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Syslog/flapping question....

Two questions)

1) If someone reset a pc or cable modem will that cause the circuit to flap (as shown below)?

054396: Oct 21 19:51:24.288 PDT: %LINK-3-UPDOWN: Interface FastEthernet0/25, changed state to down

054397: Oct 21 19:51:25.289 PDT: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/25, changed state to down 054398: Oct 22 04:11:50.740 PDT: %LINK-3-UPDOWN: Interface FastEthernet0/25, changed state to up 054399: Oct 22 04:11:51.776 PDT: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/25, changed state to up 054400: Oct 22 04:12:29.280 PDT: %LINK-3-UPDOWN: Interface FastEthernet0/25, changed state to down 054401: Oct 22 04:12:30.308 PDT: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/25, changed state to down

2) Does this mean someone plugged a loopback adaptor into a switch port?

020561: Oct 20 02:21:12.212 PDT: %LINK-3-UPDOWN: Interface FastEthernet0/12, changed state to up 020562: Oct 20 02:21:14.004 PDT: %ETHCNTR-3-LOOP_BACK_DETECTED: Keepalive packet loop-back detected on FastEthernet0/12. 020563: Oct 20 02:21:14.004 PDT: %PM-4-ERR_DISABLE: loopback error detected on Fa0/12, putting Fa0/12 in err-disable state 020564: Oct 20 02:21:16.048 PDT: %LINK-3-UPDOWN: Interface FastEthernet0/12, changed state to down
Reply to
uubozou1
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Yes, depending on the type of PC (e.g. a Mac or some Linux box etc.) you will see the interface going up and down several times. But at the end the last message should indicate that the interface is up.

I don't know.

Regards, Christoph Gartmann

Reply to
Christoph Gartmann

snipped-for-privacy@nonsense.immunbio.mpg.de (Christoph Gartmann) wrote in news:ffl1g1$7o5$ snipped-for-privacy@news.belwue.de:

What type of switch and version is it? Looks very much like a 2950 running pre 12.1.13 switch code. At any rate, you can squelch the link up/downs by putting "no logging event link status" on the interface. You'll still see the err-disables messages and the controller messages. If the err-disable is a problem, you can turn off the condition with "no errdisable detect cause loopback" in global config. We had this happen a lot a long time ago, and it was typically someone with a hub on the port (lots of collisions) or some other type of media converter.

I mention the switch code because in 12.1.13 of the 2950 code, they rewrote the phy drivers. The phy drivers in the previous versions had numerous posted bugs.

hope this helps,

chris

Reply to
Chris Marva

I do not know the answer to this question but I will propose it for discussion to this problem.

020561: Oct 20 02:21:12.212 PDT: %LINK-3-UPDOWN: Interface FastEthernet0/12, changed state to up 020562: Oct 20 02:21:14.004 PDT: %ETHCNTR-3-LOOP_BACK_DETECTED: Keepalive packet loop-back detected on FastEthernet0/12. 020563: Oct 20 02:21:14.004 PDT: %PM-4-ERR_DISABLE: loopback error detected on Fa0/12, putting Fa0/12 in err-disable state 020564: Oct 20 02:21:16.048 PDT: %LINK-3-UPDOWN: Interface FastEthernet0/12, changed state to down

- What happens when you plug a hub into this switchport when the hub has a cable from one port plugged back into itself on another port? - What protects a switch from a non-spanning-tree switch or a hub that already has a loop within it that would consume the overall ethernet bandwidth of this broadcast domain?

Spanning-tree portfast BPDUguard will block ethernet ports when an ethernet switch is connected and BPDUs are received. This would not be the case with a hub.

Reply to
Scott Perry

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