Label Operations - Nokia 7705 SAR-W Series Manual

MPLS Guide
For information on LDP treetrace commands for tracing ECMP paths, refer to the
7705 SAR OAM and Diagnostics Guide.
Note: LDP treetrace works best with label-IP hashing (lbl-ip) enabled, rather than label-only
(lbl-only) hashing. These options are set with the lsr-load-balancing command.
Note:
5.1.9.1
If an LSR is the ingress router for a given IP prefix, LDP programs a PUSH operation
for the prefix in the IOM. This creates an LSP ID to the Next Hop Label Forwarding
Entry (NHLFE) mapping (LTN mapping) and an LDP tunnel entry in the forwarding
plane. LDP will also inform the Tunnel Table Manager (TTM) about this tunnel. Both
the LSP ID to NHLFE (LTN) entry and the tunnel entry will have an NHLFE for the
label mapping that the LSR received from each of its next-hop peers.
If the LSR is to function as a transit router for a given IP prefix, LDP will program a
SWAP operation for the prefix in the IOM. This involves creating an Incoming Label
Map (ILM) entry in the forwarding plane. The ILM entry might need to map an
incoming label to multiple NHLFEs.
If an LSR is an egress router for a given IP prefix, LDP will program a POP entry in
the IOM. This too will result in an ILM entry being created in the forwarding plane, but
with no NHLFEs.
3HE 18686 AAAB TQZZA
• Because of the built-in timeout to dynamic ARP, the MAC address of the remote peer
needs to be renewed periodically. The flow of IP traffic resets the timers back to their
maximum values. In the case of LDP ECMP, one link could be used for transporting
user MPLS (pseudowire) traffic but the LDP session could possibly be using a different
equal-cost link. For LDPs using ECMP and for static LSPs, it is important to ensure that
the remote MAC address is learned and does not expire. Configuring static ARP
entries or running continuous IP traffic ensures that the remote MAC address is always
known. Running BFD for fast detection of Layer 2 faults or running any OAM tools with
SAA ensures that the learned MAC addresses do not expire.
• ARP entries are refreshed by static ARP and BFD, SAA, OSPF, IS-IS, or BGP.
• For information on configuring static ARP and running BFD, refer to the
7705 SAR Router Configuration Guide.

Label Operations

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