[j-nsp] Best practises for BGP/IGP interaction

[Tore Anderson]

Hi,

I'm setting up two data centres that'll look something like this (very 
simplified):

  IGP A1 ------------ IGP A2
    |                   |
    |                   |
  BGP A1 ------------ BGP A2
    |       Site A      |
    |      ========     |
    |       Site B      |
  BGP B1 ------------ BGP B2
    |                   |
    |                   |
  IGP B1 ------------ IGP B2

The routers marked BGP are Juniper MX-es, and terminate transit and 
peering links.  The ones marked IGP are Juniper EX-es, running VRRP on 
edge VLANs or routing things onward to other firewalls/routers/etc.  I 
don't have any route reflectors.  The IGP is OSPF.

I'm wondering if my following plans makes sense or if there's another 
set of best practises I should consider - Juniper is a bit new to me, 
still, and I kind of just picked up things as I went along with Cisco 
too..

Anyway:

1) the BGP routers will all have a 0/0 discard route they'll inject into 
OSPF, to make sure the IGP routers knows how to route to external 
destinations.  (Same as "default-information originate" in Cisco.)

Is there any other way to accomplish this, by the way?

2) the BGP routers will have configured a very high cost on the 
interfaces connected to the IGP routers.

This is to prevent iBGP sessions between, say, BGP A1 and A2 to be 
routed via IGP A1+A2 if the link between BGP A1 and A2 failed.  If that 
happened, it would cause a routing loop between BGP A1 and IGP A1 for 
packets with external destinations connected to BGP A2 (and vice verca), 
correct?

Better that the packet takes a detour via the BGP speakers in site B 
then, right?

Best regards,
-- 
Tore Anderson