iev4 lab20 802.1q trunking/tunneling problem

From: Ben (bmunyao@gmail.com)
Date: Wed Jun 27 2007 - 02:32:25 ART


Hi Group

This lab calls for the establishment of dot1q trunks and tunnel as depicted
below.

                        dot1q tunnel (EtherChannel)
-----------------------------------------------------------------------------------------
sw3--------------------------------sw4-----------------------------------------sw1
                dot1q trunk | dot1q trunk
                                        |
                                        |dot1q trunk
                                        |
                                        |
                                      sw2

The problem I encountered was the dot1q trunks between sw1-sw4 and sw2-sw4
reporting a "loopback detected" error and going into error-disabled state.
The spanning tree section involved using MST, and I confirmed that STP was
not disabled on any MST instance.
I configured the tunneling interfaces on sw4 as follows:

int f0/13, int f0/19
 sw acc vl 100
 sw trunk encap dot
 sw mode dot1q
 sw nonegotiate
 l2protocol point-to-point lacp
 l2protocol cdp
 l2protocol vtp

int f0/15, int f0/21
 sw acc vl 200
 sw trunk encap dot
 sw mode dot1q
 sw nonegotiate
 l2protocol point-to-point lacp
 l2protocol cdp
 l2protocol vtp

I configured MST on all switches as follows:

spann mode mst
spann mst config
 name IESTP
 ver 10
 instance 1 vlan 1,5,12,107
 instance 2 vlan 27,34,58
 instance 3 vlan 46,89,363

Has anyone else done this lab and seen this problem? I couldn't figure it
out, and would welcome any input on what could have caused it.

Thanks

Ben



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