7200 seriers router / line protocol down

Answered Question
Oct 30th, 2009
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I m trying to connect two routers via STM media with pos interface ,but status shows POS up/line interface down .I have checked the media end to end (loop & break ) tested ok .Still line protocol is down & we cant ping to other router .How to resolve or trouble shoot this .Please guide

Correct Answer by marikakis about 7 years 6 months ago

It could be an issue of encapsulation mismatch (e.g. one side uses PPP and the other HDLC). Sometimes there could be issues with the "pos flag s1s0" command (value 0 for SONET, 2 for SDH). Please inform us about the router models and the type of the port adapters/linecards you are using at each side of the link. Posting the pos interface configurations and output from "show controller pos x/y detail" would also help to explore this further.

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Correct Answer
marikakis Fri, 10/30/2009 - 09:03
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It could be an issue of encapsulation mismatch (e.g. one side uses PPP and the other HDLC). Sometimes there could be issues with the "pos flag s1s0" command (value 0 for SONET, 2 for SDH). Please inform us about the router models and the type of the port adapters/linecards you are using at each side of the link. Posting the pos interface configurations and output from "show controller pos x/y detail" would also help to explore this further.

sangee.acm Sat, 10/31/2009 - 01:01
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Dear Sir


I have showd the desired output below .We have checked two router configs ,it is same only .clock source should be different in two routers ?


Is there anything else to check ?Router model is 7200 VXR .Type or port adapter means ? pos oc3 is used .We did loopback line & internal with which protocol comes up .So they say its media problem .But checking with our OF meters media is ok with break & loop condition .Even that loop condition (loop back line from our router )can be seen in distant end router .But the point to note is when the other end give router or physical loop ,we are not getting the status looped in our router as they get when we give router/physical loop .We have been working on it since a week .It will be helpful if u can please guide us




sangee.acm Sat, 10/31/2009 - 01:02
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outputs

ro1#show int pos1/0

POS1/0 is up, line protocol is down

Hardware is Packet over Sonet

Description: connection to trichy

Internet address is 10.15.246.251/29

MTU 4470 bytes, BW 155000 Kbit/sec, DLY 100 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation PPP, LCP Listen, crc 16, loopback not set

Keepalive set (10 sec)

Scramble disabled

Last input 22:02:34, output never, output hang never

Last clearing of "show interface" counters 23:00:20

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: fifo

Output queue: 0/40 (size/max)

5 minute input rate 0 bits/sec, 0 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

496 packets input, 8908 bytes, 0 no buffer

Received 0 broadcasts, 996 runts, 0 giants, 0 throttles

0 parity

125 input errors, 111 CRC, 0 frame, 0 overrun, 0 ignored, 4 abort

16966 packets output, 305368 bytes, 0 underruns

0 output errors, 0 applique, 1648 interface resets

0 output buffer failures, 0 output buffers swapped out

3 carrier transitions


sangee.acm Sat, 10/31/2009 - 01:05
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Dear sir

I cant attach the the other o/p over here since it exceeds the limit .If u can give ur email id i will send it to u

sangee.acm Sat, 10/31/2009 - 03:45
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Dear sir

Thanks a lot for ur guidance & support .I changed the framing from SOnet to sdh ,now everything has come up & router alarm has also gone in both ends & we are both able to ping each other.but now my concern is that the remote end router framing is still configured as SONET ,will that cause any problem ?

marikakis Sat, 10/31/2009 - 04:59
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Sorry for the late response. It seems we are in very different time zones.


The frame type mismatch might be detected by the ADMs causing an alarm to be reported or it might not. Typical configuration is same framing type at both router endpoints, so make sure both sides are configured for the same framing type. That is probably SDH in your case, since changing one side from SONET to SDH cleared your alarm.


Also, configure the clock-source to 'line' at both ends to derive clocking from the SONET/SDH network, which normally has better clock stratum levels than the routers. Otherwise, you might observe some timing errors that affect the quality of your link facility.


If everything goes well, clear the counters of the router interfaces and examine the output of "show controller pos1/0" to monitor the circuit for a while and confirm good status before using it to forward traffic. If there are any issues at this point, contact your circuit provider to resolve them.

sangee.acm Mon, 11/02/2009 - 20:52
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Dear sir


Even with one side SDH itself the network seems to work fine .Is it necessary that we should change configuration in both routers ?Also how can we escalate the o/p of show controller pos ,to know whether everything is going fine ?how to clear counters etc ? can u pls guide on that as well ?

marikakis Wed, 11/04/2009 - 06:26
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What do you mean by "the network seems to work fine"? Are you forwarding real traffic over it?


As I said previously, from my experience it is common to have similar configuration at both sides. Configurations that work with different frame types usually have some type of translation mechanism in the network between the router endpoints. The only way to make sure what the correct configuration is at both sides is to contact your circuit provider. Your routers must be in agreement with the setup of the circuit provider's equipment.


I am not sure what you mean by your suggestion to escalate. This forum is a forum of volunteers. If other volunteers know more about how your issue can be resolved, they can sure post their ideas here without me having to explicitly request it.


I would suggest you posted the output of "show controller pos" here (either in separate messages or you could attach a .txt file with the requested output). You can clear the counters with the command "clear counters pos1/0" for example. Please try to send output from both routers.

marikakis Wed, 11/04/2009 - 08:05
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I forgot to say something earlier. Make sure any loops you have placed at earlier stages of troubleshooting have been removed before issuing pings from any of the routers towards the other.

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