Select a Default route within MPLS/VPN Network

Ha Dao · ‎11-30-2012

I have this topology:

( I use OSPF instead of EIGRP for routing between PE CE

the custommer vrf name is cusA, they have 4 sites:

CE from site 3 have 2 links to 2 PE ( one for backup). CE from site 3 has exist point to the internet

and how can i choice 1.1.1.2 is next-hop for default-route

Code:

R2:
ip route vrf cusA 0.0.0.0 0.0.0.0 9.0.0.6 10

Router bgp 7643
..........
address-family ipv4 vrf cusA
redistribute connected
redistribute static
redistribute ospf 2 vrf cusA match internal external 1 external 2
default-information originate
no auto-summary
no synchronization
exit-address-family

Code:

R3:
ip route vrf cusA 0.0.0.0 0.0.0.0 9.0.0.2 5

Router bgp 7643
..........
address-family ipv4 vrf cusA
redistribute connected
redistribute static
redistribute ospf 2 vrf cusA match internal external 1 external 2
default-information originate
no auto-summary
no synchronization
exit-address-family

Show command results:

Code:

R4#sh ip ro vrf cusA

Routing Table: cusA
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route

Gateway of last resort is 1.1.1.1 to network 0.0.0.0

     20.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
B       20.0.0.0/24 [200/0] via 1.1.1.2, 01:33:36
B       20.1.0.0/24 [200/0] via 1.1.1.1, 01:33:36
B       20.3.0.1/32 [200/61] via 1.1.1.2, 01:33:36
C       20.2.0.0/24 is directly connected, Loopback1
     9.0.0.0/30 is subnetted, 2 subnets
B       9.0.0.0 [200/0] via 1.1.1.2, 01:33:36
B       9.0.0.4 [200/0] via 1.1.1.1, 00:18:15
B    40.0.0.0/8 [200/0] via 1.1.1.1, 01:33:36
B*   0.0.0.0/0 [200/0] via 1.1.1.1, 00:18:15

R4#sh ip bgp vpnv4 vrf cusA
BGP table version is 329, local router ID is 1.1.1.3
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path
Route Distinguisher: 1:10 (default for vrf cusA)

*>i0.0.0.0 1.1.1.1 0 100 0 ?
* i 1.1.1.2 0 100 0 ?

How can i select 1.1.1.2 ?? anyone help me

shivjain · ‎11-30-2012

Hi

As per show output, default information originate is configured at R2 which is 1.1.1.1. If you want to get thedeafult router from 1.1.1.2 wihch is R3 then configure def-info-originate at r3.

regards

shivlu jain

www.mplsvpn.info

Ha Dao · ‎11-30-2012

Dear Shivlu Jain

I configed default-information originate at both R2 & R3

You can see

R4#sh ip bgp vpnv4 vrf cusA
BGP table version is 329, local router ID is 1.1.1.3
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path
Route Distinguisher: 1:10 (default for vrf cusA)

*>i0.0.0.0 1.1.1.1 0 100 0 ?
* i 1.1.1.2 0 100 0 ?

Threre are 2 next hop to reach 0.0.0.0, but 1.1.1.1 is the best, i want to change it

shivjain · ‎11-30-2012

Hi

There are two ways to get this done...

1. Being a smaller router-id 1.1.1.2 is preferred. You can select the lower router-id at R3 end.

2. When a BGP speaker receives the same route more than once it examines the local preference of the routes and the highest one wins and is considered the best route. in your case both the routes are having LP of 100. You can increase the LP of one and make it best. (I think this must work as its a long time I didn't play with BGP)

regards

shivlu jain

Raju Sekharan · ‎11-30-2012

if you would like the default-route from R2 to get prefered you can send that default-route with a local preference of 110

here is sameple config

ip prefix-list default-route permit 0.0.0.0/0

route-map export permit 10

match ip address prefix-list

set local-preference 110

!

route-map export permit 20

!

ip vrf cusA

export map export

Raju

Raju Sekharan · ‎11-30-2012

made a slight mistake in config line. Correcting it

ip prefix-list default-route permit 0.0.0.0/0

route-map export permit 10

match ip address prefix-list default-route==>>>

set local-preference 110

!

route-map export permit 20

!

ip vrf cusA

export map export

Raju

Ha Dao · ‎11-30-2012

Tks Rajs2 it works well

Could you help me another case

https://supportforums.cisco.com/message/3795839#3795839

Raju Sekharan · ‎11-30-2012

Sure. I will check it out

Raju

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