Overview: Mpls Support On Ers8600 - Avaya 8600 Technical Manual

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1. Overview: MPLS Support on ERS8600

MPLS networking, based on RFC 4364, is supported beginning with the 5.0 software release for the
ERS8600 – please note that RFC 4364 obsoletes RFC 2547. This allows customer edge routers (CE
routers) connect to an ERS 8600 acting as an MPLS PE (Provider Edge) router to send their routes via a
MPLS backbone to other CE routers at different sites. There is no requirement for the CE routers at
different sites to peer with each other or knowledge of IP Virtual Private Networks (VPNs) across the
service provider's backbone. The CE router simply sends its routes to the PE router where the PE router
in turn exchanges the routes for a particular VPN among other PE routers that are attached to the IP
VPN. Please note the CE device can also be a Layer 2 switch connected to the PE router. Also note that
the P (Provider Router) nodes simply just switches MPLS labels and is not associated with the VPN
routes.
Upon receiving traffic from a CE router, the PE router will perform a route lookup in the corresponding
VRF route table. It is the responsibility of the PE router to maintain separate route tables for each VRF
and isolating the traffic into distinct VPNs. The CE router is associated with one VRF by the PE router
where the routes can be learned using static or a dynamic routing protocol such as eBGP, RIP, or OSPF.
If there is a match in the VRF route table with a BGP next-hop entry, the PE router will add the IP packet
into an MPLS label stack consisting of two labels, an inner label and an outer label. Please note that the
BGP next-hop is the circuitless IP address (CLIP) of the upstream PE router. The inner label is referred to
as the BGP-VPN or customer label and is associated with the customer VPN. The outer label is referred
to as the tunnel label (LDP) and is used by the P routers to label switch the packet through the network to
the appropriate upstream PE router. Please note that the P router has no awareness of the inner label.
Upon receiving the packet, the upstream PE router removes the top LDP label and does a lookup based
on the VPN label to determine the outgoing interface associated with the corresponding VRF. The outer
label is removed and the packet is forwarded to the CE router.
IV-VPN (MPLS) for ERS 8600 Technical Configuration Guide
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