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Cisco Router 1600

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by don_pham

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Hi there,
This is one of most interesting problem for me that i would like to share and get some helps from experts. I am very new in Router stuff.
Anyway, We have two networks; one is building 2000 other is 1860 connect two cisco routers 1600 through the 56K line. This has been set up and ran solidly for whole last two years. Now lately it starts having mysterious problem that is it keeps slowing down network traffic or completely drop and come back up itself. But most interesting is when it slow down i ping the router from 2000 building to router 1860 with more than 1000 mil second, but when it 's back to mornal it's around 30 ms. IT does that 4 time a day or more. This is hidden and missed. We had called the Pacbell and tested the circuit but they said it's good. If any of you can guide me a path how to trouble shoot this I am greatly appreciated you very much.
PS: No one did touch or change any configuration on both routers. But it's UP and DOWN just like some one unplug and plug the cable on the back.
Again, Thank you very much for your help.

8 replies

by otl

Circuit may be good, however does PacBell have autotester turned on on their network ? Autotester goes in and tests a circuit both directions, knocking down the circuit with a loopback.

Other possibility is a backup program running, causing congestion on the network?

Possibily re-syncing massive databases?

Always the same time or is it intermittant ?

by charles_j_smith

We definitely need some more information on this one:
1. Did interfaces actually bounce per the logs on either of the routers???? If so please paste the logs in here so we can see them....

2. Run ping tests between both routers using 2000 byte packets and pattern tests 0f 0x0000 and 0x1111, were there any drops??? This is donw via the extended ping prompt..

3. Is the cpu on either of the routers ramping up????? show proc cpu How does the memory look? show mem

4. Is someone nailing an the circuit (causing overutilization)? show int fa0/0 (look for the X/255), what is the value of X???? During the issue???

5. Have you simply tried rebooting all of your equipment on both ends -- including any external csu/dsu (if they apply)??

intermittent troubles are the worst and they are even more worst (can I say that?) if they involve working with a lec - just because they are usually busy and not too willing to help out the little man.

Good luck with it and let us know whatmore information you have so we can help ya out..

Chuck

by curacao_dejavu

Check the version of the firmware also if it doesn't need a upgrade.
Most people forget that sisco routers also have some vulnerabillities and need to be patched too.
Also you could start logging to see what kind of traffic is going through, migh be that something is generating a lot of traffic.

Leopold

by don_pham

On the Show interface, here is result when it's up:

MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, rely 255/255, load 1/255
Encapsulation HDLC, loopback not set, keepalive set (10 sec)
Last input 00:00:00, output 00:00:00, output hang never
Last clearing of "show interface" counters 02:03:31
Input queue: 0/75/0 (size/max/drops); Total output drops: 0
Queueing strategy: weighted fair
Output queue: 0/1000/64/0 (size/max total/threshold/drops)
Conversations 0/83/256 (active/max active/max total)
Reserved Conversations 0/0 (allocated/max allocated)
5 minute input rate 7000 bits/sec, 6 packets/sec
5 minute output rate 2000 bits/sec, 7 packets/sec
23284 packets input, 3109085 bytes, 0 no buffer
Received 869 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
26860 packets output, 1564976 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 output buffer failures, 0 output buffers swapped out
0 carrier transitions
DCD=up DSR=up DTR=up RTS=up CTS=up

I tried to reset both routers. The processor and memory is fine. It still does it. We just have the SBC came and probe the line on site, but they could not see anything wrong of the line.
What else i should try?
Thanks for feed back guys.

by john.four.bells

PS: No one did touch or change any configuration on both routers. But it's UP and DOWN just like some one unplug and plug the cable on the back.

Your PS Statement would suggest the problem lies within the media between the two buildings.

If you can check each section of wire between the two routers especially if you have recently had contractors in, doing office refurbishing or decorating,you may find the problem could be caused by someone having moved the cable and people moving around the offices are occaisionaly coming in contact with the cable and causing the fault.
Also check the PBX distribution boxes if you have had extra lines put in or work carried out in them your modem lines may have been disturbed.

PacBell tested the line ok but if it wasn't disturbed when they tested it it would not show the problem.

Regards
John Smith

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