Re: STP loop guard

But like is this the scenario in which u use loopguard...

try something like this
ROOTSW1(fa0/0)----->Sw2----->Sw3----ROOTSW1(fa0/1)

now.! u enable loopguard on Sw3 and Sw2 to prvent looping.! because in
case of a Unidirectional link. both the ports in default config will
transition to forwarding and causing a loop.! so u have loopguard to
prevent that.
Thanking You

Yours Sincerely

Divin Mathew John
divinjohn_at_gmail.com
divin_at_dide3d.com
http://www.dide3d.com
+91 9945430983
+91 9846697191
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PGP PUBLIC KEY BLOCK @ http://www.dide3d.com/divin_Public_PGP_key.txt
Sent from Bangalore, KA, India

2009/4/17 nowy1981 <freemaxis_at_gmail.com>:
> Im a little bit confused of this command, could you clarify it for me:
>
> Cisco CG says:
> "to prevent alternate or root ports from becoming designated ports because
> of a failure that leads to a unidirectional link."
>
> But for example in Adv Tech WB 5.0 I've found:
> "if one of these blocking links transitions to forwarding state erroneously,
> a loop can occur (...) loop guard prevents this by transitioning blocking
> ports into loop-inconsistent istead of rorwarding if BPDUs topp being
> recived from the designated port."
>
> Let's look at the following example.
>
> We have 2 switches and one link between them, SW1 is the root, SW1 fa0/1 is
> DP, SW2 fa0/1 is RP, if unidirectional link exist for example SW2 will not
> able to receive BPDUs from SW1 it put this interface as DP after 30 sec (by
> default).
> If we use spanning-tree guard loop under SW2 fa0/2 interface will be
> blocked.
>
>
> (Tx) ------X------ (Rx)
> ROOT SW1 SW2
> (fa0/1 - Designated Port) (fa0/1-Root Port)
> (Rx) ------------- (Tx)
>
>
> Am I right?
> Can you confirm if I can use it also on interfaces that are in blocking
> state also like IE says?
> Please let me know if I put this command on the right switch.
>
> Thanks in advance!
>
>
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Received on Sat Apr 18 2009 - 00:30:37 ART