an answer to you first question. Imagine you have a pix with one outside interface and one inside interface and a 4-port switch connected to this inside interface. This pix 501 puts this together in the same device.
This also answers your second question, you can only configure the 'virtual' inside interface of the pix. The real physical inside interface is provided by a fast ethernet 10/100 switch.
The Pix501 only has two interfaces; Interface0;Interface1. Interface0 being the outside interface and Interface1 being the inside interface. Interface1 is comprised of the 4 port switch. The switch is not managed except for the interface so you get an auto config negotiation for each port.
The Pix 501 wasn't desinged like the Pix 520 which you can have more then two interfaces. If you really need to accomplish control of more then two ports (like for a DMZ) then you will need a higher pix model.
I'm sure Cisco could better ansewer the design rational behind the PIX 501.
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...