ping command not working

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Sep 25th, 2007
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i have two routers interconnected(1700 & 2600 series)in lab environment.i cannot ping from each host of one router to the host of another router. when i am running ping command from one host it is giving the following reply:

"Reply from : TTL expires in transit". whereas is the ip address of the serial port on which i am running the ping command.

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paul.matthews Tue, 09/25/2007 - 23:56
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TTL expired means you have a routing loop, and the packets are being passed back and forth between the routers.

Could you add extracts from the config of both routers - the interface configs, any static routes or routing protocol config and a sh ip route? also the output of a ping.

It may be worth double checking for typos - make sure all the interfaces have the address you want on them, and that you are not making a typo in the address of the ping command.


bodhayan2007 Wed, 09/26/2007 - 23:23
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thanks Paul for your suggetion, actually no dynamic routing protocol is working on both of the router (although all of them can be configured) and for the static routing though i am configuring statically still the ping command is not working.


paul.matthews Thu, 09/27/2007 - 00:31
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You can have a routing loop withut a routing protocol.

I'll keep this example simle and use /24s all round.

Router 1:



ip route

Router 2:



ip route

So both routers have a lan, and a default route pointing to each other. Go to a host on the LAN on R1 and trace route to and you will gget responses from R1, R2, R1, R2, R1, until TTL expires.

To help we need to see the config of interfaces on the routers, and the routing table of the routers. A log of the ping will help too. it is best if you copy & paste, as manually typing in will not necessarily copy any typos you have made.

smothuku Wed, 09/26/2007 - 00:12
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Hi ,

TTL expires in transmit in the sense not able to reach the destination Ip and the packet is getting dropped in the middle.

Have you checked the status of serial interface on both ends.

can you paste show interface output and if possible config of the routers.



bodhayan2007 Wed, 09/26/2007 - 23:30
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thanks Satish,

i have configured both the router correctly as per book (both statically and dynamically)but still it is not working. is this a problem of IOS ?

please suggest.


paul.matthews Thu, 09/27/2007 - 00:33
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Almost certainly not A problem like this would be rather well known. Another thought - have you brought all the interfaces up on the routers?

hobbe Thu, 09/27/2007 - 00:36
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It could not bee that you have been playing with the TTL cost value in the routing ?

Example of a static route would be something like: route outside 1

The last digt (the single 1) is the TTL cost to route to that network.

When the TTL cost is drawn and it gets down to 0 then the router will discard the packet and send an icmp ttl expired in transit back to you to let you know.

Another reason could be that it takes to long to send the packet. but that is far fetched and most likely not the case here.

if this above is not the case here.

What does a traceroute say ?


Richard Burts Thu, 09/27/2007 - 03:13
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I am not sure what platform you are using with the statement route outside 1. It looks more like a firewall than an IOS based device which I believe is the focus of the original post.

In any case whether it is IOS or firewall the number that follows the mask in the route statement is not TTL but is distance. Using a distance gives us the ability to configure floating static routes when we configure a distance on the static route other than its default distance. So we can configure a static routes with a distance less attractive than other static routes or less attractive than routes discovered by our dynamic routing protocol. So if a route to some destination is available from some other source then that route is used but if there is no route from another source then the floating static is used. But there is not a way to set the TTL in a static route.




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