Today I am going to talk about the Inter-AS MPLS or you can say that Inter-provider MPLS option. So in this case i am taking the example on the Cisco devices. To maintain the continuity of MPLS VPN services across multiple service providers, mainly for customers who span world wide on different service providers, IETF described 3 types of options. These options are
- Option A
- Option B
- Option C
Inter-AS or Inter-Provider MPLS VPN solutions, while Cisco implemented three options (1, 2 and 3) with Cisco IOS (these options are also known in Cisco documents as 10A, 10B and 10C).
Lets start with all these option one by one. The first option is called as VRF to VRF connection between two different AS border routers and the explanation is as below.
Option A: VRF-to-VRF connections at the AS (Autonomous System) border routers
In this procedure, a PE router in one AS attaches directly to a PE router in another. The two PE routers will be attached by multiple sub-interfaces, at least one for each of the VPNs whose routes need to be passed from AS to AS.
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| Fig 1.1- Inter-AS option A |