Inter-AS VPN Option-C Configuration
This is an option which enables BGP VPNv4 routes exchange between the two or more Provider Edge routers residing in different AS'es. There is no VPNv4 route exchange between the ASBRs and hence the ASBRs are completely transparent of the VPNs provisioned on the connecting AS'es. This option is more scalable than the previous two options because it removes the restriction of installing VPNv4 LFIB entries on the ASBRs hence reducing the resource requirements on them. ASBRs are only required to forward data based on the transport LSPs configured.
Pre-requisites to successfully configure this option.
• There should be end to end transport LSP between the two PE's residing in different AS'es.
• Could use BGP Labeled-unicast to exchange labels for the two PE's residing in different AS'es.
• This option can utilize RR's to exchange VPNv4 routes between the two AS'es and hence should have capability to keep the next-hops unchanged when reflecting routes from iBGP to eBGP
• LDP/RSVP/SR can be used as a transport within the AS.
There are multiple ways in which this option can be configured.
• Inter-AS Option-C with VPNv4 Routes exchange between the two RRs in different AS'es
• Inter-AS Option-C with VPNv4 Routes exchange between two PE's in different AS.
• Inter-AS Option-C with VPNv4 Routes exchange between PE of one AS and RR of another AS.
This section explains the configuration for the first two points.
Last modified date: 10/17/2023