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DTP link downs



how relevant is “show dtp interface x/x” link down counts in access ports? Is it something to worry about when there is no link down log in buffer.

Thank you


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Any device connected to that port ? can you post the output here to understand, also give us information what device is this and what IOS code running ?



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Thanks BB.

the port is user port connecting to PC. Switch is catalyst 4510. Can’t provide the actual logs at the moment but got below from net. Below has 2 link downs…in my case some ports has more than 100 link downs while the actual port is not down. So when the troubleshooting actual port down, just curious how relevant and why dtp has counts even when it has configured as access port.

  683072 packets received (683072 good)
  0 packets dropped
      0 nonegotiate, 0 bad version, 0 domain mismatches, 
      0 bad TLVs, 0 bad TAS, 0 bad TAT, 0 bad TOT, 0 other
  682938 packets output (682938 good)
      682938 native, 0 software encap isl, 0 isl hardware native
  0 output errors
  0 trunk timeouts
  0 link ups
  2 link downs, last link down on Wed Sep 23 2015, 16:57:01




If this is a user port then user might reload or turned off and on his/her PC.

Then link will go down.

DTP is Cisco proprietary protocol and used to negotiate forming a trunk between two Cisco devices

In this case you don`t need to check it because you have a user connected to it, not a switch.




not sure we understand this, what is the main issue ? DTP on end point device where connected ?



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Thanks Ventsi & BB.

concern is link down counts in user switch port connected to user PC. Show dtp interface x/x has 100s of link down while the port is not physically down. User access port should not be sending dtp, curious what causes this count to go up in switch ports.

thank you 

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