From: Hobbs (deadheadblues@gmail.com)
Date: Sun Nov 30 2008 - 02:43:35 ARST
I noticed something strange while playing around with this lab. Cat1 and
Cat4 both think they are root for the vlans 12, 40 and 240. I even loaded
the ipexpert final configs and the issue still exists.
Cat1#show spanning-tree vlan 12 | inc root
This bridge is the root
Cat1#show spanning-tree vlan 40 | inc root
This bridge is the root
Cat1#show spanning-tree vlan 240 | inc root
This bridge is the root
Cat4#show spanning-tree vlan 12 | inc root
This bridge is the root
Cat4#show spanning-tree vlan 40 | inc root
This bridge is the root
Cat4#show spanning-tree vlan 240 | inc root
This bridge is the root
Now Cat1 and Cat4 don't have any trunks directly connected (due to
tunneling) so I am guessing somewhere along the line BPDUs are not getting
tunneled. Cat3 is "between" Cat1 and Cat4 and it shows Cat4 as root (through
Po34).
Cat3#show spanning-tree vlan 12 root | inc VL
VLAN0012 32780 0019.2f02.e980 9 2 20 15
Po34
Cat3#show spanning-tree vlan 40 root | inc VL
VLAN0040 32808 0019.2f02.e980 9 2 20 15
Po34
Cat3#show spanning-tree vlan 240 root | inc VL
VLAN0240 33008 0019.2f02.e980 9 2 20 15
Po34
It looks like Cat3 is not hearing any of Cat1's BPDUs. Otherwise it would
pick Cat1 as root because Cat1 has a lower mac address. Haven't been able to
completely sort this one out but here is one more note:
-If I disable f0/19 on cat1 and cat3, BPDUs flow over the next link in the
bundle (f0/21) and cat4 and cat3 see cat1 as root (rightly so since cat1 has
lower mac). So it looks like the tunnel from cat3 to cat4 is working right,
but not the one from cat1 to cat3.
My session is just about over for this one, but any comments or thoughts for
next time will be greatly appreciated.
thanks!
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