Alcatel-Lucent 7210 SAS M User Manual page 276

Generic Commands
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.
The no form of this command disables LDP FRR.
Default
no fast-reroute
graceful-restart
Syntax [no] graceful-restart
Context config>router>ldp
Description
This command enables graceful restart helper.
The no form of the command disables graceful restart.
Default
no graceful-restart (disabled) — Graceful-restart must be explicitely enabled.
implicit-null-label
Syntax [no] implicit-null-label
Context config>router>ldp
Description
This command enables the use of the implicit null label. Use this command to signal the IMPLICIT
NULL option for all LDP FECs for which this node is the egress LER.
The no form of this command disables the signaling of the implicit null label.
Page 276
Guide
• 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. In this case, LDP
sends a neighbor/next-hop down message to the IOM for this LDP peer only.
• 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. In this case, LDP sends a neighbor/next-hop down message to the IOM for this LDP peer
only.
• 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. In this case, LDP sends a neighbor/nexthop down mes-
sage to the IOM for this LDP peer only. BFD support on LDP interfaces is a new feature intro-
duced for faster tracking of link LDP peers.
7210 SAS M, T, X, R6, Mxp MPLS Configuration