Can't ping anything from router?

Unanswered Question
Feb 2nd, 2007

I have a Cisco 837 ADSL router set up as a Site-toSite VPn to our Cisco Concentrator. I can ping the router from my laptop from the head office where the Cisco Concentrator is and users on teh LAN where the Cisco 837 is based can ping me and the servers - great, and everything works fine. But if I telnet onto the router and try and ping from there to say my TFTP server or any server/pc it can't? There are no firewalls in between. I can post the config if you want.

I have this problem too.
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mheusinger Fri, 02/02/2007 - 00:34

Hi,

as you can telnet into your router we can safely assume IP connectivity is given.

Have you tried "ping source "? Specify the interface with the IP you are using for telnet, as per default the outgoing interface IP is used, which might not be routed correctly in your network.

If this does not work then you have some functionality preventing ICMP but allowing Telnet packets. Both applications use the same source and destination IP and thus connectivity is broken at layer4 (or higher).

Second test traceroute from the router to your PC with the "telnet interface IP" as source.

Can you please try and come back with the results?

Regards, Martin

whiteford Fri, 02/02/2007 - 01:26

Thanks for your quick reply Martin,

I did what you said with good results:

Router#ping 192.168.1.111 source 172.19.3.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 192.168.1.111, timeout is 2 seconds:

Packet sent with a source address of 172.19.3.1

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 24/33/44 ms

Router#

How can I know make sure I can TFTP the config to 192.168.1.111?

mheusinger Fri, 02/02/2007 - 01:33

Hello,

configure the router to use the interface with IP 172.19.3.1 as source for TFTP:

Router(config)#ip tftp source-interface Loopback0

Replace Loopback0 with the respective interface in your router. Additional commands with similar result for other protocols:

ip telnet source-interface ...

ip ftp source-interface ...

Hope this helps! Please use the rating system.

Regards, Martin

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