What is the main component of Unified MPLS?
A.
Multiple IGPs in the network are used, where the loopback IP addresses of the PE routers are
aggregated on the area border routers.
B.
Confederations are used to provide scalability.
C.
The loopback prefixes from one IGP area are redistributed into BGP without changing the next
hop.
D.
The ABR is a BGP route reflector and sets next-hop to self for all reflected routes.
Since the core and aggregation parts of the network are integrated and end-to-end LSPs are
provided, the Unified MPLS solution is also referred to as “Seamless MPLS.”
New technologies or protocols are not used here, only MPLS, Label Distribution Protocol (LDP),
IGP, and BGP. Since you do not want to distribute the loopback prefixes of the PE routers from
one part of the network into another part, you need to carry the prefixes in BGP. The Internal
Border Gateway Protocol (iBGP) is used in one network, so the next hop address of the prefixes is
the loopback prefixes of the PE routers, which is not known by the IGP in the other parts of the
network. This means that the next hop address cannot be used to recurse to an IGP prefix. The
trick is to make the ABR routers Route Reflectors (RR) and set the next hop to self, even for the
reflected iBGP prefixes. In order for this to work, a new knob is needed.
Reference. http://www.cisco.com/c/en/us/support/docs/multiprotocol-label-switchingmpls/
mpls/116127-configure-technology-00.html
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