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Community Member

Bug or What

greeting all,

i have a trunk connection between 3750 and 4506 and the trunk link is up however data traffic is not going through, i can see that when i ping from 4506 to the 3750 the icmp reach the 3750 but however it is not returning back , is it a BUG?


Re: Bug or What


It could be one of many things.

First it could be a routing issue, ie the packet hits the 3750 but the answer is sent somewhere else if there is a routing problem, or not at all if there is no route to the net and there is no default gateway.


there could be an ACL that does not allow the icmp incomming, or icmp outgoing.

The port could be in span-tree blocking mode

My guess is that it is most likely not a bug but a misconfiguration.


Hall of Fame Super Silver

Re: Bug or What

Hello Seifeddine,

verify the native vlan settings on both sides with

sh interface type x/y switchport

look for native vlan line

look also for the list of vlans permitted on the trunk on both sides.

Hope to help


Community Member

Re: Bug or What

Hi Giusp,

Thanks for your answer , actually i fixed the prob well i was using Dot1q as a trunk and then when i failed to ping i noticed that the i have an encapsulation failure in my switch from the debug ip packet 120 (120 is an ACL that permit the icmp) so it was for sure a failure in the tagging since Dot1q don`t tag the native vlan however when using this command : vlan dot1q tage native everything got fixed

Thanks for your answer.... hey the NetPro forum looks weird i really prefere the old one

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