Targeted LDP sessions went down post commit operations in ACX7348 device.

When some irb related config changes were made in device, some of the existing targeted LDP sessions in the device goes down and fails to come up.

The 3-way handshake mechanism of TCP connections fails and the device sends TCP reset packets to the peer.

 tcp        0      0 a.b.c.d:646       e.c.f.g:50390     SYN_RECV    -
 tcp        0      0 a.b.c.d:646       e.c.f.h:57447     SYN_RECV    -
 tcp        0      0 a.b.c.d:646       e.c.f.i:52003     SYN_RECV    -
 tcp        0      0 a.b.c.d:646       e.c.f.i:62204     SYN_RECV    -

Commit full recovers from the issue state.

The behaviour observed is due to the presence of unsupported configuration on the device.

The configuration is intended to enable support for Host Outbound Traffic Rewrite on IEEE 802.1-based networks.

Support for the relevant configuration is available starting from version 24.4R1.

set class-of-service host-outbound-traffic ieee-802.1 default 110

root@jtac-lab-re0:pfe> show host-path infodb fc-table
 
   ...   
     Fc8-To-Queue                0   
     Fc9-To-Queue                0   
     Fc10-To-Queue               0   
     Fc11-To-Queue               0   
     Fc12-To-Queue               0   
     Fc13-To-Queue               0   
     Fc14-To-Queue               0   
     Fc15-To-Queue               0   
     Host-Outbound-Fc          255   <<<<<<<<<  The ideal value should be 0 to 7.
     Host-Outbound-Queue         0   

Upon removing or deactivating the configuration, the CoS value on the FPC will be reset, causing all sessions to come back up.