How can I use LAN ports ONLY on a Linksys Wireless WRT54G?

Posted on 2008-06-15
Last Modified: 2010-04-21
I want ALL packets to stay on the LAN.  I tried putting in a static route:

But it said "invalid destination IP".

The reason I want to do this is I am hooking up the WRT54G to the inside NIC card of an ISA2004 server, which is acting as the gateway to the internet.  

So I don't want to have a second gateway on the network and I don't want to have a second set of inside addresses.

Is there a way to make this work?

If it can't be done with the WRT54G, is there a wireless router I can buy that allows me to do this?

Question by:gateguard
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Expert Comment

ID: 21788187
Have you tried to use the ISA server as your default gateway on your linksys.

Author Comment

ID: 21788216
I'm not sure I understand.  The linksys has two configuration settings, one of the LAN the other for the WAN (or internet).

If I set up the LAN to have this address:

And the inside nic of the ISA server to have this address:

And have the wireless give out addresses in the range

And then connect to the wireless with a laptop and try to go to the internet, I can't get to the internet.

It seems the wireless is trying to route the laptop's request out to its "internet" port, even though it's not plugged in.  Or anyway, it's failing.  (I can get to the internet from the ISA server.)

I'm not seeing what else I can do to route all packets on the wireless to


Accepted Solution

Nyah247 earned 167 total points
ID: 21788338
Ahh...  The ISA server should not have an internal gateway just one on the external interface.  You need to make sure that you setup the routing tables on ISA for internal.  Check this out for how to add routes:

Check out the info about static routing with linksys here:

Author Comment

ID: 21788439
Thanks but I think I've got the ISA correctly set up.  If I take out the router, plug in a switch in its place, plug a PC into the switch and manually give it an ip address of, then that PC can get to the internet.

But if I remove the switch and put the wireless router back in the circuit, then I'm back to the problem of not being able to get to the internet from an inside computer.

The problem appears to be that I can't enter this static route on the WRT54G:

Sending all packets, whatever their destination, to the ISA server.

When I try to enter that route, I get "invalid destination IP address".  

Of course, in the "real" world, is NOT an "invalid destination IP address".
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LVL 44

Expert Comment

ID: 21788770
Did you try plugging the ISA's inside NIC into one of the WRT54G's LAN ports, not its WAN/Internet port?
LVL 44

Assisted Solution

Darr247 earned 167 total points
ID: 21788796
> If I set up the LAN to have this address:

Just for clarity, that's
LAN interface -
Subnet mask -
Gateway -


If so, I'm not understanding

> And the inside nic of the ISA server to have this address:

i.e. The 'inside NIC' should NOT have a Gateway IP of

Assumption - You've also restricted the scope of any other DHCP server[s] to not hand out addresses from 100-150, and don't have any static IPs in that range, so you won't end up having devices with duplicate IPs 'inside'.
LVL 88

Assisted Solution

rindi earned 166 total points
ID: 21788820
Just give the router a static IP on your LAN's subnet. Make sure that IP isn't served by your DHCP server and disable the DHCP server of your router. Connect it to the LAN via it's LAN port. Don't use the WAN port.

Author Closing Comment

ID: 31467325
Thanks for all your help.  One thing I added to the mix was turning on RIP on both the server RAS and the Linksys router.  That finally gave me the route I needed on the Linksys.

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