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Label Distribution Protocol
5.3 Multicast LDP Fast Upstream Switchover
This feature allows a downstream LSR of a multicast LDP (mLDP) FEC to perform a
fast switchover in order to source the traffic from another upstream LSR while IGP
and LDP are converging due to a failure of the upstream LSR, where the upstream
LSR is the primary next hop of the root LSR for the point-to-multipoint FEC. The
feature is enabled through the mcast-upstream-frr command.
The feature provides upstream fast reroute (FRR) node protection for mLDP FEC
packets. The protection is at the expense of traffic duplication from two different
upstream nodes into the node that performs the fast upstream switchover.
The detailed procedures for this feature are described in draft-pdutta-mpls-mldp-up-
redundancy.
5.3.1 mLDP Fast Upstream Switchover Configuration
To enable the mLDP fast upstream switchover feature, configure the following option
in the CLI:
When mcast-upstream-frr is enabled and LDP is resolving an mLDP FEC received
from a downstream LSR, LDP checks for the existence of an ECMP next hop or a
loop-free alternate (LFA) next hop to the root LSR node. If LDP finds one, it programs
a primary incoming label map (ILM) on the interface corresponding to the primary
next hop and a backup ILM on the interface corresponding to the ECMP or LFA next
hop. LDP then sends the corresponding labels to both upstream LSR nodes. In
normal operation, the primary ILM accepts packets and the backup ILM drops them.
If the interface or the upstream LSR of the primary ILM goes down, causing the LDP
session to go down, the backup ILM starts accepting packets.
To use the ECMP next hop, configure the ecmp max-ecmp-routes value in the
system to be at least 2, using the following command:
To use the LFA next hop, enable LFA using the following commands (as needed):
406
config>router>ldp>mcast-upstream-frr
config>router>ecmp max-ecmp-routes
config>router>isis>loopfree-alternates
or
config>router>ospf>loopfree-alternates
Use subject to Terms available at: www.nokia.com
© 2022 Nokia.
MPLS Guide
3HE 18686 AAAB TQZZA
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