BGP Independant Domain

This feature is useful when a CE router within a VPN site peers to a PE router using iBGP. The VRF on the PE router is configured with the CE routers AS number but this AS is not carried within the AS path attribute when the customer prefixes are carried across the providers core using MP-BGP.

The reason for the above is due to the customer AS being removed from the AS path attribute and added into another attribute called ATTRSET. This effectively means that the customer AS is carried independently through the providers core and does not affect the AS path used within the providers MPLS network. When the routes arrive at a remote PE that is configured with the BGP independent domain the original customer AS is taken from the ATTRSET and replaced back into the AS path.

The following configuration is applied to the customer VRF to implement the BGP independent domain towards the customer VPN site :

routing-instances {
vpn-a {
instance-type vrf;
routing-options autonomous-system 1 independent-domain;
protocols {
bgp {
group ASN1 {
neighbor 1.1.1.2 {
local-address 10.1.1.1;
family inet {
unicast;
}
as-override;
peer-as 1;
}
}
}
}
}

 

 

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