[j-nsp] Mixed Cisco/Juniper MPLS network

[Mark Tinka]

On Wednesday, August 14, 2013 06:33:42 PM Saku Ytti wrote:

> I'd only use separate blocks if I specifically have
> next-hops which MUST NOT be label switched (I don't
> have, but some prefer INET not to be label switched, so
> they run INET to different loopback than VPNv4) In your
> case, it seems it would make more sense to figure out
> what the actual problem is and then go back to
> flat/static ACL for all core loops.

To make my life simpler, I've generally created a prefix 
list which I've attached to the LDP session, that covers all 
my IPv4 allocations.

While it makes more sense to stick to prefixes that cover 
only Loopbacks and/or any interface addresses for which you 
want LDP LSP's created, this can get tricky quite quickly 
depending on how/where your network grows.

If it's any consolation, IOS only allocates LDP labels to 
IGP prefixes by default. Since (I hope) you don't carry your 
customer routes inside your IGP, you will generally only 
assign labels to infrastructure routes, i.e., backbone and 
Loopback interfaces.

Fair point, one could argue that "in-house" static routes 
pointing toward customer links will also end up with labels 
as IOS considers static routing an IGP when it comes to 
label allocation, but you generally don't run MPLS across 
customer point-to-point links anyway. How much this noise is 
an issue to you vs. lower administrative overhead when 
deploying boxes depends on your unique operational 
circumstances.

The problem comes when you've run out of space and you need 
to address new devices out of a block that wasn't in your 
filter to begin with, e.g., a new allocation from your RIR. 
This is where having a standard router/switch configuration 
helps a lot, because you can easily update the prefix lists 
via a bulk configuration upload with applications such as 
RANCID and friends, instead of going to every device hand-
at-a-time.

Hope this helps.

Cheers,

Mark.
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