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2 External Interfaces on PIX with Wireless router on one External

Posted on 2009-04-02
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I have a PIX firewall with two external interfaces. One interface has our AT&T DIA and one has AT&T DSL. We have the PIX set up to use the DIA for the default route with metric 1 and the DSL for the default route on metric 2 (back up Internet connection basically). Currently, we have a wireless router on the DSL line mainly for our vendors/auditors when the come in so they can have access the the Internet.

I would like to make it so that you can VPN into the PIX on the DIA if we have a laptop on the wireless in part of the building without a network jack. With the security rules in place, I cannot connect to the DIA public IP from the DSL because of reverse path check.

However, I could add a default route on the outside interface for the ip address of my wireless router to the gateway ip address for the DSL modem.

i.e. modem=172.16.1.1 , router=172.16.1.3   ------   route outside 172.16.1.3 255.255.255.255 172.16.1.1
(example IP addresses. I have a public IP address for this router and modem)

This allows me to then connect to the VPN on the DIA public IP from the wireless on the DSL.

Now my question though, am I leaving myself open to a security issue?

The only incoming rules from the DSL interface are currently

~ implicit to permit scr 'any' dst 'less secure networks' to service ip, and
~ implicit deny rule any any

Thanks in advance for your comments/suggestions.


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Question by:Lee Anderson
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by:asavener
ID: 24055029
Why not just VPN to the interface that's on the same subnet as the wireless router?
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Author Comment

by:Lee Anderson
ID: 24059105
Yeah I guess I could do that.

What I was trying to do which I failed to mention was to make it so that my users could continue to use the host name on our DIA (mail.mydomain.com) for their connection entry in the VPN client.

Another reason I was looking at this is because I have one user who is a contracted employee through a third party who does not connect to our network except for OWA. He has offices at each of our locations and he uses the DSL lines at those locations to connect to our OWA server. Well when he is our main location where the OWA server and firewall are at, he cannot connect to the OWA server using https://mail.mydomain.com/ becuase I would guess that the DSL is taking the next hop to the firewall but becuase of the reverse path check the firewall is denying the traffic.

The route addition I mentioned in my original post, resolves both issues but I just wanted to make sure that I wasn't opening myself up.

I guess I could just give my users an addition VPN Connection Entry for when they are on the DSL and port forward 443 for OWA and give my other user the URL for the OWA on the DSL interface.
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asavener earned 1500 total points
ID: 24059311
OK.

Re-reading your original post, it appears to me that your failover configuration will only work if the primary outside interface goes down.  IMO, that's not terribly useful, so another option would just be to disable the secondary outside interface, and then do a manual failover if you have an extended outage.
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Author Comment

by:Lee Anderson
ID: 24060364
That is how we have it set up. It is failover to the DIA and as you mentioned it;s not terribly useful as the DIA has not dropped in the last 5-6 years. I hadn't thought about just disabling that interface and manual failover later.

Thank for the sugestion. I think I will go that route.
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