Description

High CCM packet for CFM with "interface-status-tlv down" both end  when disabled/enabled OAM protocol.

PRODUCT:- MX240/mx480/960
version:- 21.2R3-S4

                    
lab@R01> show oam ethernet connectivity-fault-management interfaces xe-1/0/9.0 extensive
<SNIP>
CCMs sent : 4243385


 

Symptoms

Customer observing huge CCM packets after configuring " interface-status-tlv down".

Customer is using below configuration both end
 

action-profile bring-down {

           event {

               interface-status-tlv down;         <<<<

               adjacency-loss;

           }

           action {

               interface-down;

           }

       }




logs

user1@R1-re0> show oam ethernet connectivity-fault-management interfaces et-2/0/0.0 extensive | match "CCMs sent" | refresh 1
      CCMs sent                                     : 0
---(refreshed at 2023-10-19 01:33:09 PDT)---
      CCMs sent                                     : 1161
---(refreshed at 2023-10-19 01:33:10 PDT)---
      CCMs sent                                     : 3555
---(refreshed at 2023-10-19 01:33:11 PDT)---
      CCMs sent                                     : 6267
---(refreshed at 2023-10-19 01:33:12 PDT)---
      CCMs sent                                     : 9018
25 PDT)---
      CCMs sent                                     : 45303

Solution

This is known limitation and There is already a planned RLI which is currently scheduled for 24.3R1.

Configuring interface-status-tlv down on both the routers is a product limitation which is leading to a deadlock scenario where the interface would be continuously flapping as during recovery phase when the peer is activated, it would be receiving interface status tlv down from DUT (as peer was previously deactivated) and then peer would also start sending interface-status-down tlv down.
 

Due to above back and forth messages of IFL interface state, the IFL would be continuously flapping, and any change in IFL state would lead to PDU change. Hence we see high PPS of CCM sent.

 

 

 

Modification History

2023-11-22 : Article Created