Trunk failure

[nawas]

I have configured a trunk link that goes from my 4006 to a 2950-14 which in trun connects to a 7200 and then to the WAN connection to my vendor. I'm allowing two vlan and have trunk link configured between 4006 and 2950. what I see that trunk link is flapping between the two, it goes down for 3 sec and then come back up, it happens several time almost every hour. First I thought it was a bad cable or port, I changed port and cable but still see the same issue. Can anyone help? here is my configuration:

clear trunk 3/7 1-100,102-107,109-1005

set trunk 3/7 nonegotiate dot1q 101,108,1025-4094

Following are the errors:

2005 Oct 28 11:42:07 %DTP-5-NONTRUNKPORTON:Port 3/7 has become non-trunk

2005 Oct 28 11:42:09 %DTP-5-TRUNKPORTON:Port 3/7 has become dot1q trunk

2005 Oct 28 12:40:06 %DTP-5-NONTRUNKPORTON:Port 3/7 has become non-trunk

2005 Oct 28 12:40:09 %DTP-5-TRUNKPORTON:Port 3/7 has become dot1q trunk

2005 Oct 28 12:40:27 %DTP-5-NONTRUNKPORTON:Port 3/7 has become non-trunk

2005 Oct 28 12:40:31 %DTP-5-TRUNKPORTON:Port 3/7 has become dot1q trunk

[Georg Pauwen]

Hello,

if port 3/7 is supposed to be a trunk port, you might want to manually configure it as such, and also turn off DTP:

switchport mode trunk

switchport trunk encapsulation dot1q/isl

--> manually sets the port as a trunk

switchport nonegotiate

--> turns off DTP

HTH,

GP

[glen.grant]

I would make sure your ports are hardcoded on both ends for speed and duplex, check to see if you are getting errors on either end . Looks like you are already trying to force it on , you could always set one as desirable and the other end as auto and see what happens . Make sure native vlan is the same on both ends.