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New Member

stp (ieee802.1d-1998) tcn_bpdu problem?

i use the topology for test stp tcn_bpdu:

sw_1 (root bridge)

|

|<port1:root port>

sw_2

|<port2:designated port>

|

--------pc

sw_2's port1 is root port.

sw_2's port2 is designated port.

0.after the stp tree stable(sw_1 is root bridge),i beging sniffer the port1's ingress&egress package.

1.1min later,i unplug port2.

2.after another 1min,i plug port2.

3.after 3min,i stop sniffer.

from the sniffer file,i fond port1 does't send tcn_bpdu

when i unpluge port2,but it send tcn_bpdu when i pluge

port2.

who can tell me why sw_2 does't send tcn_bpdu when it fond

the port2 down?does it no a topology change?

thans a lots!

1 REPLY
New Member

Re: stp (ieee802.1d-1998) tcn_bpdu problem?

The switch will not send topology change notification bpdu's when sw_2 port2 goes down becaucse that port is in a blocked state. Only forwarding state ports cause topology changes. So a loss in connectivity on port 2 sw2 is not considered a topology change. Please refer to the following links for more detailed information:

http://www.cisco.com/warp/public/473/146.html

http://www.cisco.com/warp/public/473/17.html

If this helps please rate my post, thanks.

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