IP Routing/Forwarding

[tek777]

Here is my setup.

Adtran CSU/ROUTER T1 bundle 624----LinkSys Switch----Network

The ISP issued us a block of 15 IP addresses. So the subnet is 255.255.255.240, and Gateway is x.x.x.209.

Everything works great if you do 1 IP per 1 Interface, say 6 Public IPs and 6 Servers.

I am having an issue getting multiple public IPs to a single interface, like the Pix firewall. I do a Static command for the 2nd Public IP and it seems it cannot see it because it doesnt know about the route. I check the arp cache and it doesnt show the mac for the interface I did the static on. I try to connect to the Static IP from the internet, no dice. I can only connect to the actual IP of the interface.

The last admin used proxy arp, but I am not sure if this is the correct way of doing things. If i used proxy arp, I would need to have the same MAC on all of the public IPS. Or the only way I could use the public IPs would have to be behind the device I specified the 255.255.255.240.

Could it be the way the switch tries to use 1 Mac per Port? If i used a hub connected to the router, would that help any on my pix firewall.

I am thinking I could use windows to do IP forwarding, but I would rather not, being that it would be on the public IP.

To make matters worse, I do not have access to the Adtran router. I know to do NAT, but it doesnt seem to recognize any IPs that are not hardcoded to an ethernet card or interface.

Thanks for your help!

 

[tek777]

I am thinking maybe i need to create 2 subnets ontop of the 240, by using a 255.255.255.248. This will use my x.x.x.216 as the "subnet" address. and then I can use a few of the higher IPs. I am just not sure where to point my pix as the gateway. the 255.255.255.240 was pointed at the gateway of 209. For this 2nd subnet on 255.255.255.248, I am thinking I should point it at 216 as the gateway. I am also thinking I need to do Nat between the 240 into the 248. Still floundering around with this though, heh. thanks....

 

[tbilan]

Your network map is too vague. Is there a Pix the picture somewhere? What are you trying to configure.

What do you mean multiple public IPs on a single interface? Interface of what kind of device? NT server, router, firewall etc.?

Proxy arp is fine if you're trying to put a firewall between their router and your network and you want to pass the IPs through the firewall without subnetting and losing addresses. This is essentially what a Pix does when you static 2 addresses together where the Pix reports its MAC as the owner of the public IP to the internet router etc.

Post your configs and people we'll jump in and make suggestions.


Tom Bilan
TJBA, Inc.
CCNP, CCDP, MCSE & CNE