From: Gary Duncanson (gary.duncanson@googlemail.com)
Date: Thu Jul 05 2007 - 09:26:35 ART
A switch experiencing a change in STP topology sends a TCN BPDU out it's
root port, repeating it every hello time until it is acknowledged by the DP
on that segment so yes.
----- Original Message -----
From: "Salau, Yemi" <yemi.salau@siemens.com>
To: "Antonio Soares" <amsoares@netcabo.pt>; "Sadiq Yakasai"
<sadiqtanko@gmail.com>; <ccie2k4@gmail.com>
Cc: "Cisco certification" <ccielab@groupstudy.com>
Sent: Thursday, July 05, 2007 11:47 AM
Subject: RE: BPDUGuard - interconnecting 2 switches
> Hello Guys,
>
> Is is valid that only Designated ports that send BPDUs? I always thought
> Root Ports do as well
>
> Many Thanks
>
> Yemi Salau
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Antonio Soares
> Sent: Thursday, July 05, 2007 11:21 AM
> To: 'Sadiq Yakasai'; ccie2k4@gmail.com
> Cc: 'Cisco certification'
> Subject: RE: BPDUGuard - interconnecting 2 switches
>
> In the example i gave, the connection is not a trunk. So we will have
> BPDU's
> only in the access VLAN. In that segment, one port will be designated
> and
> the other will be a root port. Only the designated port send BPDU's so
> we
> must take this into account when enabling those BPDU filtering options:
>
> 1) (config-if)# spanning-tree bpdufilter enable
>
> Never sends or receives BPDUs.
>
> 2) (config-if)# spanning-tree bpduguard enable
>
> If a BPDU is received, the Port is put in the errDisable state.
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Sadiq Yakasai
> Sent: quinta-feira, 5 de Julho de 2007 9:53
> To: ccie2k4@gmail.com
> Cc: Cisco certification
> Subject: Re: BPDUGuard - interconnecting 2 switches
>
> hey guys,
>
> i have been thinking about this subject actually and thot,
>
> Do BPDU's get sent out a normal access port? I thot the whole idea BPDU
> Guard/Filter only affects incoming BPDU's and not outgoing in the first
> place.
>
> Antonio,
>
> The link between SW1 and SW2 is a trunk link isnt it? Would BPDU's get
> sent
> out the link if the port were an access port between the 2 switches?
>
>
>
> On 7/5/07, ccie2k4@gmail.com <ccie2k4@gmail.com> wrote:
>> Hi Antonio,
>>
>> Thanks for replying. In the case I was using the port would be a L2
>> port however it would be an access port. So I was trying to find out
>> what would be the problem if I configured an L2 port as an access port
>
>> going to another switch which would have an SVI interface and that
>> would be the default gateway for any devices attached to the L2
>> switch. Would that port still send out BPDU's and if so would that
> cause a
> loop if there is redundancy?
>>
>> On 7/4/07, Antonio Soares <amsoares@netcabo.pt> wrote:
>> >
>> > BPDU's are sent by L2 designated ports. A L3 port does not run STP
>> > unless you attach to it a bridge-group.
>> >
>> > +++++++++++++++++++++++++++++++++++++++++++++++++
>> > SW1 is receiving BPDU's on its Root Port from SW2
>> > +++++++++++++++++++++++++++++++++++++++++++++++++
>> > SW1#
>> > 01:48:37: STP: VLAN0001 rx BPDU: config protocol = ieee, packet from
>> > GigabitEthernet0/23 , linktype IEEE_SPANNING , enctype 2, encsize
>> > 17
>> > 01:48:37: STP: enc 01 80 C2 00 00 00 00 0F 90 5F 5B 19 00 26 42 42
>> > 03
>> > 01:48:37: STP: Data
>> > 00000000018001000F905F5B00000000008001000F905F5B0080190000140002000F
>> > 00
>> > 01:48:37: STP: VLAN0001 Gi0/23:0000 00 00 01 8001000F905F5B00
>> > 00000000 8001000F905F5B00 8019 0000 1400 0200 0F00
>> > 01:48:37: STP(1) port Gi0/23 supersedes 0 SW1#
>> > +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>> > As soon as i configured SW2 port as L3, BPDU's are not received
>> > +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>> > 01:48:39: %LINEPROTO-5-UPDOWN: Line protocol on Interface
>> > GigabitEthernet0/23, changed state to down
>> > 01:48:40: %LINK-3-UPDOWN: Interface GigabitEthernet0/23, changed
>> > state to down SW1#
>> > 01:48:42: %LINK-3-UPDOWN: Interface GigabitEthernet0/23, changed
>> > state to up
>> > 01:48:43: %LINEPROTO-5-UPDOWN: Line protocol on Interface
>> > GigabitEthernet0/23, changed state to up SW1#
>> >
>> >
>> >
>> > -----Original Message-----
>> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of
>> > ccie2k4@gmail.com
>> > Sent: quarta-feira, 4 de Julho de 2007 23:16
>> > To: Cisco certification
>> > Subject: BPDUGuard - interconnecting 2 switches
>> >
>> > Hi Folks,
>> >
>> > Just trying to get an idea of how SPT and BPDU guard would affect
> this
>> > scenario. Say I have 2 * 3550 switches and I am using one as a pure
> L2
>> > switch while the other one is being used as a router.
>> >
>> > Can I connect them without using a trunk? What I mean is can I make
> that
>> > port that interconnect's the 2 devices an access port with portfast
>> > configured and than use a SVI interface on that router as the
> default
>> > gateway? I have done this and it works without issues as far as I
> know
>> > however just thinking about it now I am wondering why it doesn't
> cause
> any
>> > problems. When you make a port an access port it usually is to
> connect
> end
>> > devices like pc's etc however in this case the other device is also
> a
>> > switch
>> > and that port on that device will also be an access port in a vlan.
> I
> tend
>> > to think that it would send out BPDU's and if the other end has
> BPDUguard
>> > configured than it would disable the port wouldn't it?
>> >
>> > Does the device acting as a router still send out a BPDU on that
> port?
>> >
>> > I would like to make the L2 switch the root of the spanning tree
> hence
>> > just
>> > want to confirm if I have BPDU guard configured on that port will be
> a
>> > problem.
>> >
>> > When does a switch send out a BPDU? I mean I have read all about how
> when
>> > there is a topology change or during root election etc but say for
>> > instance
>> > in this scenario if I didn't have any spanning-tree on the 3550
> being
> used
>> > as a router would it still send out a BPDU?
>> >
>> > Thx
>> >
>> >
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