Learning Lab

[mrtylergreen]

Hello,

I got an associates degree in Networking several years back, but got out of the business for a while and my skills have lapsed. I am in the process of re-learning basic techniques of Cisco router management and I have run into a brick wall! Right now, I have a lab set up with the following set up:

1 Server with no services installed yet

The server is connected to a Cisco 3725 by Ethernet, the Cisco 3725 (I will call it R1) is connected by serial interface to another Cisco 3725 (I will call it R2). R2 is connected by ethernet to a gateway router with Internet connectivity.

It is subnetted as follows:

Server IP- 172.16.0.254 <--172.16.0.0/24--> 172.16.0.1 -R1- 172.16.255.1  <--172.16.255.0/30--> 172.16.255.2 -R2- 172.16.255.5 <--172.16.255.4/30 --> 172.16.255.6 INTERNET GATEWAY--->Internet

R1 and R2 are configured for EIGRP to advertise network 172.16.0.0 R2 has a static ip route 0.0.0.0 0.0.0.0 172.16.255.6 and is configured to redistribute static routes.

R1 shows 172.16.255.2 is the gateway of last resort, but if I try to ping an internet address (such as 8.8.8.8), not only does it not make there but if you debug IP packet on R2 it never even reaches R2. However, if you ping 17.2.16.255.6 all the way from Server you get a response.

How is it possible that R2 knows how to get the internet and Server knows how to get to what R2 is connected too, but server will never connect to the internet? R1 also does not reach internet, but it does reach the interface that R2 is connected too.

I am beating my head against a wall right now, and any help will be appreciated!

[paul driver]

Hello
Can you post the config of the routers

Also sounds your internal ip range is natted

This private ip range cannot be routed on the public internet so it needs to be translated into a public ip.

Res
Paul


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[mrtylergreen]

The internet connectivity device does NAT. Internet connectivity is through a home netgear router that does NAT to a cable modem to the internet. I am at work right now, but I will post the running-config and routing tables when I get home tonight. I am pretty sure (please correct me if I am wrong) letting the home device do the NAT is okay because R2 has internet access even though R2 is on a subnetted private IP range. Only R1 and the server connecting to a segment connected to R1 don't have internet.

[Harold Ritter · Accepted solution]

Hi Tyler,

The netgear device probably does NAT only for the directly connected LAN interface, hence R2 geting Internet access but not R1 nor the server. The other thing you could do is configuring NAT on R2 using the outside interface address.

Regards

[mrtylergreen]

Yup. I configured a nat pool with overload and it works now! Thank you, this has been a valuable lesson in NAT's relationship to other networks!