Configuring Dynamic GRE Tunnels for VPNs
A VPN that travels through a non-MPLS network requires a generic routing encapsulation (GRE) tunnel. This tunnel can be either a static tunnel or a dynamic tunnel. A static tunnel is configured manually between two provider edge (PE) routers. A dynamic tunnel is configured using BGP route resolution.
When a router receives a VPN route that resolves over a BGP next hop that does not have an MPLS path, a GRE tunnel can be created dynamically, allowing the VPN traffic to be forwarded to that route. Formerly, GRE tunnels had to be established manually. Only GRE IPv4 tunnels are supported.
To configure a dynamic tunnel between two PE routers, include the dynamic-tunnels statement:
You can include this statement at the following hierarchy levels:
- [edit routing-options]
- [edit logical-systems logical-system-name routing-options]
Specify the IPv4 prefix range (for example, 10/8 or 11.1/16) for the destination network by including the destination-networks statement. Only tunnels within the specified IPv4 prefix range can be created.
You can include this statement at the following hierarchy levels:
- [edit routing-options dynamic-tunnels tunnel-name]
- [edit logical-systems logical-system-name routing-options dynamic-tunnels tunnel-name]
Specify the source address for the GRE tunnels by including the source-address statement. The source address specifies the address used as the source for the local tunnel endpoint. It can be any local address on the router (typically the router ID or the loopback address).
You can include this statement at the following hierarchy levels:
- [edit routing-options dynamic-tunnels tunnel-name]
- [edit logical-systems logical-system-name routing-options dynamic-tunnels tunnel-name]
Specify the type of tunnel to be dynamically created by including the tunnel-type statement. The only currently valid value is gre (for GRE tunnels).
You can include this statement at the following hierarchy levels:
- [edit routing-options dynamic-tunnels tunnel-name]
- [edit logical-systems logical-system-name routing-options dynamic-tunnels tunnel-name]
