[nsp] Managing outbound traffic.

[Mark Drayton]

mahesh.S (mahesh_s@stpb.soft.net) wrote:
> I need a help on the as-path attribute.
> 
> We are currently peering with two Tier 1 ISP (Sprint & Concert) we are
> getting full routes from both the provider's, but we are filtering
> routes on our end to balance our outgoing traffic.
> 
> We have applied the following as path access list :
> 
> ip as-path access-list 2 permit ^1239_[0-9]*$ with these we are
> getting around 22700 routes from sprint.
> 
> What we need is more as-path filtering options by which we would like
> to
> 
> get more than 50000 routes from sprint.
> 
> Pl suggest us on as-path,community options with which we can achieve
> this.

I would use communities from Sprint and Concert (assuming they both
support them) to only accept infrastructure and peer routes then use a
default route to each provider to balance the rest of the traffic. This
way, traffic to each ISP or one of their direct customers goes the most
direct route and the rest of the traffic balances between the two. Your
routing table will also be smaller and consume less memory.

! your ASN
router bgp 65500
 ! your Sprint neighbor
 neighbor 1.1.1.1 remote-as 1239
 neighbor 1.1.1.1 route-map sprint-in in
 neighbor 2.2.2.2 remote-as 65501          ! or whatever Concert ASN is
 neighbor 2.2.2.2 route-map concert-in in
!
ip bgp-community new-format
ip community-list 10 permit 1239:5998
ip community-list 10 permit 1239:5999
ip community-list 20 permit 65501:5998
ip community-list 20 permit 65501:5999
!
route-map sprint-in permit 10
 match community 10
!
route-map concert-in permit 10
 match community 20
!
! default routes to both providers
ip route 0.0.0.0 0.0.0.0 1.1.1.1
ip route 0.0.0.0 0.0.0.0 2.2.2.2

In this example I've used MFN's community settings; I don't know values
Sprint or Concert use or whether they even support them. MFN use
6461:5998 for routes learned from a customer and 6461:5999 for internal
routes.

Cheers,

-- 

Mark Drayton
izR Solutions Ltd