From: Antonio Soares (amsoares@netcabo.pt)
Date: Wed Jul 04 2007 - 20:55:43 ART
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
This archive was generated by hypermail 2.1.4 : Sat Aug 18 2007 - 08:17:39 ART