Remote router issue

[kdowner]

My company has offices through out the state connected by cisco routers using point-to-point connections.I can telnet and ping each router from my computer at the central office but when I try to ping my workstation from the remote router it fails. Only the routers located at the central office can ping my computer sucessfully.

[jamey]

When you telnet/ping from your PC to the remote routers, are you telneting/pinging to the router's ethernet or serial IP? I suspect you are telneting/pinging to the remote routers ethernet IP.

My guess is your PC has a default route to some router at your central site which does not have routes to your point to point IP subnets. When you ping from a remote router, it will use the serial IP as the source IP. My guess is your PC doesn't know how to get back to the serial IP. Of course this is just a possibility.

To verify this, you could try doing an extended ping to specify the source IP of your ethernet interface or the interface you want the ping sourced from on the remote routers like this:

This example specifies the source by interface

router#ping

Protocol [ip]:

Target IP address:

Repeat count [5]:

Datagram size [100]:

Timeout in seconds [2]:

Extended commands [n]: y

Source address or interface: FastEthernet4/16 (or whatever your ethernet interface is)

Type of service [0]:

Set DF bit in IP header? [no]:

Validate reply data? [no]:

Data pattern [0xABCD]:

Loose, Strict, Record, Timestamp, Verbose[none]:

Sweep range of sizes [n]:

This example specifies the source by IP

router#ping

Protocol [ip]:

Target IP address:

Repeat count [5]:

Datagram size [100]:

Timeout in seconds [2]:

Extended commands [n]: y

Source address or interface:

Type of service [0]:

Set DF bit in IP header? [no]:

Validate reply data? [no]:

Data pattern [0xABCD]:

Loose, Strict, Record, Timestamp, Verbose[none]:

Sweep range of sizes [n]:

-HTH

[vcjones]

There are numerous situations which could cause these symptoms. Some items to keep in mind:

When the router pings you, it will use the IP address of its serial link. Can you ping that address from your workstation. Remember for ping to work, there must be a working route for both the ping packet and the response to the ping packet.

If you are telneting to the same address the router is using to ping you, are you going through a network translation filter or firewall? If dynamic NAT is involved, your external address is only defined when you initiate the transaction. Similarly, the firewall may be configured to block unsolicited attempts from the outside to reach you. Note that the firewall does not need to be a separate box. It could be part of the router configuration or software running on your computer.

Good luck and good hunting!

Vincent C Jones

http://www.networkingunlimited.com

[kdowner]

That does help I did not remember that by default when pinging from the router to another device it is using the serial interface. The problem is I want to backup router configs remotly using a tftp server but when trying to do so I get a failure error. Any suggestions.

[jamey]

You want to be sure you can ping the serial IPs of the remote routers from your PC. Once you can do that, tftp will probably work from ok assuming there are no ACL/filters in the path.

I don't know how you have your network laid out but I assume your PC's default gateway is some router at the central site. Make sure that router has routes to the "in between" serial IP subnets, not just the ethernet side of the remote routers. You may have multiple hops at your central site before the remote sites are reached. Just try and ping the serial IP of a remote site router from each hop along the path from your PC to the remote site router. If you find a hop that can't get to the remote site router serial IP, add a route to the remote site router serial subnet via the next hop router in the path.

-HTH

[kdowner]

Thank you for your help that solved it.

[vasista]

Check if the gateway settings on your work station are right

[chuck.price]

Also check any firewall settings if you use one.

[kdowner]

There isn't a firewall between offices because all internet access has to past through the central office which is firewalled.