Using a Cisco Catalyst 2960-24TC. Port 11 is connected to a data archiving device (10Base-T, custom interface, no manual) used to record all network traffic, then broadcast that data during playback. The archiver records, but upon playback 1 or 2 UDP mesages are broadcast before the port is error disabled. Network Assistant logs the following:
Severity Timestamp Event Description
3-Error Oct 31 21:32:02 Interface GigabitEthernet0/11 - changed state to down
5-Notification Oct 31 21:32:01 Line protocol on Interface GigabitEthernet0/11 - changed state to down
3-Error Oct 31 21:32:00 Loop-back detected on GigabitEthernet0/11.
4-Warning Oct 31 21:32:00 loopback error detected on Gi0/11 putting Gi0/11 in err-disable state
7-Debugging Oct 31 21:31:55 Received 802.1Q BPDU on non trunk GigabitEthernet0/11 VLAN1.
7-Debugging Oct 31 21:31:55 Blocking GigabitEthernet0/11 on VLAN0001. Inconsistent port type.
the log clearly tells that an Loop has been formed, possibile reasons that 2 connections might have been given to the same switch which caused a loop on the network, to avoid this, cisco switches will disable the port("error disabled")automatically for avoiding loop on the entire network.
switch A -----> switch B
switch A -----> switch C
switch A -----> switch D
switch A -----> switch B
YES ofcourse, you can connect the cable twice by doing etherchanneling, without that configuration a loop might form on the network, to avoid this loop, cisco makes the port disable.
what you do is, if all of your switches are Cisco, then what you can do is, juz type "show cdp neighbhours" so that you can easily find out whether the same switch is connected twice. if you find, juz remove 1 cable.
hope this helps.
rate this post if cleared, if not please lemme know about that.
This is actually a pretty cool feature, i didn't even know it existed until I was looking for a solution to advertise a subnet (prefix in BGP talk), only if a certain condition existed. This is exactly what conditional advertisements does
j ai une question j ai achete un routeur cisco 887VA-k9 , je le configuré avec la configuration ci- dessous
si je le lier avec mon pc portable sur l un de ses ports directement ça marche toute est bien ( la connexion internet + m...
Attached policy provides CLI access to the Cisco 4G router over text messaging. Two files are in the attached .tar file:
2. PDF with instructions on how to load and use the .tcl file.