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New Member

ISIS & Low Reliability

Hi ,

I have a 12k router connected via 1 GB Fiber to another which refuses to form ISIS adjancency. The Process gets stuck in the INIT state.

I do however notice the reliability on the interface is like 200/255. We have changed fiber leads,cards on the DWDM equipments and checked the routes to no avail.

Any idea how best i can test an Optical Network from the cisco 12k ? Can it also be related to the operational environments e.g Humidity etc

See interface Status:

GigabitEthernet0/0/0 is up, line protocol is up

Hardware is GigabitEthernet, address is 0016.9d82.e300 (bia 0016.9d82.e300)

Description: *** Link to xxxx ***

Internet address is X.x.x./30

MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec, rely 200/255, load 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Full Duplex, 1000Mbps, link type is force-up, media type is LX

output flow-control is on, input flow-control is on

Carrier delay is 0 msec

ARP type: ARPA, ARP Timeout 04:00:00

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

Last clearing of "show interface" counters never

Queueing strategy: fifo

Output queue 0/40, 0 drops; input queue 0/1500, 0 drops

Available Bandwidth 1000000 kilobits/sec

5 minute input rate 1000 bits/sec, 1 packets/sec

5 minute output rate 1000 bits/sec, 1 packets/sec

26673 packets input, 2644559 bytes, 0 no buffer

Received 0 broadcasts, 0 runts, 11408 giants, 0 throttles

11408 input errors, 0 CRC, 11408 frame, 0 overrun, 0 ignored

0 watchdog, 26383 multicast, 0 pause input

38158 packets output, 19819011 bytes, 0 underruns

Transmitted 0 broadcasts

0 output errors, 0 collisions, 0 interface resets

0 babbles, 0 late collision, 0 deferred

0 lost carrier, 0 no carrier, 0 pause output

0 output buffer failures, 0 output buffers swapped out


Re: ISIS & Low Reliability

In your posted show command you are getting a lot of input errors which are marked as framing errors. This does not tell you a lot other than the data is being corrupted. It does at least point to which fiber of the pair is having issues.

With optical stuff this is most likely due to loss of signal strength someplace in the path. It could also be the interface in the router has issue with not being able to detect the light from the far end.

A couple of things to try.

Verify that you are only seeing errors on one side. If you see input errors on both sides you may have a design issue and be over distance.

First clean all the connection this fixes may of these type issues.

Swap the transmit and receive on both ends. If it is in the fiber path you sould see the input errors move to the other end of the connection.

If the error does not move it is probably the interface in the router.

In the end you may have to borrow or buy a light meter to measure your DB loss in the path.

New Member

Re: ISIS & Low Reliability

Hi Tdrais,

Sorted , your response pointed me to the right direction. had mtu mismatch on different ends of the gig connections, hence the high input errors on one side.

Regularised the mtu & all came fine


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