3550-3750 Not trunking

Mar 22, 2006 3 Replies
3550-3750 Not trunking open original image

Trunking on two switches: 3550 and 3750; 3all 550 vtp counters all zero; any ideas what's wrong here ? TIA,Ned


3550 vtp mode transparent vtp domain TEST1 ! interface GigabitEthernet1/0/49 switchport trunk encapsulation dot1q switchport mode trunk ! Cat3550#
6d03h: %SYS-5-CONFIG_I: Configured from console by consoleshow int g0/1 trunk Port Mode Encapsulation Status Native vlan Gi0/1 on 802.1q trunking 1 Port Vlans allowed on trunk Gi0/1 1-4094 Port Vlans allowed and active in management domain Gi0/1 1,18,21,172 Port Vlans in spanning tree forwarding state and not pruned Gi0/1 1,18,21,172 Cat3550#show vtp count VTP statistics: Summary advertisements received : 0 Subset advertisements received : 0 Request advertisements received : 0 Summary advertisements transmitted : 0 Subset advertisements transmitted : 0 Request advertisements transmitted : 0 Number of config revision errors : 0 Number of config digest errors : 0 Number of V1 summary errors : 0 VTP pruning statistics: Trunk Join Transmitted Join Received Summary advts received from non-pruning-capable device

---------------- ---------------- ----------------



--------------------------- Gi0/1 0 0 0



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3750 vtp domain TEST1 vtp mode transparent interface GigabitEthernet0/1 switchport trunk encapsulation dot1q switchport mode trunk no ip address



3750#show vtp count VTP statistics: Summary advertisements received : 1137 Subset advertisements received : 1 Request advertisements received : 0 Summary advertisements transmitted : 1085 Subset advertisements transmitted : 2 Request advertisements transmitted : 1 Number of config revision errors : 0 Number of config digest errors : 0 Number of V1 summary errors : 0 VTP pruning statistics: Trunk Join Transmitted Join Received Summary advts received from non-pruning-capable device

---------------- ---------------- ----------------



--------------------------- Gi1/0/49 0 0 0



3750#show int g1/0/49 trunk Port Mode Encapsulation Status Native vlan Gi1/0/49 on 802.1q trunking 1 Port Vlans allowed on trunk Gi1/0/49 1-4094 Port Vlans allowed and active in management domain Gi1/0/49 1-2,21,96-97,172,921,926 Port Vlans in spanning tree forwarding state and not pruned Gi1/0/49 1-2,21,96-97,172,921,926
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You have VTP turned off... VTP transparent, means to ignore VTP packets and to pass them from one trunk port to all other trunk ports as if they were broadcast packets. VTP disabled, the switch also ignores VTP packets but does not propagated out to other trunk ports. Setting the VTP domain has no effect when VTP is disabled or in transparent mode. The 3570 must count the packets even though VTP is not turned on.

Scott

You need to turn off auto neg on both sides or make one side auto and the other hardcode

configure "switchport mode dynamic desirable" on both side as per Cisco best practices.

(Personally I use mode on )

show trunk

For Cisco recommended trunk mode settings, refer to the "Dynamic Trunking Protocol" section of "Best Practices for Catalyst 6500/6000 Series and Catalyst 4500/4000 Series Switches Running Cisco IOS Software"

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