[c-nsp] Seamless MPLS interacting with flat LDP domains

[James Bensley]

On Tue, 30 Apr 2019 at 15:04, <adamv0025 at netconsultings.com> wrote:
> > So for the ASR920, you get about 20,000 FIB entries. That's what you want
> to
> > keep your eye on to determine whether you're at a point where you need to
> > do this.
> >
> > Ideally, you would be carrying IGP and LDP in FIB. With BGP-SD, you can
> > control the number of routes you want in FIB.
> >
> Also with OSPF prefix-suppression you can reduce the OSPF footprint to mere
> loopbacks (i.e. excluding all p2p links).

Originally, I was in support of prefix-suppression however, Cisco
implemented it on IOS and IOS-XE devices for OSPF and not ISIS, and
not for either OSPF or ISIS on IOS-XR. Later they implemented it on
IOS-XR devices but for ISIS only and not OSPF. Another Cisco fail at
aligning their own features across their own products. So, since it
can't even be deployed in an all Cisco network, let alone a typical
multi-vendor network I just don't use it anymore.

Having said that, it does work, this is an example on IOS using
prefix-suppression for OSPF:
https://null.53bits.co.uk/index.php?page=ospf-inter-area-filtering

IS-IS on Cisco has a method that exist to only advertise the loopback
interface in the LSDB for IOS/XE and IOS-XR however, they are two
different methods.

IOS:
router isis
 advertise passive-only
 passive-interface Loopback0

IOS-XR:
router isis
 interface x/y
  suppressed

I've got lots of notes on OSPF and IS-IS scaling in a mixed
Juniper/Cisco environment but they're very much in draft format, I can
try and make them presentable if I get some free time / and there is
demand.

Cheers,
James.