Dedicated T1 point to point 1720 router

Unanswered Question
May 5th, 2007

We have a point to point tunnel. This was working fine until today afternoon and since then it stopped working I cannot figure out what happened. I can ping the LAN side of other side just fine when I am pinging from within router after telnet to it but I cannot ping it from our LAN of after attaching single computer to FastEthernet0.

After attaching the computer towards FastEthernet0 I can ping the interface FastEthernet0 and I can also ping the interface Serial0?s IP but I cannot ping it to the other side?s interface Serial0.

After I telnet to my router I can ping my side of LAN their side of router and their side of LAN. Any help will greatly be appreciated.

I have this problem too.
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omar.ghoneim Sat, 05/05/2007 - 23:13

try pinging the other side LAN or serial of the other side router with the source ip of the LAN interface of your router my guess it will not succeed. are you using IPsec/GRE tunneling if so then you might have a problem with the access lists configured on either router. if you could post the configurations of the tunnels on both routers it might help.

manish.shah.neo Sun, 05/06/2007 - 04:05

Thank you but it started working fine, do not really know what happend. BTW how can I ping using with the source ip of the LAN? NO we are not using IPsec/GRE tunneling.

mohammedmahmoud Sun, 05/06/2007 - 04:19


To ping using a soure IP, you should use extended ping:


Protocol [ip]:

Target IP address:

Repeat count [5]:

Datagram size [100]:

Timeout in seconds [2]:

Extended commands [n]: y <---

Source address or interface: fastethernet0/0 <---

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]:

Type escape sequence to abort.

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

Packet sent with a source address of


Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/4 ms

HTH, please rate all helpful replies,

Mohammed Mahmoud.

aeljabari Sun, 05/06/2007 - 04:31

Do one thing more, try to telnet the other end router, and ping your LAN (using the extended ping). if it success that mean you have to review the configuration in your side router and check the access list.

if it fail, i think the problem is on the tunnel. cisco router crached tunnel down. so rebuild your tunnel again.



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