From: ccie2k4@gmail.com
Date: Sun Jul 08 2007 - 01:42:30 ART
How about if you disable SPT for that vlan on one of the switches and than
configure the opposite end for BPDU guard? Would this config be safe from
SPT loops?
On 7/5/07, Gupta, Gopal (NWCC) <gopal.gupta@hp.com> wrote:
>
>
> Hi sadiq,
>
> Yes,
> BPDUs will be sent out the link if the port were an access port between
> the 2 switches, because they will create a spanning tree instance for
> that vlan they are in.
>
> Regds
> Gops
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Sadiq Yakasai
> Sent: Thursday, July 05, 2007 14:23
> 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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