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V-283869

CAT III (Low)

The Nokia Multiprotocol Label Switching (MPLS) router must be configured to synchronize Interior Gateway Protocol (IGP) and Label Distribution Protocol (LDP) to minimize packet loss when an IGP adjacency is established prior to LDP peers completing label exchange.

Rule ID

SV-283869r1203856_rule

STIG

Nokia Service Router OS 25.x Router Security Technical Implementation Guide

Version

V1R1

CCIs

CCI-000366

Discussion

Packet loss can occur when an IGP adjacency is established and the router begins forwarding packets using the new adjacency before the LDP label exchange completes between the peers on that link. Packet loss can also occur if an LDP session closes and the router continues to forward traffic using the link associated with the LDP peer rather than an alternate pathway with a fully synchronized LDP session. The MPLS LDP-IGP Synchronization feature provides a means to synchronize LDP with Open Shortest Path First (OSPF) or Intermediate System to Intermediate System (IS-IS) to minimize MPLS packet loss. When an IGP adjacency is established on a link but LDP-IGP synchronization is not yet achieved or is lost, the IGP will advertise the max-metric on that link.

Check Content

Review the router OSPF or IS-IS configuration.

Verify LDP will synchronize with the link-state routing protocol using the command below: 

- show router isis interface "TO-PE3" detail | match Ldp
Ldp Sync        : inService                       Ldp Sync Wait   : Disabled
Ldp Timer State : Disabled                        Ldp Tm Left     : 0

If the router Ldp Sync is not "inService", this is a finding.

Fix Text

Configure the MPLS router to synchronize IGP and LDP, minimizing packet loss when an IGP adjacency is established prior to LDP peers completing label exchange, as shown in the example below: 

- configure router interface "TO-PE3" ldp-sync-timer 100