08-20-2007 03:48 PM - edited 03-11-2019 04:00 AM
I have read the following definition a couple times:
Transparent mode, the FWSM acts like a "bump in the wire," or a "stealth firewall," and is not a router hop.
What I understand with the previous sentence is that: The FWSM connects the same network on its inside and outside interfaces, but each interface must be on a different VLAN.
However, are both vlans going to share same subnet???
08-20-2007 04:06 PM
Transparent firewall will bridge between vlan and not route, so if you are using different subnets you will need layer 3 routing device to route packets between subnets.
~Rohit
08-20-2007 10:57 PM
Hi
In answer to your question yes you have 2 vlans but only one IP subnet. This setup is also used on other devices such as load balancers.
The reason you need to do this is to avoid a spanning-tree loop. Assuming you are running PVST+ then having 2 vlans but only one subnet allows you to bridge the subnet with the FWSM.
HTH
Jon
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