Flapping Link

[burtsbees]

Just FYI...here's what my log looks like with a bad ethernet cable in my C2924XL switch...

Switch#sh logg
Syslog logging: enabled (0 messages dropped, 0 flushes, 0 overruns)
Console logging: level debugging, 811 messages logged
Monitor logging: level debugging, 0 messages logged
Buffer logging: level debugging, 811 messages logged
File logging: disabled
Trap logging: level debugging, 815 message lines logged
Logging to 10.68.68.3, 815 message lines logged

Log Buffer (4096 bytes):
%LINK-3-UPDOWN: Interface FastEthernet0/15, changed state to down
3d08h: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/15, changed state to down
3d08h: %LINK-3-UPDOWN: Interface FastEthernet0/15, changed state to up
3d08h: %RTD-1-LINK_FLAP: FastEthernet0/15 link down/up 7 times per min
3d08h: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/15, changed state to up
3d08h: %RTD-1-LINK_FLAP: FastEthernet0/15 link down/up 7 times per min
3d08h: %RTD-1-LINK_FLAP: FastEthernet0/15 link down/up 6 times per min
3d08h: %RTD-1-LINK_FLAP: FastEthernet0/15 link down/up 5 times per min
3d08h: %LINK-3-UPDOWN: Interface FastEthernet0/15, changed state to down
3d08h: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/15, changed state to down
3d08h: %LINK-3-UPDOWN: Interface FastEthernet0/15, changed state to up
3d08h: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/15, changed state to up
3d08h: %LINK-3-UPDOWN: Interface FastEthernet0/15, changed state to down
3d08h: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/15, changed state to down
3d08h: %LINK-3-UPDOWN: Interface FastEthernet0/15, changed state to up
3d08h: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/15, changed state to up
3d08h: %LINK-3-UPDOWN: Interface FastEthernet0/15, changed state to down
3d08h: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/15, changed state to down
3d08h: %LINK-3-UPDOWN: Interface FastEthernet0/15, changed state to up
3d08h: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/15, changed state to up
3d08h: %LINK-3-UPDOWN: Interface FastEthernet0/15, changed state to down
3d08h: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/15, changed state to down
3d08h: %LINK-3-UPDOWN: Interface FastEthernet0/15, changed state to up
3d08h: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/15, changed state to up
3d08h: %LINK-3-UPDOWN: Interface FastEthernet0/15, changed state to down
3d08h: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/15, changed state to down
3d08h: %LINK-3-UPDOWN: Interface FastEthernet0/15, changed state to up
3d08h: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/15, changed state to up
3d08h: %LINK-3-UPDOWN: Interface FastEthernet0/15, changed state to down
3d08h: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/15, changed state to down
3d08h: %LINK-3-UPDOWN: Interface FastEthernet0/15, changed state to up
3d08h: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/15, changed state to up
3d08h: %LINK-3-UPDOWN: Interface FastEthernet0/15, changed state to down
3d08h: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/15, changed state to down
3d08h: %LINK-3-UPDOWN: Interface FastEthernet0/15, changed state to up
3d08h: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/15, changed state to up
3d08h: %LINK-3-UPDOWN: Interface FastEthernet0/15, changed state to down
3d08h: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/15, changed state to down
3d08h: %LINK-3-UPDOWN: Interface FastEthernet0/15, changed state to up
3d08h: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/15, changed state to up
3d08h: %LINK-3-UPDOWN: Interface FastEthernet0/15, changed state to down
3d08h: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/15, changed state to down
3d08h: %LINK-3-UPDOWN: Interface FastEthernet0/16, changed state to up
3d08h: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/16, changed state to up
3d08h: %LINK-3-UPDOWN: Interface FastEthernet0/16, changed state to down
3d08h: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/16, changed state to down
3d08h: %LINK-3-UPDOWN: Interface FastEthernet0/17, changed state to down
3d08h: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/17, changed state to down
3d08h: %LINK-3-UPDOWN: Interface FastEthernet0/17, changed state to up
3d08h: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/17, changed state to up
Switch#

Note the
"3d08h: %RTD-1-LINK_FLAP: FastEthernet0/15 link down/up 7 times per min"

Burt

 

[maczen]

Yeah right.. You know you got bored and sat there plugging/unplugging the cable... I bet you go through light bulbs like crazy! LoL

B Haines
CCNA R&S, ETA FOI

 

[burtsbees]

Maybe...in, out, in, out...I like that...what can I say?

Burnt Butt

 

[Belushi]

This is not completely uncommon. Bad cable or bad nic or possibly bad interfaceon your switch could cause this.

 

[burtsbees]

Right---I was just showing this in the Certification forum as an example for all the new people wanting to get certified.

Burt

 

[Cluebird]

The question becomes, "Do flapping links cause my packets to fly?

 

[burtsbees]

And if they do, will they fly upside-down over my newly-washed car? And if not, does that even matter, since I park it in the garage?

Beer

 

[Cluebird]

I park IT in the NOC. Or sometimes MDFs and IDFs. For now, IT is in my workshop/barn.

Another question becomes, "When we find a broken interface, have we discovered the missing link?

 

[burtsbees]

No. The missing link is my older brother. I have already sold him to the Smithsonian for $15,000,000.00
I think I'll spend it on Ebay...

Burt