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Label Distribution Protocol
mcast-upstream-frr
Syntax
[no] mcast-upstream-frr
Context
config>router>ldp
Description
This command enables the mLDP fast upstream switchover feature.
When this command is enabled and LDP is resolving an mLDP FEC received from a
downstream LSR, it checks whether an ECMP next hop or an LFA next hop to the root LSR
node exists. If LDP finds one, it programs a primary 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. Then, LDP sends the corresponding labels to both upstream LSR nodes. Under normal
operation, the primary ILM accepts packets while 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.
In order to make use of the ECMP next hop, the user must configure the ecmp value in the
system to at least "2", using the following command:
config>router>ecmp
In order to make use of the LFA next hop, the user must enable LFA using the following
commands (as needed):
config>router>isis>loopfree-alternates
config>router>ospf>loopfree-alternates
Enabling the IP FRR or LDP FRR feature is not strictly required since LDP only needs to know
the location of the alternate next hop to the root LSR so it can send the Label Mapping
message to program the backup ILM at the initial signaling of the tree. Therefore, enabling
the LFA option is sufficient. However, if unicast IP and LDP prefixes need to be protected,
then these features and the mLDP fast upstream switchover can be enabled concurrently.
The mLDP FRR fast switchover relies on the fast detection of a loss of an LDP session to the
upstream peer to which the primary ILM label had been advertised. It is strongly
recommended that the following be performed:
Step 1.
Step 2.
468
Enable BFD on all LDP interfaces to upstream LSR nodes. When BFD detects the
loss of the last adjacency to the upstream LSR, it will immediately bring down the
LDP session, which will cause the CSM to activate the backup ILM.
If there is a concurrent T-LDP adjacency to the same upstream LSR node, enable
BFD on the T-LDP peer in addition to enabling it on the interface.
© 2022 Nokia.
Use subject to Terms available at: www.nokia.com
MPLS Guide
3HE 18686 AAAB TQZZA
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