn't make sense
unless you're really short for IPs.

-- 
"Everything will be okay in the end.  |                 Łukasz Bromirski
  If it's not okay, it's not the end." |      http://lukasz.bromirski.net
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