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If you redistribute OSPF routes into BGP in each VRF, you do not want the OSPF routes

that point to sham links to be redistributed into BGP. If they were redistributed, multiple

BGP routes for a single OSPF route would exist: one BGP route at each endpoint of a

sham link.

Use the dont-install-routes command to prevent OSPF routes pointing to the sham link

from being installed in the IP routing table of the VRF, and thus to prevent them from

being redistributed into BGP. Forwarding still works using the MP-IBGP routes received

from the remote PE router.

Use the ttl command to configure a TTL for the remote neighbor because the neighbor

might be more than a single hop away. Use the update-source command to specify the

loopback address used as the source address for the OSPF connection to the remote

neighbor.

If you do not configure a sham link between each pair of PE routers for which a backdoor

link exists, then you need to redistribute BGP routes back into OSPF.

For more information about OSPF remote neighbors, see Remote Neighbors in the JunosE

IP, IPv6, and IGP Configuration Guide.

dont-install-routes

• Use to prevent any OSPF routes that point directly to the OSPF remote neighbor from

being installed in the IP routing table of the VR or VRF in which OSPF is running.

• Using this command avoids having many BGP routes to the same prefix by preventing

OSPF routes learned over the sham link from being redistributed back into BGP even

when you have configured redistribution of OSPF routes into BGP.

• Example

host1:pe1(config-router-rn)#dont-install-routes

• Use the no version to restore the default behavior, which installs these routes in the

relevant IP routing table.

• See dont-install-routes.

remote-neighbor

• Use to configure an OSPF remote neighbor.

• Example

host1:pe1(config-router)#remote-neighbor 10.25.100.14 area 35672

• Use the no version to remove the remote neighbor and any attributes configured for

the remote neighbor.

• See remote-neighbor.

ttl

• Use to configure a hop count by setting the value of the time-to-live field used by

packets sent to an OSPF remote neighbor.

• Specify a value in the range 1–255 seconds; the default value is 1 second.

JunosE 11.2.x BGP and MPLS Configuration Guide

Juniper JUNOSE 11.2.X BGP AND MPLS User Manual

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