MPLS-CE Connected to PE
In this scenario the functions as an MPLS-CE (Customer Edge) network element connected to a Provider
Edge (PE) Label Edge Router (LER), which in turn connects to the MPLS core (RFC 4364). See the figure
below.
Figure 4: MPLS-CE to PE
The MPLS-CE functions like a PE router within its own Autonomous System (AS). It maintains Virtual
Routing and Forwarding (VRF) routes and exchanges VPN route information with the PE via an MP-eBGP
(Multi-Protocol-external BGP) session.
The PE is also configured with VRFs and exchanges VPN routes with other PEs in its AS via MP-iBGP
(Multi-Protocol-internal BGP) connections and the MPLS-CE via an MP-eBGP connection.
The EBGP connection allows the PE to change next-hop IP addresses and labels in the routes learned from
IBGP peers before advertising them to the MPLS-CE. The MPLS-CE in this case uses only MP-eBGP to
advertise and learn routes. Label Distribution Protocol (LDP) and Resource Reservation Protocol (RSVP) are
not required because of direct-connect EBGP peering. The MPLS-CE in this scenario pushes/pops a single
label (learned over the MP-eBGP connection) to/from the PE.
as a PE
Overview
In this scenario, the functions as a PE router sitting at the edge of the MPLS core. See the figure below.
Figure 5: as a PE
The eliminates the need for an ASBR or PE as shown in the first two scenarios. In this scenario, two main
requirements are introduced: IBGP functionality and MPLS label distribution protocols.
The can be configured to add two labels:
•
an outer label learned from LDP or RSVP-TE (RSVP-Traffic Engineering)
•
an inner label learned from MP-iBGP
This solution supports traffic engineering and QoS initiated via the .
ASR 5500 System Administration Guide, StarOS Release 21.5
242
BGP MPLS VPNs
MPLS-CE Connected to PE
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