From: Brian Dennis (bdennis@internetworkexpert.com)
Date: Sun Jan 28 2007 - 01:42:48 ART
Problem:
VLAN 30 is being pruned on CAT1's trunk link to CAT2.
Cause:
One of the switches "behind" CAT2 is pruning the VLAN. CAT3 or CAT4 is
sending the VTP pruning message down the trunk link to CAT2. CAT2 is in
transparent mode so it just passes the message onto CAT1. CAT1 then removes
the VLAN from the trunk to CAT2 and the problem is created.
Solution:
With CAT2 being in VTP transparent mode you need to ensure that CAT3 or CAT4
do not prune VLAN30 on the trunk link to CAT2.
Lastly, I was able to recreate the problem and verify the solution. And yes
I have nothing better to do on a Saturday night ;-)
--Brian Dennis, CCIE4 #2210 (R&S/ISP-Dial/Security/SP) bdennis@internetworkexpert.com Internetwork Expert, Inc. http://www.InternetworkExpert.com Toll Free: 877-224-8987 Direct: 775-745-6404 (Outside the US and Canada)
On 1/27/07 6:59 PM, "Michael Zuo" <mzuo@ixiacom.com> wrote:
> Yes, there are two more, physical connections are as follows: > > > CAT1 f0/14 to CAT2 f0/14 > CAT1 f0/23 to CAT3 f0/23 > CAT1 f0/22 to CAT4 f0/22 > CAT2 f0/22 to CAT3 f0/22 > CAT2 f0/23 to CAT4 f0/23 > CAT3 f0/14 to CAT4 f0/14 > CAT3 f0/15 to CAT4 f0/15 > > > Spanning tree port state as follows: > > CAT1#sh span vlan 30 > > VLAN0030 > Spanning tree enabled protocol ieee > Root ID Priority 32798 > Address 0011.20a9.9280 > This bridge is the root > Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec > > Bridge ID Priority 32798 (priority 32768 sys-id-ext 30) > Address 0011.20a9.9280 > Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec > Aging Time 300 > > Interface Role Sts Cost Prio.Nbr Type > ---------------- ---- --- --------- -------- > -------------------------------- > Fa0/4 Desg FWD 19 128.4 P2p > Fa0/14 Desg FWD 19 128.14 P2p > Fa0/22 Desg FWD 19 128.22 P2p > Fa0/23 Desg FWD 19 128.23 P2p > > CAT1# > > CAT2(config)#do sh span vlan 30 > > VLAN0030 > Spanning tree enabled protocol ieee > Root ID Priority 32798 > Address 0011.20a9.9280 > Cost 19 > Port 14 (FastEthernet0/14) > Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec > > Bridge ID Priority 32798 (priority 32768 sys-id-ext 30) > Address 0011.5c63.0e00 > Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec > Aging Time 300 > > Interface Role Sts Cost Prio.Nbr Type > ---------------- ---- --- --------- -------- > -------------------------------- > Fa0/5 Desg FWD 19 128.5 P2p > Fa0/14 Root FWD 19 128.14 P2p > Fa0/22 Desg FWD 19 128.22 P2p > Fa0/23 Desg FWD 19 128.23 P2p > > CAT2(config)# > > CAT3(config)#do sh span vlan 30 > > VLAN0030 > Spanning tree enabled protocol ieee > Root ID Priority 32798 > Address 0011.20a9.9280 > Cost 19 > Port 23 (GigabitEthernet1/0/23) > Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec > > Bridge ID Priority 32798 (priority 32768 sys-id-ext 30) > Address 0013.c4fc.8280 > Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec > Aging Time 300 > > Interface Role Sts Cost Prio.Nbr Type > ---------------- ---- --- --------- -------- > -------------------------------- > Gi1/0/14 Altn BLK 4 128.14 P2p > Gi1/0/15 Altn BLK 4 128.15 P2p > Gi1/0/22 Altn BLK 19 128.22 P2p > Gi1/0/23 Root FWD 19 128.23 P2p > > CAT3(config)#d > > > > CAT4(config)#do sh span vlan 30 > > VLAN0030 > Spanning tree enabled protocol ieee > Root ID Priority 32798 > Address 0011.20a9.9280 > Cost 19 > Port 22 (GigabitEthernet1/22) > Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec > > Bridge ID Priority 32798 (priority 32768 sys-id-ext 30) > Address 0012.7f34.a7c0 > Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec > Aging Time 300 > > Interface Role Sts Cost Prio.Nbr Type > ---------------- ---- --- --------- -------- > -------------------------------- > Gi1/14 Desg FWD 4 128.14 P2p > Gi1/15 Desg FWD 4 128.15 P2p > Gi1/22 Root FWD 19 128.22 P2p > Gi1/23 Altn BLK 19 128.23 P2p > > CAT4(config)# > > > thanks > > -----Original Message----- > From: Brian Dennis [mailto:bdennis@internetworkexpert.com] > Sent: Saturday, January 27, 2007 6:40 PM > To: Michael Zuo; Alex Ouraev; ccielab@groupstudy.com > Subject: Re: ICMP showing encapsulation failed > > > Are there any other switches in this network that we aren't seeing in > your > diagram?
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