- A virtual community of network engineers
 Home  BookStore  StudyNotes  Links  Archives  StudyRooms  HelpWanted  Discounts  Login
RE: PIX Design Considerations [7:48979] posted 07/17/2002
[Chronological Index] [Thread Index] [Top] [Date Prev][Date Next] [Thread Prev][Thread Next]

Hi Richard,

The simple answer to your question is "yes you need a seperate router
outside the pix".  Leave your internal router alone and just add a default
route pointing at the pix interface .   

He doesn't necessarily have to be using VLANS as long as all the subnets is
routing for are on the same lan segment than the router just routes between
ip networks on the same wire.

The router you add to the scenario would be on the outside of the pix, and
would usually be connected to the  internet via a serial line, or possibly
another untrusted network.  This router than becomes the default route for
the pix itself.

You need to add a route inside command on the pix to route to the other
subnets hanging off your internal router.

You are correct, the pix performs some routing funtions but is not a fully
functional router - so you can't have things like secondary ip's on a pix
interface, therefor you need a device behind the pix that can route between
your internal networks.

outside router------pix------internalrouter----ip-segment

hope this helps,


-----Original Message-----
From: Robertson, Douglas [mailto:Douglas.Robertson@xxxxxxxxxx]
Sent: 17 July 2002 15:50
To: cisco@xxxxxxxxxxxxxx
Subject: RE: PIX Design Considerations [7:48979]

I am not sure I would class a PIX as a router in the true sense of the word,
yes it does route traffic from interface to interface but would I use it as
a router, NO, it only supports ONE routing protocol RIP, that does not
constitute a good router in my eyes. 

Now to the question, just reading the description (I may be
mis-understanding the topology a bit) but it sounds like you have one router
ethernet interface with subinterfaces with separate subnets going to a
I do not see how the switches are not running VLAN's and the interface must
have ISL or 802.1q. Or you don't have subinterfaces but secondary addresses.
The PIX does not support subinterfaces or secondary addressing on any
interfaces, so in this case you would require a router.


-----Original Message-----
From: Richard Tufaro [mailto:rtufaro@xxxxxxxxx]
Sent: Wednesday, July 17, 2002 7:47 AM
To: cisco@xxxxxxxxxxxxxx
Subject: Re: PIX Design Considerations [7:48979]

Why don't people get the notion that a "Firewall" is essentially a router.
PIX = Firewall = Router... Firewall = Router. It ROUTES....

>>> "Jeffrey Reed"  07/16 8:19 PM >>>
I?m still pretty green with PIX in general and was talking today about
introducing a PIX into an existing network. The customer has a router (not
controlled by them) that has three public class C subnets defined. They are
not using VLANs, so the router has an interface and two sub-interfaces going
into a switches network. We want to put the PIX in between the outside
router and the LAN. I know this group has said several times the PIX is not
a router. Do I need to have another router between the PIX and the LAN to
perform routing between subnets? I assume the PIX will not facilitate
routing between the internal subnets. Can you define multiple interfaces on
the internal interface of the PIX if we didn?t need to route between the
internal VLANs?

Any suggestions would be appreciated!

Jeffrey Reed
Classic Networking, Inc.
Cell 717-805-5536
Office 717-737-8586
FAX 717-737-0290
This email and any files transmitted with it are confidential and
intended solely for the use of the individual or entity to whom they
are addressed. If you have received this email in error please notify
the system manager.

This footnote also confirms that this email message has been swept for the
presence of computer viruses.

For more information contact postmaster@xxxxxxxxxxx

phone + 353 1 4093000

fax + 353 1 4093001


Message Posted at:
FAQ, list archives, and subscription info:
Report misconduct and Nondisclosure violations to abuse@xxxxxxxxxxxxxx