Configuring DNS for Cisco Pix 501

Posted on 2007-03-28
Last Modified: 2010-04-09
When setting up a Cisco pix 501, do I need to set the DNS server for a static outside interface? For example:
I have static outside:

static inside (no DHCPD):

I want to allow all users on the inside to web browse through this pix (enabled PAT)

So I have been told by my ISP that I should set my DNS servers to x.x.x.x & x.x.x.x - where & how should I configure those numbers? I have looked over the PDM interface, and see no place to set the DNS server addresses.
Question by:NTNBower
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LVL 19

Expert Comment

ID: 18811429
hi there

If the PIX is not doing dhcp for you, then you don't assign the DNS addresses on the PIX for the users benefit.  The DNS servers are required for users to browse and are defined in the dhcp pool or statically on the pcs themselves.


Author Comment

ID: 18811495
Right now they have a PC with two NIC cards and Zone alarm - we are trying to replace this PC with the Pix. I will test this out and let you know what I determine.

Thanks for the rapid response.
LVL 19

Expert Comment

ID: 18811702
no probs - good luck
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Author Comment

ID: 18811719
Turns out the current set up is using WinProxy for hte users to connect. SO I would need to replace that functionality - is it possible with the PIX
LVL 19

Accepted Solution

nodisco earned 500 total points
ID: 18812234
No - the PIX is not a proxy server - its quite possible that the only reason the proxy was in place in the first instance is that you didn't have a firewall (zone alarm is no substitute for a proper hardware firewall).
In order to replace the "functionality" you need to know what you are replacing.  If the PC was acting purely as an internet gateway with very basic firewalling, then the PIX will be a far better and more secure solution than what you currently had.  You need to configure the PIX to have an inside ip (the pcs default gateway) and an outside ip on the internet.  You can then nat/pat the internal hosts to public ip and allow them out.  The PIXs ASA algorithm does not allow traffic from the outside to inside by default - unless you specifically allow it.  All traffic is allowed out by default - unless you dictate otherwise, so you have a great control on what your users and public ip can do.
You also have vpn client/pptp termination, hosting, dhcp and a range of other options open to you.  If you are unsure on how to setup the PIX, go into the PDM wizard and follow the steps - or post your config (with passwords removed) and we can assist.


Author Comment

ID: 18813111
So to continue with this operation, about all they could do is replace zone alarm with the Pix, and then they would need to keep the proxy - so:

Internet >> Cisco Pix >> PC with WinProxy >> Internal network

Currently, there are only a handful of users in my network that are the ones using this connection (it is controlled). The rest are going through the default GW for the entire network. Would it be possible to use the PIX if each individual PC were configured to use the PIX for web & GW for everything else? Then we could eliminate the need for the proxy?
LVL 19

Expert Comment

ID: 18813299
Yes - I would use the pix as gateway and get rid of the proxy server.  

Author Comment

ID: 18815480
I knew something was not right and would not work - just could not put my finger on it. I think we have it now and I believe I could use the PIX, but would need to:

Set on all local PC's wanting to use it:
Set PIX as GW
Set DSN for other side of GW (e.g. ISP)
and set up a Static route for the Local WAN/LAN to use the other GW

Thanks for helping me see the forest through the trees - some times it gets foggy in there!
LVL 19

Expert Comment

ID: 18819652
no probs - you have it sussed right there ^^.  cheers

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