About BFD flapping

Created: Aug 21, 2018 16:00:03Latest reply: Aug 21, 2018 16:16:52 340 1 0 0
  Rewarded Hi-coins: 0 (problem resolved)
本帖最后由 kracey 于 2018-08-21 16:03 编辑 Why all bfd session will down in the same time thanks a lot.

configration: bfd hzaliyun-1 bind peer-ip 192.168.123.10 interface Vlanif2701 source-ip 192.168.123.9 one-arm-echo discriminator local 8002 min-echo-rx-interval 200 commit # bfd hzidc-1 bind peer-ip 10.11.255.34 interface Vlanif1100 source-ip 10.11.255.33 one-arm-echo discriminator local 8000 min-echo-rx-interval 200 commit # bfd hzidc-2 bind peer-ip 10.11.255.38 interface Vlanif2200 source-ip 10.11.255.37 one-arm-echo discriminator local 8001 min-echo-rx-interval 200 commit # ip route-static 0.0.0.0 0.0.0.0 10.11.255.2 ip route-static 10.10.10.0 255.255.255.0 10.11.255.34 track bfd-session hzidc-1 description hzidc-1 ip route-static 10.10.10.0 255.255.255.0 10.11.255.38 track bfd-session hzidc-2 description hzidc-2 ip route-static 172.24.0.0 255.255.0.0 192.168.123.10 track bfd-session hzaliyun-1 description HZALIYUN-1 ip route-static 172.24.0.0 255.255.0.0 10.11.255.34 preference 100 track bfd-session hzidc-1 description HZIDC-HZALIYUN-1 ip route-static 172.24.0.0 255.255.0.0 10.11.255.38 preference 100 track bfd-session hzidc-1 description HZIDC-HZALIYUN-2 log: Aug 19 2018 11:38:46 SHWG-501-G15G14-Core %BFD/4/STACHG_TOUP(l)[4]:BFD session changed to Up. (SlotNumber=0/0, Discriminator=8001, FormerStatus=Init, Applications=None, BindInterfaceName=Vlanif2200, ProcessPST=False) Aug 19 2018 11:38:45 SHWG-501-G15G14-Core %BFD/4/STACHG_TOUP(l)[5]:BFD session changed to Up. (SlotNumber=0/0, Discriminator=8000, FormerStatus=Init, Applications=None, BindInterfaceName=Vlanif1100, ProcessPST=False) Aug 19 2018 11:38:36 SHWG-501-G15G14-Core %BFD/4/STACHG_TOUP(l)[6]:BFD session changed to Up. (SlotNumber=0/0, Discriminator=8002, FormerStatus=Init, Applications=None, BindInterfaceName=Vlanif2701, ProcessPST=False) Aug 19 2018 11:32:26 SHWG-501-G15G14-Core %BFD/4/STACHG_TODWN(l)[7]:BFD session changed to Down. (SlotNumber=0/0, Discriminator=8002, Diagnostic=DetectDown, Applications=None, ProcessPST=False, BindInterfaceName=Vlanif2701, InterfacePhysicalState=Up, InterfaceProtocolState=Up) Aug 19 2018 11:32:26 SHWG-501-G15G14-Core %BFD/4/STACHG_TODWN(l)[8]:BFD session changed to Down. (SlotNumber=0/0, Discriminator=8000, Diagnostic=DetectDown, Applications=None, ProcessPST=False, BindInterfaceName=Vlanif1100, InterfacePhysicalState=Up, InterfaceProtocolState=Up) Aug 19 2018 11:32:26 SHWG-501-G15G14-Core %BFD/4/STACHG_TODWN(l)[9]:BFD session changed to Down. (SlotNumber=0/0, Discriminator=8001, Diagnostic=DetectDown, Applications=None, ProcessPST=False, BindInterfaceName=Vlanif2200, InterfacePhysicalState=Up, InterfaceProtocolState=Up)
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StarOfWest  Visitor   Created Aug 21, 2018 16:16:52 Helpful(0) Helpful(0)

Hello,

If we check the reason from the log- Diagnostic=DetectDown  - it means the local end enters the Down state when the detection expires because it does not receive BFD packets from the remote end.
Since you enable echo-arm function, it looks like the packets go out of the local end, but it doesn't return.

Since all session go down in the same time, I suspect a physical interruption along the path that converges all 3 session, maybe on the uplink.

So when it happens again, try to ping the remote end of the line, or keep a continuous ping and see whether there are packet losses over that path.
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“We only get answers to the questions that we ask.” physicist Werner Heisenberg

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