inter-AS VPN option AB(D)

[unfraget]

Hi everybody! I've some question about inter-AS VPN option AB(D)

in article Inter-AS Option AB  says "By default, ASBR1 does not advertise the source prefix RD 2:N to ASBR2. This advertisement is suppressed as the prefix is being imported into an Option AB VRF."

why ASBR do that? why not advertise the source prefix RD 2:N?

[Harold Ritter · Accepted solution]

Hi,

ASBR1 needs to import the routes received from PE1 via iBGP VPNv4 in the corresponding VRF table. It then needs to export them with the RT corresponding to the local VRF table and advertise them to ASBR2 via eBGP VPNv4. This is the reason the iBGP VPNv4 received from PE1 are not propagated directly to ASBR2, like it is the case in InterAS option B.

Regards,