L2 is a switch.
With two switches, you can run redundant connections from the server nic to each of the switches, thus providing redundancy. You can also connect a number of hosts to the L2 switch.
Also if you run a LAN based failover, between the two PIX, then you ll need to link the pix failover interface to a switch or use a cross over cable (atleast).
Sankar Nair
UC Solutions Architect
Pacific Northwest | CDW
CCIE Collaboration #17135 Emeritus