Virtual Private Routed Network Services
7750 SR OS Services Guide Page 1093
Figure 136: Inter-AS Option-B
This form of inter-AS VPRNs does not require instances of the VPRN to be created on the ASBR,
as in option-A, as a result there is less management overhead. This is also the most common form
of Inter-AS VPRNs used between different service providers as all routes advertised between
autonomous systems can be controlled by route policies on the ASBRs.
The third option, referred to as Option-C (Figure 137), allows for a higher scale of VPRNs across
AS boundaries but also expands the trust model between ASNs. As a result this model is typically
used within a single company that may have multiple ASNs for various reasons.
This model differs from Option-B, in that in Option-B all direct knowledge of the remote AS is
contained and limited to the ASBR. As a result, in option-B the ASBR performs all necessary
mapping functions and the PE routers do not need perform any additional functions then in a non-
Inter-AS VPRN.
IP/MPLS
Backbone
ASBR
L=P3
VRF
VRF
VRF
VRF
VRF
VRF
EBGP
L=Vx VPRN Label
L=Px BGP Next Hop
AS65534
AS65535
L=P1
ASBR
IP/MPLS
Backbone
OSSG256
VPNV4 UPD
L=V1
VPNV4 UPD
L=V2
VPNV4 UPD
L=V3
PE/32 IP
To Next Page
Loading...
