Skip navigation
Cisco Learning Home > CCNP R&S Study Group > Discussions
2516 Views 3 Replies Latest reply: Jul 13, 2010 6:59 PM by Brian RSS

Currently Being Moderated

BCMSN- BPDU Filtering doubt

Jul 13, 2010 9:18 AM

Cristian Silva 6 posts since
Sep 9, 2009

Hello,

       This is my first post in this site. I'm studyng to take the BCMSN 642-812, and i have a doubt of the feature "BPDU Filtering" prevent the interface that are in port-fast to SEND and RECIVE BPDUS???? I search it in cisco.com but it only say that prevent sending bpdu. It doesn't tell anything of reciving them.

 

 

http://www.cisco.com/en/US/docs/switches/lan/catalyst4000/7.4/configuration/guide/stp_enha.html#wp1030035

 

 

ps. I'm sorry for my english

  • Tim 13 posts since
    Mar 22, 2010
    Currently Being Moderated
    1. Jul 13, 2010 9:55 AM (in response to Cristian Silva)
    Re: BCMSN- BPDU Filtering doubt

    BPDU filters both sending and receiving.

     

    note: If a BPDU is received on a Port Fast-enabled  interface, the interface loses its Port Fast-operational status, and  BPDU filtering is disabled.

     

    http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/release/12.2_52_se/configuration/guide/swstpopt.html#wp1046220

     

    Tim

  • Sal 215 posts since
    Nov 23, 2009
    Currently Being Moderated
    2. Jul 13, 2010 12:59 PM (in response to Cristian Silva)
    Re: BCMSN- BPDU Filtering doubt

    Source  CCNP Quick Ref Guide :Chapter 3: Spanning Tree [ 125 ]

    Chapter 3 Spanning Tree [ 125 ].png

  • Brian 2,971 posts since
    Aug 17, 2009
    Currently Being Moderated
    3. Jul 13, 2010 6:59 PM (in response to Cristian Silva)
    Re: BCMSN- BPDU Filtering doubt

    Aloha SherKno,

     

    BPDU filtering works differently depending on how it is configured.  There are actually two ways to enable BPDUFiltering, "globally" and per "interface".

     

    To enter globally, use the following command:

     

    (config)#spanning-tree portfast bpdufilter default

     

    What this command does, is enable bpdufiltering automatically on all ports that have "portfast" enabled.  If portfast is disabled, then BPDU filtering will not be enabled on that port.  In global mode, the port will not send BPDUs, however, if the port receives a BPDU the port losses the portfast feature and behaves normally.  BPDU filtering is now disabled.

     

    To enter per interface, use the following command:

     

    (config-if)#spanning-tree bpdufilter enable

     

    What this command does, is enable bpdufiltering on the port and the port will not send any BPDUs nor will it process any BPDUs it receives.  It basically drops all received BPDUs.

     

    Notice the different configuration modes in the above commands.  Cisco recommends to use this feature with extreme caution, as bridging loops can/may occur.

     

    HTH

Actions

More Like This

  • Retrieving data ...

Bookmarked By (0)