Reset Search
 

 

Article

BFD session DOWN messages seen when the “Rx” & “Tx” intervals are configured within 200ms

« Go Back

Information

 
TitleBFD session DOWN messages seen when the “Rx” & “Tx” intervals are configured within 200ms
Symptoms
  • If the switches are configured with BFD and the BFD configured vlan ports are added in sharing group. 
  • When the BFD “Rx” and “Tx” intervals are configured within 200 milliseconds and if we disable the sharing group master port, switch will generate log message stating BFD session “DOWN”. However, the “show bfd” output showing the status “UP”.
  • We can configure the log filter to collect the BFD session state change notifications. 
  • When the switches configured with following BFD configuration “configure bfd vlan "test" receive-interval 200 transmit-interval 200”, we can see BFD session state change log messages.​ Please refer the below mentioned error log messages:
* SW-1-BFD.30 # show log
01/02/2017 05:46:08.38 <Info:BFD.SessnStateChg> BFD Session with srcIP=10.10.10.1 dstIP=10.10.10.2 in VR=VR-Default state is now UP
01/02/2017 05:46:07.92 <Info:BFD.SessnStateChg> BFD Session with srcIP=10.10.10.1 dstIP=10.10.10.2 in VR=VR-Default state is now DOWN
01/02/2017 05:46:07.49 <Info:LACP.RemPortFromAggr> Remove port 1 from aggregator
01/02/2017 05:46:07.49 <Info:vlan.dbg.info> Port 1 is Down, remove from aggregator 1
01/02/2017 05:46:07.49 <Info:vlan.msgs.portLinkStateDown> Port 1 link down
01/02/2017 05:44:57.98 <Info:LACP.AddPortToAggr> Add port 2 to aggregator
01/02/2017 05:44:57.97 <Info:vlan.msgs.portLinkStateUp> Port 2 link UP at speed 1 Gbps and full-duplex
01/02/2017 05:44:24.33 <Info:LACP.RemPortFromAggr> Remove port 2 from aggregator
01/02/2017 05:44:24.33 <Info:vlan.dbg.info> Port 2 is Down, remove from aggregator 1
01/02/2017 05:44:24.33 <Info:vlan.msgs.portLinkStateDown> Port 2 link down
A total of 10 log messages were displayed.

                
* SW-2-BFD.16 # show log
01/02/2017 05:45:16.05 <Info:BFD.SessnStateChg> BFD Session with srcIP=10.10.10.2 dstIP=10.10.10.1 in VR=VR-Default state is now UP
01/02/2017 05:45:15.78 <Info:LACP.RemPortFromAggr> Remove port 1 from aggregator
01/02/2017 05:45:15.78 <Info:vlan.dbg.info> Port 1 is Down, remove from aggregator 1
01/02/2017 05:45:15.78 <Info:vlan.msgs.portLinkStateDown> Port 1 link down
01/02/2017 05:45:15.53 <Info:BFD.SessnStateChg> BFD Session with srcIP=10.10.10.2 dstIP=10.10.10.1 in VR=VR-Default state is now DOWN
01/02/2017 05:44:05.53 <Info:LACP.AddPortToAggr> Add port 2 to aggregator
01/02/2017 05:44:05.52 <Info:vlan.msgs.portLinkStateUp> Port 2 link UP at speed 1 Gbps and full-duplex
01/02/2017 05:43:32.63 <Info:LACP.RemPortFromAggr> Remove port 2 from aggregator
01/02/2017 05:43:32.63 <Info:vlan.dbg.info> Port 2 is Down, remove from aggregator 1
01/02/2017 05:43:32.63 <Info:vlan.msgs.portLinkStateDown> Port 2 link down
A total of 10 log messages were displayed.
  • Switches configured with following BFD configuration “configure bfd vlan "test" receive-interval 300 transmit-interval 300”, we are not seeing BFD session state change log messages.

* SW-1-BFD.65 # show log
01/02/2017 05:56:23.11 <Info:LACP.RemPortFromAggr> Remove port 1 from aggregator
01/02/2017 05:56:23.11 <Info:vlan.dbg.info> Port 1 is Down, remove from aggregator 1
01/02/2017 05:56:23.11 <Info:vlan.msgs.portLinkStateDown> Port 1 link down
01/02/2017 05:56:04.22 <Info:LACP.AddPortToAggr> Add port 2 to aggregator
01/02/2017 05:56:04.16 <Info:vlan.msgs.portLinkStateUp> Port 2 link UP at speed 1 Gbps and full-duplex
01/02/2017 05:54:56.43 <Info:LACP.RemPortFromAggr> Remove port 2 from aggregator
01/02/2017 05:54:56.43 <Info:vlan.dbg.info> Port 2 is Down, remove from aggregator 1
01/02/2017 05:54:56.43 <Info:vlan.msgs.portLinkStateDown> Port 2 link down
A total of 8 log messages were displayed.

* SW-2-BFD.38 # show log
01/02/2017 05:55:31.06 <Info:LACP.RemPortFromAggr> Remove port 1 from aggregator
01/02/2017 05:55:31.06 <Info:vlan.dbg.info> Port 1 is Down, remove from aggregator 1
01/02/2017 05:55:31.06 <Info:vlan.msgs.portLinkStateDown> Port 1 link down
01/02/2017 05:55:11.79 <Info:LACP.AddPortToAggr> Add port 2 to aggregator
01/02/2017 05:55:11.76 <Info:vlan.msgs.portLinkStateUp> Port 2 link UP at speed 1 Gbps and full-duplex
01/02/2017 05:54:04.38 <Info:LACP.RemPortFromAggr> Remove port 2 from aggregator
01/02/2017 05:54:04.38 <Info:vlan.dbg.info> Port 2 is Down, remove from aggregator 1
01/02/2017 05:54:04.38 <Info:vlan.msgs.portLinkStateDown> Port 2 link down
01/02/2017 05:50:57.92 <Info:LACP.AddPortToAggr> Add port 1 to aggregator
01/02/2017 05:50:57.90 <Info:vlan.msgs.portLinkStateUp> Port 1 link UP at speed 1 Gbps and full-duplex
A total of 10 log messages were displayed.

Environment
  • Summit X450G2-24t-10G4
  • EXOS 21.1.1.4 patch1-5
Cause
Resolution
The behavior is expected due to time taken for the link detection event. 

Please find below the explanation:
  • On disabling LAG master port , copper link down detection itself is taking 600ms to 1 sec . 
  • During the link down detection event, switch won’t send/receive BFD PDU until it switches to member port of LAG group.
  • When configuring  200 milliseconds, the BFD PDU’s won’t  be exchanged for 600 ms and declares BFD session as down.
On increasing the hello intervals to 300+ ms, this behavior cannot be observed since link detection event will be completed before exchanging 3 BFD PDU’s. 
Also, with fiber link the behavior cannot be observed even with 100 ms since link detection is faster for fiber ports.
  • Please contact GTAC for further assistance.

 
Additional notes

Feedback

 

Was this article helpful?


   

Feedback

Please tell us how we can make this article more useful.

Characters Remaining: 255