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New Member

Multiple Subnets using 10.x.x.x attempting to route over 678 DSL NAT

I have 3 small sites connected over T1 using Cisco 2500 series routers. Site A - 10.2.X.X mask 16, B 10.1.X.X 16, and C 10.3.X.X 16. I now have a DSL 678 connection to the internet at Site A. I have the 678 set to be the default gateway for the 10.2.X.X 2500 series router using a valid IP on the inside network 10.2.255.253. I have NAT enabled on the 678. I can go out the Internet on PCs in the 10.2.X.X network but can not at the other sites. A Ping fails from the 678 to the outside address of the 2500 router. I tried to add static routers to all networks 10.3.x.x and 10.1.x.x to use the 2500 series router on the 10.2.X.X network but it still does not work. Is the Nat table - 10.0.X.X conflicting with my internal network scheme? Am I not adding the route lines correctly? Thanks

3 REPLIES
New Member

Re: Multiple Subnets using 10.x.x.x attempting to route over 678

I'm not an expert on the 678, but I believe that by default it does NAT and DHCP, the default NAT pool is 10.0.0.0 and the default address of the 678 to the inside network is 10.0.0.1 (I don't recall the mask). It is best to use some other address range in this situation. I believe that your choices are 1) change the addressing scheme on your internal network; 2) reconfigure the 678 to use a different range in the NAT pool and a different address on it's Ethernet port; or 3) double NAT. I would choose door number 1 if it is not too much trouble or door number 2 as a second choice. I would avoid door number 3 unless you are looking for adventure.

New Member

Re: Multiple Subnets using 10.x.x.x attempting to route over 678

It will be a tough go changing my internal network addresses - multiple servers and routers. I tried to change the NAT Pool for the 678 but can not find any commands that allow it. Is it Possible? I am about to head to door 3 - would I enable NAT on my 2500 series router?

New Member

Re: Multiple Subnets using 10.x.x.x attempting to route over 678

First you must make sure that both site A, B and C can reach the 678.

I don't know the 678 router, but if it's like other cisco IOS routers yout NAT configuration could look somtingh like this :

interface

ip nat outside

.

.

!

interface

ip nat inside

.

.

!

access-list 10 permit 10.0.0.0 0.255.255.255

ip nat inside source list 10 interface overload

!

I don't know if it was this you was looking for, but i hope it helps you.

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