Specifications

10-31
Cisco IGX 8400 Series Provisioning Guide, Release 9.3.3 and Later Releases
OL-1166-04
Chapter 10 Cisco IGX 8400 Series IP Service
IP Service—Functional Overview
BGP propagates vpnv4 information using the BGP Multi-Protocol extensions for handling these
extended addresses (see RFC 2283, Multi-Protocol Extensions for BGP-4). BGP propagates reachability
information (expressed as VPN-IPv4 addresses) among PE routers; the reachability information for a
specific VPN is propagated only to other members of that VPN. The BGP Multi-Protocol extensions
identify the valid recipients for VPN routing information. All members of the VPN learn routes to other
members.
MPLS Label Forwarding
Based on the routing information stored in the IP routing table and the CEF table for each VRF, Cisco
label switching uses extended VPN-IPv4 addresses to forward packets to their destinations.
An MPLS label is associated with each customer route. The PE router assigns the label that originated
the route, and directs the data packets to the correct CE router.
Label forwarding across the provider backbone is based on either dynamic IP paths or Traffic
Engineered paths. A customer data packet has two levels of labels attached when it is forwarded across
the backbone.
• The top label directs the packet to the correct PE router.
• The second label indicates how that PE router should forward the packet.
The PE router associates each CE router with a forwarding table that contains only the set of routes that
should be available to that CE router.
no auto-summary
redistribute static
exit-address-family
!
address-family ipv4 unicast vrf vrf2
neighbor 10.20.1.11 activate
no auto-summary
redistribute static
exit-address-family
!
! Define a VRF static route
ip route vrf vrf1 12.0.0.0 255.0.0.0 e5/0/1 10.20.0.60
Virtual Circuit Merge on the IGX
Note VC merge on the IGX is not supported in releases preceding Switch Software Release 9.3.40.
Virtual circuit (VC) merge on the IGX improves the scalability of MPLS networks by combining
multiple incoming VCs into a single outgoing VC (known as a merged VC). VC merge is implemented
as part of the output buffering for the ATM interfaces found on the UXM-E. Each VC merge is
performed in the egress direction for the connections.
Both interslave and intraslave connections are supported. However, neither the OAM cell format nor
tagABR for the MPLS controller are supported.
Note VC merge is not supported on the UXM card.