03-01-2005 09:42 PM - edited 03-02-2019 09:57 PM
Dear sir,
I am getting serial is up line protocol down(looped) on leased line of 64 k on 1700 series router, when looped from DOT end. Can anybody tell me, what does this mean.
Pleae help.
Regards,
Ashu
03-01-2005 09:50 PM
That would be normal for a loop with PPP encapsulation.
If using HDLC you should get line up, protocol up (looped).
03-02-2005 02:08 AM
The above post by dgahm is correct.
The line protocol on an interface configured with PPP comes up only when all LCP and NCP sessions are negotiated successfully.
LCP keepalive packet option called "Magic number" is greatly useful in determining loops.
When LCP keepalive packets with same magic number is received by the router, the router then knows there is a loop. When it repeatedly get the same magic number in every consequent LCP packet, then it marks the interface as
Hence LCP will not be established and hence line protocol will be down.
03-03-2005 04:18 AM
Thank you very much sir,
Ashu
03-06-2005 12:13 AM
Hi Ashu,
If you do think that the answer clarifies your doubt, do VOTE as this not only identifies correct solution to your problems but also motivates others to give you and others prompt and precise answers.
Best Regards.
03-01-2005 09:53 PM
I faced a similar kinda issue.
All local, remote loops were successful. The problem was found at the remote exchange modem settings.
-Sai.
03-01-2005 10:24 PM
As far as what I have seen, we get line protocol up when looped at DOT end. LP down shouldn't happen.
What encap are you using on LL? default HDLC or PPP.
03-01-2005 10:44 PM
we are using PPP, are you getting a line protocol UP when you give a remote loop to your router?
-Sai.
03-01-2005 10:49 PM
Ashu,
The sequence number in the keepalive packet changes to a random number when a loop is first detected in the circuit. If the same random number is returned over the line, a loop is confirmed.
You could take these steps highlighted here to find out what the problem is:
1. Use the write terminal privileged EXEC command to display any instances of the loopback command. If the router has been configured with this command, enter the no loopback command to remove the loop.
2. Check to see whether the DSU/CSU is configured in manual loopback mode. If it is, disable manual loopback.
3. Reset the DSU/CSU.
These and other troubleshooting steps for the 1700 series are available here http://www.cisco.com/en/US/products/hw/routers/ps221/products_configuration_guide_chapter09186a008007cd3d.html#31068
Cheers,
Josef.
03-07-2005 07:50 PM
It means a loop exist. You are getting the down(looped)
because your interface is most likely configured with the "down-when-looped" statement.
Discover and save your favorite ideas. Come back to expert answers, step-by-step guides, recent topics, and more.
New here? Get started with these tips. How to use Community New member guide