Remote Neighbors

You can create OSPF remote neighbors to enable the router to establish neighbor adjacencies through unidirectional interfaces, such as MPLS tunnels, rather than the standard practice of using the same interface for receipt and transmission of OSPF packets. The remote neighbor can be more than one hop away through intermediate routers that are not running OSPF. OSPF uses the interface associated with the best route to reach the remote neighbor. A best route to the neighbor must exist in the IP routing table.

You must explicitly configure a remote neighbor on an OSPF router. You must specify the remote neighbor with which the router forms an adjacency and the source IP address the router uses for OSPF packets destined to its peer remote neighbor.

To form an adjacency with its remote neighbor, all OSPF packets are sent to the remote neighbor as unicast packets with the destination IP address equal to the source IP address of the remote neighbor. Use the update-source loopback command to assign the source IP address to a remote neighbor.

The connection between two remote neighbors is treated as an unnumbered point-to-point link that resides in the same area as that to which the pair of remote neighbors belongs.

The rules of OSPF adjacency must be followed for remote neighbors to form an adjacency with each other; for example, the neighbors must be in the same OSPF area and have the same hello interval and dead interval, and so on.

After you have used the remote-neighbor command to specify the remote neighbors and the update-source loopback to assign the source IP address, you must set a TTL value with the ttl command, because a remote neighbor can be more than one hop away. Configuration of all other remote-neighbor attributes is optional.

authentication-key

authentication message-digest

authentication-none

cost

dead-interval

hello-interval

message-digest-key md5

remote-neighbor

retransmit-interval

transmit-delay

ttl

update-source

Remote Neighbors and Sham Links

You can configure OSPF remote neighbors to act as sham links for BGP/MPLS VPNs. See JunosE BGP and MPLS Configuration Guide, for more information.