Issue with VLANs & Trunk with 2801, Cat 500 & Cat 3524

Unanswered Question
Dec 3rd, 2007


I'm trying to create a trunk link with my Cat Express 500 and Cat 3524 with the 2801 routing for all vlans.

I currently have 2 VLANs for data and voice for my production environment on the 500 switch and everything works fine.

I added a sperate VLAN on the 500 for LAB stuff. I needed the 3524 for expansion of my LAB and have the ability to do PoE.

I got everything configured the way I think it should work - I plug the 3524 into its trunk port on the 500 and it goes thru the Blocking, Listening, Forwarding, ect, of Spanning Tree - then when the port goes active everything seems to be working fine.

But its not. I can ping from every VLAN to the router and between VLANS (where is allowed) but I cannot get to the internet. Not from workstations on any vlan - or from the router CLI itself.

And when I unplug the 3524 from the 500 everything, including the internet, starts working again.

Let me know if any of you have any idea's as to what is going on - I am fresh out of idea's.


I have this problem too.
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Edison Ortiz Mon, 12/03/2007 - 18:00

I'm assuming the 2801 is providing the internet access with NAT.

Is the 2801 connected to the 3524 ?

Can you ping the 2801 private interface while the 500 and 3524 switches are trunking ?

Is your IP address the same while the trunking configuration is working or not ?

If you can, post the config from the 3 devices.

jdcrowder Mon, 12/03/2007 - 18:40

Yes it is using NAT.

No, it is connected to the 500

Yes I can ping the private interface while the 500 and the 3524 are trunking.

Yes, all IP addresses are the same while the switches are trunking.

I'll get the configs up later - at my current location I cannot...

Thanks for the help,


jdcrowder Tue, 12/04/2007 - 12:39

I have fixed my problem.

It turns out the problem was how I had the WAN.

I have a "Border" 1712 router if you will, where my ISP line comes in.

The reason for this is because they gave me one static IP - and then a pool of addresses - and they are on different subnets. So I have to route my traffic to the gateway of the static address. It is really retarded but we are dealing with it.

Anyway - I guess when I plugged the 3524 switch into the trunk line it messed up the trunk with the 1712 border router.

I am no longer switching that connection, it is plugged directly into the 2801 router. Everything seems to be working fine.


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