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New Member

Inter-AS Option2a (Next-Hop-Self)

Hi there,

I'm trying to understand how Inter-AS Option2a ASBR to ASBR, MP-eBGP using next-hop-self command.

My findings as below. I noticed that if route-target is different from SP1 and SP2 the VPNv4 routes does not installed on respective vrf routes.

Prefix 192.168.20.0/24 is originated from PE1-AS2 belongs to same VPN in PE1-AS1.

For example:

PE1-AS1#sh ip bgp vpn all

BGP table version is 11, local router ID is 10.10.10.101

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: 1:200 (default for vrf CustomerB)

*> 192.168.1.0/30 0.0.0.0 0 32768 ?

*> 192.168.10.0 192.168.1.2 0 0 65001 i

Route Distinguisher: 2:101

*>i192.168.20.0 10.10.10.102 0 100 0 2 65001 i

Noticed that the rd/rt is configured on PE2-AS2 is completely different that PE1-AS1. If I configured to the rt same as PE1-AS1, the VPNv4 routes gets installed into vrf routing table.

PE1-AS1#

*Dec 30 22:53:17.151: BGP: Incoming path from 10.10.10.102

PE1-AS1#

*Dec 30 22:53:19.683: vpn: bgp_vpnv4_bnetinit: 1:200:192.168.20.0/24

*Dec 30 22:53:20.255: vpn: tag_vpn_find_route_tags: 1:200:192.168.20.0

*Dec 30 22:53:20.255: vpn: intag=vpn-route, outtag=24, outtag owner=BGP

PE1-AS1#sh ip bgp vpn all

BGP table version is 14, local router ID is 10.10.10.101

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: 1:200 (default for vrf CustomerB)

*> 192.168.1.0/30 0.0.0.0 0 32768 ?

*> 192.168.10.0 192.168.1.2 0 0 65001 i

*>i192.168.20.0 10.10.10.102 0 100 0 2 65001 i

Route Distinguisher: 2:101

*>i192.168.20.0 10.10.10.102 0 100 0 2 65001 i

PE1-AS1#sh ip route vrf CustomerB

Routing Table: CustomerB

Codes: C - connected, S - static, I - IGRP, 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, E - EGP

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

Gateway of last resort is not set

B 192.168.10.0/24 [20/0] via 192.168.1.2, 00:30:05

B 192.168.20.0/24 [200/0] via 10.10.10.102, 00:00:18

192.168.1.0/30 is subnetted, 1 subnets

C 192.168.1.0 is directly connected, Serial2/0

If we have Inter-AS connectivity(regardless which option), do we need the same RT/RD as well?

Thanks in advance.

1 ACCEPTED SOLUTION

Accepted Solutions
Silver

Re: Inter-AS Option2a (Next-Hop-Self)

They do not necessarily have to be the same. However, if you are using different route targets in the ASes, then you need to configure each vrf to import the route targets of the other AS. For simplicity however, you can keep the route targets the same across the AS. If not, specify them in the imports on the other AS.

What to bear in mind is that the route target determine the routes that are imported into the vrf on the configured PE. Irrespective of where the routes are coming from (either a PE in the same AS, or a neighbouring AS), the route target import configuration of the vrf would need to match route target tags for them to be immported into the vrf.

The route distiguisher does determine route imports. It serves to just ensure that the VPNv4 addresses are unique.

2 REPLIES
Silver

Re: Inter-AS Option2a (Next-Hop-Self)

They do not necessarily have to be the same. However, if you are using different route targets in the ASes, then you need to configure each vrf to import the route targets of the other AS. For simplicity however, you can keep the route targets the same across the AS. If not, specify them in the imports on the other AS.

What to bear in mind is that the route target determine the routes that are imported into the vrf on the configured PE. Irrespective of where the routes are coming from (either a PE in the same AS, or a neighbouring AS), the route target import configuration of the vrf would need to match route target tags for them to be immported into the vrf.

The route distiguisher does determine route imports. It serves to just ensure that the VPNv4 addresses are unique.

New Member

Re: Inter-AS Option2a (Next-Hop-Self)

Hi there,

Thanks for the info. I think I have found. For example right, RT might different in other SP, in order to import appropriate RT, I configured route target rewrite and works like a charm! :)

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122s/122snwft/release/122s25/fsrtrw4.htm

thank again.

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