That's odd because the bpdufilter command is the equivalent to disabling
spanning tree on the interface on which you enable it
From: [email protected]
[mailto:[email protected]] On Behalf Of Michael Lipsey
Sent: Wednesday, March 10, 2010 11:35 PM
To: [email protected]
Subject: [OSL | CCIE_RS] BPDUfilter
So, I'm comparing the differences to BPDUGuard and BPDUFilter.
Guard's fairly easy - if you hear a BPDU you go into err-disable.
Filter however I'm seeing a discrepancy between operation and documentation. If
you check out the link here:
http://www.cisco.com/en/US/partner/docs/switches/lan/catalyst3560/software/release/12.2_46_se/configuration/guide/swstpopt.html#wp1032048
This text on BPDUFilter:
Enabling BPDU Filtering
When you globally enable BPDU filtering on Port Fast-enabled interfaces, it
prevents interfaces that are in a Port Fast-operational state from sending or
receiving BPDUs. The interfaces still send a few BPDUs at link-up before the
switch begins to filter outbound BPDUs. You should globally enable BPDU
filtering on a switch so that hosts connected to these interfaces do not
receive BPDUs. If a BPDU is received on a Port Fast-enabled interface, the
interface loses its Port Fast-operational status, and BPDU filtering is
disabled.
It says that if a bpdu is heard on a filter configured ported - it will lose
its port fast enabled status and filtering will be disabled. I took a trunk
port that was in blocking on one of my switches and configured it as a portfast
port with filtering enabled so of course it received BPDUs from the switch on
the other side but what the text said would happen did not and of course the
port did not go into err-disable:
SW2(config-if)#do sho spannin int f0/19 det
Port 16 (FastEthernet0/19) of VLAN0001 is designated forwarding
Port path cost 3019, Port priority 128, Port Identifier 128.16.
Designated root has priority 32769, address 001b.d490.7980
Designated bridge has priority 49153, address 001a.a256.7780
Designated port id is 128.16, designated path cost 3019
Timers: message age 0, forward delay 0, hold 0
Number of transitions to forwarding state: 1
Link type is point-to-point by default
Bpdu filter is enabled
BPDU: sent 1, received 153
What's the deal here?
Thanks guys!
-Mike
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