Alcatel-Lucent 7950 SR User Configuration Manual page 402

Generic Commands
If multiple policy names are specified, the policies are evaluated in the order they are specified. The
first policy that matches is applied. If multiple export commands are issued, the last command
entered will override the previous command. A maximum of 5 policy names can be specified.
The no form of the command removes all policies from the configuration.
Default
no export — No export route policies specified.
Parameters
policy-name — The export route policy name. Allowed values are any string up to 32 characters long
fast-reroute
Syntax [no] fast-reroute
Context
config>router>ldp
Description
This command enables LDP Fast-Reroute (FRR) procedures. When enabled, LDP uses both the
primary next-hop and LFA next-hop, when available, for resolving the next-hop of an LDP FEC
against the corresponding prefix in the routing table. This will result in LDP programming a primary
NHLFE and a backup NHLFE into the forwarding engine for each next-hop of a FEC prefix for the
purpose of forwarding packets over the LDP FEC.
When any of the following events occurs, LDP instructs in the fast path the forwarding engines to
enable the backup NHLFE for each FEC next-hop impacted by this event:
The tunnel-down-dump-time option or the label-withdrawal-delay option, when enabled, does not
cause the corresponding timer to be activated for a FEC as long as a backup NHLFE is still available.
Note that because LDP can detect the loss of a neighbor/next-hop independently, it is possible that it
switches to the LFA next-hop while IGP is still using the primary next-hop. Also, when the interface
for the previous primary next-hop is restored, IGP may re-converge before LDP completed the FEC
exchange with it neighbor over that interface. This may cause LDP to de-program the LFA next-hop
from the FEC and blackhole traffic. In order to avoid this situation, it is recommended to enable IGP-
LDP synchronization on the LDP interface.
When the SPF computation determines there is more than one primary next-hop for a prefix, it will
not program any LFA next-hop in RTM. Thus, the LDP FEC will resolve to the multiple primary
next-hops that provide the required protection.
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composed of printable, 7-bit ASCII characters. If the string contains special characters (#, $,
spaces, etc.), the entire string must be enclosed within double quotes.
The specified name(s) must already be defined.
• An LDP interface goes operationally down, or is admin shutdown.
• An LDP session to a peer went down as the result of the Hello or Keep-Alive timer expiring.
• The TCP connection used by a link LDP session to a peer went down, due say to next-hop track-
ing of the LDP transport address in RTM, which brings down the LDP session.
• A BFD session, enabled on a T-LDP session to a peer, times-out and as a result the link LDP ses-
sion to the same peer and which uses the same TCP connection as the T-LDP session goes also
down.
• A BFD session enabled on the LDP interface to a directly connected peer, times out and brings
down the link LDP session to this peer.
7950 SR OS MPLS Configuration Guide