[c-nsp] IOS XR BGP

[Keegan Holley]

2011/11/28 Mark Tinka <mtinka at globaltransit.net>

> On Tuesday, November 29, 2011 12:06:28 AM Keegan Holley
> wrote:
>
> >  It's cleaner to have a route type for aggregates than a
> > static null0 route with the same default preference of a
> > static route.
>
> Why would it be cleaner?
>
> The static route is basically used to pull-up the aggregate
> into BGP. This points to a Null interface on all BGP-
> speaking routers, ensuring packets that arrive for subnets
> not in iBGP or the IGP get dropped, and also announcing said
> routes to eBGP neighbors.
>
> Works. Simple. Effective.
>

You can also apply attributes directly to the aggregate.  So you can set
origin code, local pref etc. directly on the route.  Also, from the
non-technical side it's cleaner to know it's an aggregate as opposed to a
static route doing something else.

>
> > Another is not having eBGP routes
> > preferred over iBGP route.
>
> Your aggregates would be in your iBGP. Would you expect to
> learn your aggregates from outside your routing domain?
>

That wasn't centered around aggregates and no.  Some of us don't run
gigantic intercontinental ISP's :) So yes us lowly Tier-II and Tier-III
AS's may on occasion learn our own routes from an external connection.
 Also, just because the AS number is different doesn't mean it's not yours.
 It's better (and I fully admit that this is debatable) to have the iBGP
vs. eBGP choice much lower in the selection process..

>
> > At the risk of starting yet
> > another trite cisco vs. juniper thread, what do you mean
> > by preferred device?
>
> What I meant is if we were comparing a Cisco and a Juniper
> and the Cisco turned to be more preferred save for this one
> feature the Juniper had.
>

Agreed, this is a nothing feature.

>
> I wasn't implying Cisco are better than Juniper, or vice
> versa.
>
> Actually I was.  6509/Nexus vs. EX8200, Cisco ME vs. EX4200, ASR vs. M/MX
and CRS vs. T/TX are all different conversations.  I thought you were
alluding to something like that which I would have agreed with.