From: Sadiq Yakasai (sadiqtanko@gmail.com)
Date: Thu Jul 05 2007 - 05:53:11 ART
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
> > 00000000018001000F905F5B00000000008001000F905F5B0080190000140002000F00
> > 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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