Hello,

We have a 3324 that has two different ISP's plugged into a single vlan that distributes to two firewalls.  It's essentially acting as a dumb switch.  We had recently upgraded our ISP to a higher speed which the 3324 doesn't support since it's 10/100.  We had a spare 5324 that I was going to transition over to.  I configured the switch exactly the same and plugged in the lines. 

However, only one ISP was working.  The other was dead.  There weren't even any link lights for that ISP line.  I combed through the settings and tried a few different settings, but nothing was working.  I decided to go back to the 3324 and run a line to the 5324 to do some testing. 

I was initially not getting any traffic, but I disabled STP on the port that came from the 3324 switch and I was able to get traffic.  I decided to leave it disabled and try the swap again.  Again, it did not work.  The link lights were dark once again.

Would there be any reason why the 5324 is blocking the ISP traffic?  I tried plugging in a dumb switch and it worked immediately as well. 

Any help is greatly appreciated.