3750 vs 4507 : Trunking behavior not the same?

demem-cco · ‎11-18-2010

Hi,

I've seen a weird behavior (that I believe shouldn't be!) in trying to connect servers on different type switches.

I'm just trying to figure out why I have this behavior.

#1- We have a server with 2 NICs in teaming, and on the server side they are set in TRUNKING mode....

These links are connected to a 4507 on which the corresponding port is in ACCESS MODE....

And yet....these connections worked !

I tought they shouldn't work, the server side trunks encapsulating packets with 802.1q frame tags, and the switch side not being equipped to decapsulte them...but this did work on the 4507! (if you have an answer to explain this, feel free to elaborate as to why!)

However....

#2- We tried the same setup on a 3750 stack of 4 switches (replaces a 4507 we once had there!)... AND....It doesn't work!

The links don't come up....And the teaming between the NICs doesn't work!

MY QUESTION IS THIS:

Is there a difference in the 802.1Q management from the 4507 standpoint (which seems to know what to do when the server side is in TRUNK mode, but the 4507 side is in ACCESS mode!)

......AND....

The 3750 standpoint (which DOESN'T seem to know what to make of an ACCESS mode on the 3750 port, connected to a TRUNK linked server!)???

IOS on 3750 is c3750-ipservicesk9-mz.122-50.SE3.bin

IOS on 4507 is cat4500-entservicesk9-mz.122-50.SG.bin

I need the feedback.

Thanx,

Droidcrasher

rtjensen4 · ‎11-18-2010

Was the server sending traffic on multipl VLANs or just one? I would guess that the reason it was working was that the native VLAN was being used. In 802.1Q, the native VLAN doesn't get any additional tags. A trunk interface could connect to an access port and pass frames on the native VLAN without having any problems. Was the access-port on the 3750 in the same VLAN as the 4507 was?

demem-cco · ‎11-18-2010

Re: 3750 vs 4507 : Trunking behavior not the same?

Was the server sending traffic on multipl VLANs or just one? I would guess that the reason it was working was that the native VLAN was being used. In 802.1Q, the native VLAN doesn't get any additional tags. A trunk interface could connect to an access port and pass frames on the native VLAN without having any problems. Was the access-port on the 3750 in the same VLAN as the 4507 was?

Thanx for your prompt answer.

To answer you...

The trunked server had 2 active vlans, but only one shooting traffic.

But THAT traffic was NOT from the native vlan and for the record...the native vlan IS the same on both the 4507 and the 3750 stack.

The 4507 passes that traffic...And the 3750...Nope!

And NO...There are no "vlan dot1q tag native" on the 3750 ...No more then on the 4507.

So that's why I'm a bit puzzled! :-)

Anyone!???? ;-D

droidcrasher

glen.grant · ‎11-18-2010

Can you post the configs from the ports ?