# IP and IPv6 Tunnel Routing Tables and MPLS Tunnels Overview

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.

For example, in a BGP/MPLS VPN topology, LDP or RSVP-TE adds routes to the tunnel routing table for all available tunnels. BGP performs a lookup in the tunnel routing table so that it can resolve indirect next hops.

You can clear the routes from the tunnel routing table. You might do this, for example, to reapply routing policies when the policies are changed.

#### Related Documentation

- MPLS Forwarding and Next-Hop Tables Overview
- Clearing and Refreshing IPv4 Dynamic Routes in the Tunnel Routing Table
- Clearing and Refreshing IPv6 Dynamic Routes in the Tunnel Routing Table
- Explicit Routing for MPLS Overview