How do I configure router to provide both NAT and IP address pass-through?

[jetsongeorge]

We currently are assigned several /24 blocks from our backbone provider. We have allocated static public addresses to each end-user on our network.

We have obtained a new backbone provider with different IP addresses. On an interim basis, we would like to use either a Cisco 2821 or 3825 to connect the existing IP network to the new IP network. Each router has two Gigabit ports (Ge0 and Ge1). (along with various other expansion cards, t1 etc)

For example, the idea would be to connect the new network to Ge0 and the existing network to Ge1. The existing IP addresses from the existing users

on Ge1 would be converted to one of the new addresses using the NAT function of the router and handed off to Ge0. As we define a new IP address to a user, it would  just be transparently passed through intact from Ge1 to Ge0. Ultimately, the old addresses will be phased out.

Can you tell us if this is feasible and if so can you help with the config file parameters?

Thank you in advance,

[jetsongeorge]

No suggestions? We could really use some help.

Thanks.

[ryates_presido]

I need to make sure I understand this. Can you put a drawing up? It should Be ablest be done with policy based routing and nat bypass on the routers. One of them or a combination of both would make it work. Afet seeing the layout and what you want to do I might be able to help

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[ryates_presido]

This should provide info on nat and nat bypass

http://www.cisco.com/en/US/tech/tk648/tk361/technologies_tech_note09186a0080094e77.shtml

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[jamiegrive]

You could just enable NAT on one port with 'IP NAT Inside' and not have it on the other port, thus not being eligible for NATing. Or have I misunderstood your question?

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[jetsongeorge]

Thank you for your comments. We will review the article listed and see if it helps us sort this out. We have attached a current configuration and proposed configuration diagram. We'd appreciate your comments.

Thank you again,

George

[jetsongeorge]

We have looked over the article on NAT configurations. We will likely be able to use it. Thanks.

The only trouble with the article is that each senario shown uses two ethernet ports and a serial port. Can we do this just using the two Gigabit ports on the router and not use a serial port?

[ryates_presido]

Yes you can just set one to inside and one outside. Does not matter what type of interface.

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[ryates_presido]

Yes it is any kind of interface you can use it on. One will be inside and one will be outside.

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[jetsongeorge]

Thank you. We'll work on the project using the information above. We'll update the post later in the week on how it went. Thanks again,

George