Trouble with NAT

mcandial1 · ‎06-11-2015

Hi! I'm having issues with a configuration on an odd scenario.

I have a Cisco 888 (G.SHDL) that is connected as a p2p with the BBIP of an ISP via ATM interface. I need to connect to the ethernet, devices to access to the internet (access point). Usually you would use atm interface as nat outside but my problem is that the p2p connection is use for administration only. The ips (usually a /30) are not public ips (not suitable for NAT) So I need an interface to use as NAT outside and direct all the LAN traffic to it.

I've read some of NAT on a stick but I'm not entirely sure if that's my answer. I thought on using a loopback with an IP suitable for NAT and redirect all the LAN traffic from interfaces connected to those devices to the loopback but I'm not sure how to do it.

Any ideas?

Thanks in advance.

Richard Burts · ‎06-11-2015

I am confused about the environment described here. It seems to describe an 888 with a connection to an ISP. But it says that the p2p connection is for administrative purpose only. So my first question would be whether this 888 has access to the Internet? If so how does it access the Internet? I might guess that it does access the Internet and that the ISP takes the address from the router on the p2p and does a translate on that address. Can the original poster clarify whether this is the case?

HTH

Rick

HTH

Rick

mcandial1 · ‎06-12-2015

Hi, thanks Rick for you thoughts.

The 888 has on it´s atm 0.1 interface an ip to make the p2p with ISP backbone. That ip is not suitable for nat, it is only advertised in the ISP network. On the fastethernet interfaces you can provide with a pool of ip suitable to access the internet. Usually the customer connects another router to on of those eth interfaces and gets an internet published ip and use it to nat (an ADSL modem for example)

My issue is that I need to connect access points to those eth and have another interface use as nat outside. Usualy you will use atm0.x with an ip to NAT but I can´t do it in this case.

Hope now it's clear.

Richard Burts · ‎06-13-2015

Unfortunately it is now not clear at all. You have failed to answer my first question which is whether the 888 has Internet access (from the 888 can you ping or otherwise access) some resource in the Internet. Please answer this question and then we can take the discussion from there.

HTH

Rick

HTH

Rick

mcandial1 · ‎06-15-2015

No, it doesn´t have internet access with the atm0.1 ip I've described.

paul driver · ‎06-12-2015

Hello

If I am interpreting this correctly ( maybe I am not!)

When you say the ips are not public - do you mean the addressing coming in from the ISP is private-meaning the ISP is already natting for you.

And when you say the ethernet devices you mean internal hosts attached to the ethernet module of the 888?

In that case I guess all you need to to create a SVI interface on the 888 with an internal ip range of your choice and set ip default route pointing towards your wan ( ISP LAN) interface.

If you wish for dynamic addressing for these internal hosts then you could also apply a dhcp service on the 888.

res

Paul

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Paul

mcandial1 · ‎06-15-2015

I've figured this out. I use ip nat enable on vlan, loopback (with an ip capable of nat) and atm 0.x (for p2p) interfaces

It finally connected the dots as I need it. Now it´s working.

Richard Burts · ‎06-15-2015

I am glad that you have figured a way to get it to work. Thank you for posting back to the forum to let us know that you have found a solution for your issue.

HTH

Rick

HTH

Rick