Help conf 2651XM router for use w/ Optimum static ISP

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May 30th, 2008
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I just had Optimum Business Static IP service installed. It comes with 5 useable public static IP addresses. They supply a cable modem, which is connected to their Cisco 800 series router. The 800 router is locked down and they say it is in bridge mode (I believe). I have access to the 800 router. The 800 router is IP 96.x.x.113. I have 5 IP addresses 96.x.x.114-118 to use. They recommend I connect my router to the 800. The 2651XM has 2 fast ethernet ports I planned to use, but I have had no luck yet.

I assigned fa0/0 96.x.x.114 and I can ping out. I want to be able to use 115 for my web site in front of my firewall. I will assign 116 to the firewall for NAT. I will have two servers behind my firewall which will get 117 and 118. All the rest behind the F/W will get private IP addresses.

My problem is being able to use only one public IP on the 2651XM and still get it all to work.

Currently, I have T1 with my soon to be old ISP connected to a Cisco 2524 with a Serial0 and Ethernet0. It uses IP Unnumbered, so it only uses one IP. It does not seem like I can use that on the 2651XM.

FYI, if I connect a PC directly to the 800 router, I can ping it and ping out fine and browse the net. My problem is definitely the 2651 conf.

Finally, do I really need the 2651? I originally thought I did. I will only have my webserver and firewall directly connected to the 800. The rest of my network will be behind the firewall.

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Overall Rating: 3 (1 ratings)
PAUL TRIVINO Fri, 05/30/2008 - 08:47
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If you have assigned 96.x.x.114 to the Fa0/0, you *have* assigned only one public IP to the 2651, that's fine.

Given what you've described, I'd say you don't really need the router, everything you want to do can be done on a (decent) firewall.



OptimusBob Fri, 05/30/2008 - 09:53
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So, I guess there is no real benefit from having the 2651XM router in between the Cisco 800 and a Cisco switch with connects to the webserver and firewall. I don't want to open up a can of worms.

If there is a benefit, I will need help configuring the 2651XM to use one IP addr and route correctly between fa0/0 and fa0/1.


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