Hey there guys !
I’ve been playing with some STP features like BPDUGuard and BPDUfilter and I configured my routers to “act” like switches . I wanted the routers to send BPDU and then the switch to put the port in errdisable state.
I configured the router this way:
bridge 1 protocol ieee
bridge 1 hello 1
interface fa0/1
bridge-group 1
my switch is configured with either bpduguard globally or per interface (I tested both)
My concern is not about the switch … it’s more about the routers ….
The only way for me to send some BPDU from the routers is to do a shut / no shut on the interface , then the router sends a BPDU and the switch put the port in errdisable ….
After some time , the router stop sending BPDU …
Rack1R5#sh clock
*21:53:18.659 UTC Tue Jan 18 2011
Rack1R5#sh spanning int fa0/1
Port 4 (FastEthernet0/1) of Bridge group 1 is forwarding
Port path cost 19, Port priority 128, Port Identifier 128.4.
Designated root has priority 5, address 001a.a240.b600
Designated bridge has priority 49157, address 000f.233a.8180
Designated port id is 128.5, designated path cost 3019
Timers: message age 3, forward delay 0, hold 0
Number of transitions to forwarding state: 5
BPDU: sent 33, received 177
Rack1R5#
Rack1R5#sh run | sec bridge
bridge-group 1
bridge 1 hello-time 1
bridge 1 protocol ieee
Rack1R5#
Rack1R5#sh clock
*21:55:32.103 UTC Tue Jan 18 2011
Rack1R5#sh spanning int fa0/1
Port 4 (FastEthernet0/1) of Bridge group 1 is forwarding
Port path cost 19, Port priority 128, Port Identifier 128.4.
Designated root has priority 5, address 001a.a240.b600
Designated bridge has priority 49157, address 000f.233a.8180
Designated port id is 128.5, designated path cost 3019
Timers: message age 3, forward delay 0, hold 0
Number of transitions to forwarding state: 5
BPDU: sent 33, received 220
Edit:
Ok with the help of one of my friend I know what I did wrong ……
In fact the router is running 802.1D and as you know, only the rootbridge sends BPDU.
So when the interface comes up, the router sends a BPDU and receive a BPDU from the Rootbridge via the Switch. Then the election occurs and the router realize that he is not the root bridge so he ******* and keep listening to the received BPDU.
Once there is a Topology Change , the router can send the BPDU to claim “IM THE ROOT !” and if it receives a better (inferior) BPDU , the cycle starts again
AccessServer#7
[Resuming connection 7 to sw1 ... ]
Rack1SW1(config)#int fa0/1
Rack1SW1(config-if)#spanning bpdufilter disab
Rack1SW1(config-if)#
AccessServer#1
[Resuming connection 1 to R1 ... ]
Rack1R1#sh clock
*05:12:51.848 UTC Fri Mar 1 2002
Rack1R1#sh spanning int fa0/0
Port 4 (FastEthernet0/0) of Bridge group 1 is forwarding
Port path cost 19, Port priority 128, Port Identifier 128.4.
Designated root has priority 146, address 001a.a240.b600
Designated bridge has priority 146, address 001a.a240.b600
Designated port id is 128.3, designated path cost 0
Timers: message age 1, forward delay 0, hold 0
Number of transitions to forwarding state: 3
BPDU: sent 187, received 29
Rack1R1#show clock
*05:13:56.594 UTC Fri Mar 1 2002
Rack1R1#sh spanning int fa0/0
Port 4 (FastEthernet0/0) of Bridge group 1 is forwarding
Port path cost 19, Port priority 128, Port Identifier 128.4.
Designated root has priority 146, address 001a.a240.b600
Designated bridge has priority 146, address 001a.a240.b600
Designated port id is 128.3, designated path cost 0
Timers: message age 1, forward delay 0, hold 0
Number of transitions to forwarding state: 3
BPDU: sent 187, received 50
Rack1R1#
Rack1R1#
AccessServer#7
[Resuming connection 7 to sw1 ... ]
Rack1SW1(config-if)#
Rack1SW1(config-if)#spanning bpdufil en
Rack1SW1(config-if)#
AccessServer#1
[Resuming connection 1 to R1 ... ]
Rack1R1#sh clock
*05:14:27.713 UTC Fri Mar 1 2002
Rack1R1#sh spanning int fa0/0
Port 4 (FastEthernet0/0) of Bridge group 1 is forwarding
Port path cost 19, Port priority 128, Port Identifier 128.4.
Designated root has priority 32768, address 0011.20d2.5fe0
Designated bridge has priority 32768, address 0011.20d2.5fe0
Designated port id is 128.4, designated path cost 0
Timers: message age 0, forward delay 0, hold 0
Number of transitions to forwarding state: 3
BPDU: sent 191, received 56
Rack1R1#sh clock
*05:14:47.670 UTC Fri Mar 1 2002
Rack1R1#sh spanning int fa0/0
Port 4 (FastEthernet0/0) of Bridge group 1 is forwarding
Port path cost 19, Port priority 128, Port Identifier 128.4.
Designated root has priority 32768, address 0011.20d2.5fe0
Designated bridge has priority 32768, address 0011.20d2.5fe0
Designated port id is 128.4, designated path cost 0
Timers: message age 0, forward delay 0, hold 0
Number of transitions to forwarding state: 3
BPDU: sent 198, received 56