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Community Member

Serial link trouble

Dear Friends,

I have a numbers of serial links. I am using 3700,2600 and 1941 series router.Recently I am experienced a trouble in my 3700 and 1941 series router. Problem is as belows:

The seral link goes off . It shows that the serial is up but the line protocol is down.The e1 controller is alwas up.For testing link, I set the local loopback and found that teh link is still down. After some time , the link gets up autometically. Please see the sh interface result before and after loop back. Please help as soon as possible and feel free to querey.

Yours,

bikash

=========================================

Serial0/2:0 is up, line protocol is down

Hardware is GT96K Serial

Description: XXXX LINK

Internet address is 172.16.254.50/30

MTU 1500 bytes, BW 1984 Kbit, DLY 20000 usec,

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

Encapsulation PPP, LCP Listen

Closed: CDPCP, PPPMUXCP, IPCP, loopback not set

Last input 00:00:08, output 00:00:06, output hang never

Last clearing of "show interface" counters 7w6d

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 51

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

1075084 packets input, 330059814 bytes, 0 no buffer

Received 0 broadcasts, 228 runts, 0 giants, 0 throttles

739213 input errors, 739207 CRC, 149247 frame, 33546 overrun, 0 ignored, 16

3867 abort

4738928 packets output, 219644729 bytes, 0 underruns

0 output errors, 0 collisions, 7454 interface resets

0 output buffer failures, 0 output buffers swapped out

4351 carrier transitions

Timeslot(s) Used:1-31, SCC: 2, Transmitter delay is 0 flags

AAAAAA#conf t

Enter configuration commands, one per line. End with CNTL/Z.

AAAAAA(config)#inter Serial0/2:0

AAAAAA(config-if)#loop

AAAAAA(config-if)#loopback ?

<cr>

AAAAAA(config-if)#loopback

AAAAAA(config-if)#do sh inter Serial0/2:0

Serial0/2:0 is up, line protocol is down

Hardware is GT96K Serial

Description: XXXX LINK

Internet address is 172.16.254.50/30

MTU 1500 bytes, BW 1984 Kbit, DLY 20000 usec,

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

Encapsulation PPP, LCP Listen

Closed: CDPCP, PPPMUXCP, IPCP, loopback set

Last input 00:00:19, output 00:00:11, output hang never

Last clearing of "show interface" counters 7w6d

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 51

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

1075095 packets input, 330059968 bytes, 0 no buffer

Received 0 broadcasts, 228 runts, 0 giants, 0 throttles

739221 input errors, 739215 CRC, 149248 frame, 33546 overrun, 0 ignored, 16

3868 abort

4738956 packets output, 219645113 bytes, 0 underruns

0 output errors, 0 collisions, 7458 interface resets

0 output buffer failures, 0 output buffers swapped out

4351 carrier transitions

Timeslot(s) Used:1-31, SCC: 2, Transmitter delay is 0 flags

3 REPLIES

Re: Serial link trouble

Hello,

looking at your output, there seems to be a physical problem with either your cabling, the modem attached to your serial interface, or the interface(s) themselves. The high number of input errors, CRC, frame, and overrun errors point to such a phyiscal problem. If possible, try and replace the cable, switch to another interface, or have your ISP run a loopback test to the modem (which they should be able to do).

HTH,

GNT

Community Member

Re: Serial link trouble

Dear GNT,

I have no modem.Microwave transmission link exists between the two E1 card of two routers. Four diffrenet routers are showing these type of phenomena . Interesting thing is that the trouble is corrected by itself after some time.

Re: Serial link trouble

Hi Bikash

From my personal experience with RF/Microwave links better check the reliability of the link with the help of the vendor whoever is maintaining the link.

Your provider may have the required tools to check the reliability and set the same on error free frequency too if he finds some drops or interference with the current frequency.

regds

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