Re: Cisco 2500 routing question

ishcoleobo · ‎10-07-2003

I am trying to get my Cisco 2500 series router to ping the outside world. I have a linksys router/switch that my isp comes into with a lan ip of *.*.*.1, and the Cisco router is assigned the ip *.*.*.230. The user computers range from *.*.*.100 - *.*.*.200. After setting up the Cisco 2500 with that address I went into global configuration and set the default gateway to 192.185.1.1 with the command:

"ip default-gateway 192.185.1.1"

When I try to ping out from the router to:

yahoo.com

It locates the ip address via DNS, but is not able to ping it.

This does not make sense to me, because I figure that if it can see yahoo.com through the gateway to get the address, it should be able to ping it. If anyone has any advise that they could offer me it would be greatly appreciated.

Thank you,

Russell Pidwell

milan.kulik · ‎10-07-2003

Hi,

please clarify what is your topology.

Is your ISP connected to the 2500 serial port, the 2500 Ethernet port connected to the Linksys switch and users connected to the Linksys switch? (This is a standard topology.)

If yes, you should configure the 2500 Ethernet port address as default-gateway on the user PCs. You shoud also configure default route on the 2500 via command

ip route 0.0.0.0 0.0.0.0 next_hop

where next_hop is the IP address of the ISP router serial port.

The "ip default-gateway ...." defines default gateway address on L2 devices (switches, e.g.), not the default route on a router.

OR is your topology following:

The Linksys works as a switch/router connecting your network to the ISP, PCs are able to connect to the Internet already, and you are connecting additional router via an Ethernet port?

If yes, just configure

ip route 0.0.0.0 0.0.0.0 next_hop

where next_hop is the Linksys LAN interface IP address (the same as the default gateway value on the PCs) on the 2500.

If you locate the ip address via DNS, you don't have to be able to ping it.

It means only that your DNS server is able to talk to another DNS servers, not to the target directly.

HTH,

Milan

ishcoleobo · ‎10-07-2003

I am the second topology that you speak of, I also tried to do the "ip route 0.0.0.0 0.0.0.0 *.*.*.1" and still could not ping. Any other ideas?

deilert · ‎10-08-2003

I beleive you will need to set the next hop of your default route to the ip address of the linksys that the ISP is giving you

ishcoleobo · ‎10-08-2003

How do i set the next hop on my default route.??

deilert · ‎10-09-2003

ip route 0.0.0.0 0.0.0.0 ipaddressofnexthop

i.e if the next hop is 172.16.1.1

ip route 0.0.0.0 0.0.0.0 172.16.1.1

milan.kulik · ‎10-08-2003

Are your PCs and the 2500's Ethernet port in the same subnet?

Is the *.*.*.1 the default gateway address configured on the PCs?

Are you able to ping from the 2500 to *.*.*.1?

What's the difference if you try traceroute some Internet target on the 2500 and compare it with the traceroute output from a PC?

Regards,

Milan

Keyurp · ‎10-09-2003

In order to troubleshoot your network you have to make sure that your computers are in the same subnet. Furthermore, also make sure that your DNS servers/Routers/Switches are also properly subnetted.