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Reverse Telnet Problems

When I'm working on a router (let's say a 2600 Series) that I have accessed using reverse telnet from another router, I've come upon a problem. Normally, when a traceroute is "going nowhere", you have to hit the escape sequence, "control-shift-6" to break the traceroute and return to the command prompt. However, I can't seem to do that during reverse telnet. The sequence has no effect, and then if I hit the "x" key, it throws me back into the router I started from. If I reverse telnet again, the traceroute is still going on. I can't figure out how to stop it. Is this just a problem with my terminal emulation program (Procomm)? Is there any workaround.

Here's a related problem: sometimes I have to telnet from a local router into a remote router, and then reverse telnet from that router into a third router. Whenever I hit the escape sequence, I always get thrown back into the local router..and if I type "resume" I get back into the third router again. How can I back out into the remote router I reverse telnetted from? Typing "exit" doesn't do it, because I'm in a console session and "exit" just closes the privileged session and puts me back into user exec. How can I back out one router instead of two. Is that too confusing?

1 ACCEPTED SOLUTION

Accepted Solutions
Bronze

Re: Reverse Telnet Problems

Try 66x.

The first 6 will be interpreted by the router closest to you; the next by the router one away from you, etc.

6 REPLIES
Bronze

Re: Reverse Telnet Problems

Try 66x.

The first 6 will be interpreted by the router closest to you; the next by the router one away from you, etc.

New Member

Re: Reverse Telnet Problems

Thanks, it worked...but how about the first part of my question...how do I break the traceroute?

Bronze

Re: Reverse Telnet Problems

You can only escape out of the traceroute when you are telneted only to that device; the escape sequence will always be understood by one of the devices before the end unit. So if you have A--B--C, 6x will be interpreted by A; 66x by B; 666x by A again, etc. The 6 is required at C to terminate the traceroute, yet the other devices will act on the escape sequence prior to C. So you only option is to escape back to B, terminate the telnet session on C, and reconnect. Or, a less flexible approach is to give each device their own unique escape sequence, but then you would have to remember that.

Bronze

Re: Reverse Telnet Problems

You can only escape out of the traceroute when you are telneted only to that device; the escape sequence will always be understood by one of the devices before the end unit. So if you have A--B--C, 6x will be interpreted by A; 66x by B; 666x by A again, etc. The 6 is required at C to terminate the traceroute, yet the other devices will act on the escape sequence prior to C. So you only option is to escape back to B, terminate the telnet session on C, and reconnect. Or, a less flexible approach is to give each device their own unique escape sequence, but then you would have to remember that.

New Member

Re: Reverse Telnet Problems

Thank you for your response. What if I key in 6 three times before pressing the "x" key. Wouldn't that be understood by the end device and break the traceroute?

Bronze

Re: Reverse Telnet Problems

No, it would be understood by the first device. 6 is the escape sequence; this octet is discarded and the next octet is viewed for a special character, to see what action should be taken. If there is no action to be taken, this octet is passed on and regular processing occurs. And actually, my previous answers were not exactly correct; the question is how many instances of 6 are required to work you way down the chain of connections.

So again if you have RouterA--B--C, then

6 - captured by A, discarded, and the next octet will be reviewed

66 - the first instance is captured by A; the next instance, since it does not require special handling by A, is passed on to B. B will capture this escape sequence, discard it, and wait for the next octet to see what should be done (if anything).

666 - Same as above; however, A parses and discards the first instance; the second instance, since it does not require special handling by A, is passed on to B, and A returns to normal processing on the telnet line. The third instance is once again received by A, discarded, and A waits to see what the next octet.

Following the same thinking, hitting 6666x will get you to the third device, and break out of the traceroute if you are in one.

If there were 4 routers in the chain (A-B-C-D), it would take 8 instances of 6 to send the escape sequence to routerD.

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