■ A spoof check field that specifies the type of spoof checking is performed to
determine whether the MPLS packet arrived from a legitimate source. See “Spoof
Checking MPLS Packets” on page 225 for more information.
Related Topics ■ See Monitoring MPLS on page 315, for information about enabling statistics
collection for MPLS forwarding table entries.
■ MPLS Label Switching and Packet Forwarding on page 209
■ MPLS Label Distribution Methodology on page 218
■ Spoof Checking MPLS Packets on page 225
■ IP and IPv6 Tunnel Routing Tables and MPLS Tunnels on page 225
Spoof Checking MPLS Packets
The MPLS forwarding table enables MPLS to determine whether an MPLS packet
received from an upstream neighbor contains an MPLS label that was advertised to
that neighbor. If not, the packet is dropped. Each entry in the forwarding table has
a spoof check field that specifies the type of checking that must be performed for
the associated in label. The signaling protocol (BGP, LDP, or RSVP) that populates
the entry in the MPLS forwarding table sets the spoof check field.
MPLS supports the following types of spoof checking:
■ Router spoof checking—MPLS packets are accepted only if they arrive on an
MPLS major interface that is in the same virtual router as the MPLS forwarding
table.
■ Interface spoof checking—MPLS packets are accepted only if they arrive on the
particular MPLS major interface identified in the spoof check field.
You can use the show mpls forwarding command to view the spoof check field for
an MPLS forwarding table entry.
Related Topics ■ MPLS Forwarding and Next-Hop Tables on page 224
IP and IPv6 Tunnel Routing Tables and MPLS Tunnels
The IP and IPv6 tunnel routing tables contain routes that point only to tunnels, such
as MPLS tunnels. The tunnel routing table is not used for forwarding. Instead, protocols
resolve MPLS next hops by looking up the routes in the table. For example, BGP uses
the table to resolve indirect next hops for labeled routes.
BGP, LDP, and RSVP-TE can contribute routes to the table. LDP adds all destinations
that can be reached by means of labels learned from downstream LDP neighbors.
RSVP-TE adds only MPLS tunnel endpoints. BGP also adds routes to the tunnel table
in certain cases. Routes added by any of these protocols include the effective metric.
Spoof Checking MPLS Packets ■ 225
Chapter 2: MPLS Overview
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