[c-nsp] spanning-tree flaps with BVI routed interface

Kevin Graham mahargk at gmail.com
Sun Mar 18 22:10:40 EST 2007


If its a 4507, I'm guessing you've got at least a SupIV -- why not
flip the 2811 and 5800's uplinks to /30's L3 links and get rid of the
BVI's and L2 considerations?

On 3/16/07, Justin M. Streiner <streiner at cluebyfour.org> wrote:
> On Fri, 16 Mar 2007, Brian wrote:
>
> > Has anyone experienced this before?
>
> I'm assuming one of the 4507s is supposed to be the root bridge for VLAN
> 697?  Is it explicitly as suchon the appropriate 4507?  Also, do trunk
> types (dot1q or ISL), native VLANs, etc match in all of the right places?
>
> jms
>
> > On 3/9/07, Brian <bms314 at gmail.com> wrote:
> >>
> >> I have a 2811 multihomed to two 4507 core routers.  The router is
> >> configured with a BVI to provide redundancy to the core.  However, I
> >> continually see a host flapping message in the core router every 30 seconds.
> >>
> >>
> >> Mar  9 15:18:38 Central: %C4K_EBM-4-HOSTFLAPPING: Host 00:1A:2F:C7:2E:50
> >> in vlan 697 is flapping between port Gi7/31 and port Po27
> >> Mar  9 15:19:08 Central: %C4K_EBM-4-HOSTFLAPPING: Host 00:1A:2F:C7:2E:50
> >> in vlan 697 is flapping between port Gi7/31 and port Po27
> >> Mar  9 15:19:38 Central: %C4K_EBM-4-HOSTFLAPPING: Host 00:1A:2F:C7:2E:50
> >> in vlan 697 is flapping between port Gi7/31 and port Po27
> >>
> >> Gi7/31 is the physical connection on the 1st 4507 and Po27 is the link
> >> between the 4507's.  The 2nd 4507 has similar log messages.
> >>
> >>
> >> The config of the 2811 is as follows:
> >>
> >>
> >> interface FastEthernet0/0
> >>  no ip address
> >>  duplex full
> >>  speed 100
> >>  bridge-group 1
> >>
> >> interface FastEthernet0/1
> >>  no ip address
> >>  duplex full
> >>  speed 100
> >>  bridge-group 1
> >>
> >> interface BVI1
> >>  ip address 204.X.X.X 255.255.255.224
> >>
> >> bridge 1 protocol ieee
> >> bridge 1 route ip
> >>
> >>
> >> I believe spanning-tree should block one of the ports and keep the other
> >> port in a forwarding state.  It seems to be bouncing back and forth.  Any
> >> ideas as to what could be causing this behavior and/or how to correct it?
> >>
> >> Thanks,
> >> Brian
> >>
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> >
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