Need help with a Cisco 4000 series

[AndyHui]

While I may have a little knowledge in some other places, I'm a complete newbie when it comes to networking. Somehow I've been put as network administrator at work.

We have, among other things, a hub connected to our 4000 series backbone. We've replaced the CAT5, but the indicator lights on the hub are out, as is the light for the port in question on the 4000 series. Telnetting into the 4000 series says that the Port is UP, but Line Protocol is down.

Any ideas or pointers on how to troubleshoot this?

 

[spidey07]

Is this a 4000 router or a 4000 switch?

Showing up/down on an ethernet port is awfully strange. Post a copy of "show interface" and I can try to help. Is this truly a 10 megabit hub?

 

[AndyHui]

It's a Catalyst 4006 switch.

Here's the dump:

FastEthernet4/2 is up, line protocol is down
Hardware is Fast Ethernet Port, address is 0002.16c8.6c01 (bia 0002.16c8.6c01)
Description: "20/F HUB console area"
MTU 1500 bytes, BW 10000 Kbit, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Half-duplex, 10Mb/s
ARP type: ARPA, ARP Timeout 04:00:00
Last input never, output never, output hang never
Last clearing of "show interface" counters never
Input queue: 9726727/2000/0/0 (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
110632002 packets input, 120667417 bytes, 0 no buffer
Received 2208593 broadcasts, 0 runts, 0 giants, 0 throttles
82293 input errors, 2010 CRC, 0 frame, 0 overrun, 0 ignored
0 input packets with dribble condition detected
724098752 packets output, 1210085733 bytes, 0 underruns
2545955 output errors, 2079872 collisions, 0 interface resets
0 babbles, 0 late collision, 0 deferred
1 lost carrier, 0 no carrier
0 output buffer failures, 0 output buffers swapped out

 

[HKSturboKID]

Port is UP, but Line Protocol is down.

This is a layer 2 problem. Make sure that all your protocols are in sync.

 

[AndyHui]

Thanks for the pointer. How do I make sure all protocols are in sync?

This connection to a 10Mb hub has been working without problems for over 12 months.

 

[Garion]

Some questions and things to think about..

Have you tried to hard-set the 4006 port to the right speed and duplex, not using auto? It shouldn't change, but you never know..

Try another port on the switch and/or another port on the hub to make sure one of the ports isn't bad. Does your hub have a special uplink port you're using? If so, you're probably using a straight-through cable. If you use any other port on the hub, you'll probably have to switch to a crossover cable.

Unfortunately, hubs DO occasionally die - It's possible that this has happened. It doesn't sound like it's a problem with the 4006, as you either lose the whole switch, the whole blade, or a "chunk" of ports on the blade - It's rare that you lose just one port and still have an up/down. Most "one port is bad" are physically bad - defective connector, etc.

So, I guess the advice is to test each of the componets - 4006 and it's individual port, the hub and it's individual port and the cable. Take each one out of the equation until you figure out what's not working then fix it.


edit: Just noticed that you've got 2545955 output errors. It's not a HUGE number (about .5%) but it's definitely more than you should have. Probably means that you've got a bad cable (or one that's too long).

Ciscos will actually shut a port down if it's they get too many errors, occasionally. have you tried to disable then re-enable the port? If you just do a show port, it should show up as erridsable, or something. It's possible that something else, like Spanning tree might have shut down the port too - This can happen if someone does something dumb like plugging two uplinks from the 4006 into the same hub. I think there's a show spantree, but it really depends on what OS you're running on the switch.

Obviously, I'm way rusty on the details and CLI, but those are the two things that I'd think of. A disable/enabe will clear up most error condition disables. If it disables itself again, look at the hub and unplug everything else into it and try again.

- G

 

[AndyHui]

Thanks very much for the great, detailed response, Garion.

There's no problem with the hub. We replaced the line (straight) but it still wasn't working with the 4006... we put it on another port and it was fine. It's the only port which is out on the 4006. I'll try your suggestion of downing the port and re-enabling it.

 

[spidey07]

port on the 4000 might be bad, but that's rare - usually a whole controller chip will go out and 8-12 ports will have problems.

The number of errors is pretty high. Try clearing the counters, hard setting to 10/half and enabling/re-enabling the port as Garion suggested. He is "da man" you know.

spidey

 

[eliteorange]

what does your configs look like?

 

[nightowl]

Well, the port is already set to 10/Half. I would try plugging a PC into the port on the switch to see if you can at least get Layer 1 & 2 connectivity. I would then do the same with the hub port. Also, on the hub is there a MDI/MDIX switch? This would be used to change a port so that you can use a regular Cat5 cable to connect a hub and a switch together in your case. Maybe this switch was flipped by accident. Also try the following command without the quotes, "show controllers ethernet-controllers f4/2". It will give you a more detailed over view of the port with all of the error listed seperately.

 

[AndyHui]

Thanks everyone. I've temporarily plugged the hub into a different port and it works with no problems. I'll see if I can down the port and bring it back up and see what happens.