시스코 스위치 link-flap 에러 처리

시스코 스위치 link-flap 에러 처리

상태 : C3550 스위치 포트가 link-flap 에러를 감지하고, 포트 상태를 err-disabled 상태로 변경함. 39번 포트에 연결된 장비는 통신이 안되는 상황 발생.
link-flap 은 인터페이스(스위치포트)가 up/down 을 반복하는 것을 의미한다.

먼저, 스위치 로그를 확인해 본다.

Switch #show log
...
May 28 07:38:16: %LINK-3-UPDOWN: Interface FastEthernet0/39, changed state to up
May 28 07:38:18: %PM-4-ERR_DISABLE: link-flap error detected on Fa0/39, putting Fa0/39 in err-disable state
May 28 07:38:18: %LINK-3-UPDOWN: Interface FastEthernet0/39, changed state to down

...

포트 상태를 확인해 보면, 39번 포트는 err-disabled 상태이다.

Switch # show int status

Port Name Status Vlan Duplex Speed Type
Fa0/1 connected trunk a-full a-100 10/100BaseTX
...
Fa0/38 notconnect 1 auto auto 10/100BaseTX
Fa0/39 err-disabled 1 auto auto 10/100BaseTX
Fa0/40 notconnect 1 auto auto 10/100BaseTX
Fa0/41 notconnect 1 auto auto 10/100BaseTX
...

10초동안 5번 flap발생하면, 스위치 포트는 err-disabled 상태가 된다.
flap-vlaue값은 아래 명령어로 확인 가능하다.

Switch #show errdisable flap-values
ErrDisable Reason Flaps Time (sec)
----------------- ------ ----------
pagp-flap 3 30
dtp-flap 3 30
link-flap 5 10

일단, 인터페이스를 down, up 하여 해당 포트를 이용 가능하도록 할 수 있다.

Switch # conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch (config)#int fa0/39
Switch (config-if)#shutdown
May 28 10:40:32: %LINK-5-CHANGED: Interface FastEthernet0/39, changed state to administratively down.
Switch (config-if)#no shutdown
Switch (config-if)#end

동일한 현상이 다시 발생할경우를 대비하여 자동으로 포트가 복구되도록 설정한다.

err-disable 검출은 아래 항목들이 enabled 되어 있음.

Switch #show errdisable detect
ErrDisable Reason Detection Mode
----------------- --------- ----
arp-inspection Enabled port
bpduguard Enabled port
channel-misconfig Enabled port
community-limit Enabled port
dhcp-rate-limit Enabled port
dtp-flap Enabled port
ekey Enabled port
gbic-invalid Enabled port
invalid-policy Enabled port
l2ptguard Enabled port
link-flap Enabled port
link-monitor-failure Enabled port
loopback Enabled port
lsgroup Enabled port
oam-remote-failure Enabled port
mac-limit Enabled port
pagp-flap Enabled port
port-mode-failure Enabled port
psecure-violation Enabled port/vlan
security-violation Enabled port
sfp-config-mismatch Enabled port
storm-control Enabled port
udld Enabled port
unicast-flood Enabled port
vmps Enabled port
Switch #

errdisable 상태에서 recovery 상태를 보면, disable 되어 있음.

Switch #show errdisable recovery
ErrDisable Reason Timer Status
----------------- --------------
arp-inspection Disabled
bpduguard Disabled
channel-misconfig Disabled
dhcp-rate-limit Disabled
dtp-flap Disabled
gbic-invalid Disabled
l2ptguard Disabled
link-flap Disabled
mac-limit Disabled
link-monitor-failure Disabled
loopback Disabled
oam-remote-failure Disabled
pagp-flap Disabled
port-mode-failure Disabled
psecure-violation Disabled
security-violation Disabled
sfp-config-mismatch Disabled
storm-control Disabled
udld Disabled
unicast-flood Disabled
vmps Disabled

Timer interval: 300 seconds

Interfaces that will be enabled at the next timeout:

link-flap으로 포트가 err-disabled 상태가 되었을때, 30초후 자동 복구 되도록 설정한다.

Switch #conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch (config)#errdisable recovery cause link-flap
Switch (config)#errdisable recovery interval 30
Switch (config)#end

아래처럼 link-flap으로 인한 오류는 자동으로 복구되도록 설정된 것을 볼 수 있다.

Switch #sh errdisable recovery
ErrDisable Reason Timer Status
----------------- --------------
arp-inspection Disabled
bpduguard Disabled
channel-misconfig Disabled
dhcp-rate-limit Disabled
dtp-flap Disabled
gbic-invalid Disabled
l2ptguard Disabled
link-flap Enabled
mac-limit Disabled
link-monitor-failure Disabled
loopback Disabled
oam-remote-failure Disabled
pagp-flap Disabled
port-mode-failure Disabled
psecure-violation Disabled
security-violation Disabled
sfp-config-mismatch Disabled
storm-control Disabled
udld Disabled
unicast-flood Disabled
vmps Disabled

Timer interval: 30 seconds

Interfaces that will be enabled at the next timeout:

Switch #

동일한 시간동안 더 많은 link-flap을 감지해야 err-disabled 되도록 하려면,

Switch #conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch (config)#errdisable flap-setting cause link-flap max-flaps 10 time 10
Switch (config)#end

Switch #show errdisable flap-values
ErrDisable Reason Flaps Time (sec)
----------------- ------ ----------
pagp-flap 3 30
dtp-flap 3 30
link-flap 10 10

이제, link-flap 값이 변경 된 것을 볼 수 있다.

link-flap 발생한 경우 자동 복구된 로그.

May 30 01:49:23: %LINK-3-UPDOWN: Interface FastEthernet0/39, changed state to down
May 30 07:29:24: %PM-4-ERR_DISABLE: link-flap error detected on Fa0/39, putting Fa0/39 in err-disable state
May 30 07:29:54: %PM-4-ERR_RECOVER: Attempting to recover from link-flap err-disable state on Fa0/39
May 30 07:30:00: %LINK-3-UPDOWN: Interface FastEthernet0/39, changed state to up

참고문서: https://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/69980-errdisable-recovery.html

답글 남기기

Your email address will not be published.