4507 sho run not showing correct information

[tcorbett]

                   Looking at the following output (show interface status) from one of our 4507s I see gig interfaces 3/2 to 3/6 are all trunked (dot1q). When I look at a show run they do not show as trunked. They should indicate switchport trunk encapsulation dot1q and switchport mode trunk (as does interface gig4/2). I have seven other 4507s all running the same IOS: 12.2(25)EWA8 and they all show the same information in show run and show interface status (as far as trunked goes). This is not a problem as I know the interfaces are trunked and working properly I am just puzzled as to why I see this difference.

Here is the sho int gig3/2 trunk. It looks like you are correct. I did not realize some were set to trunk mode on and others were not. I would think the running config would still show the port using dot1q but I guess not. Thank you for your help! At least now I understand why I see a difference.

Tom

[John Blakley]

My first thought is that the port is left in the default state of "dynamic desirable". This will form a trunk if the other end is either listening for a trunk to be created (dynamic auto) or also wanting to create a trunk (dynamic desirable). The switchport won't show anything under the running config because the default settings haven't been changed for the port. You can also do a "show int g3/2 trunk" to see this.

Can you post the "show int g3/2"?

Your g4/2 has been configured manually to be in trunk mode for dot1q encapsulation.

HTH,

John

[John Blakley · Accepted solution]

Port        Mode         Encapsulation  Status        Native vlan

Gi3/2       auto         n-802.1q       trunking      1

The n-802.1q under encapsulation means that it was "negotiated" to become a trunk. This is normal.

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[tcorbett]

Yes. I see what you are saying. Everything is normal and now it makes sense!

Thanks again for your help!

Tom