Duplex problems on Catalyst 2960

[zach.koncir]

I'm running into a very confusing duplex issue that I just can't figure out.

At one of my sites, I have a 100mbit TLS. For this connection to work properly, the port on my end needs to be setup for 100mbit, full duplex. When I connect the TLS to an interface on my Cisco 2821, configured at 100/full, it works perfectly. Now the confusing part, I'm trying to connect the TLS to a Catalyst 2960. I configure the necessary port for 100/full, and get 'notconnect' on that interface. I set the interface to auto/auto, and it negotiates at 100/half and causes collisions and packet loss.

I have no access to the ISP's switch at this time.

Anybody know what might cause an issue like this?

[ALIAOF_]

Is that 100 Meg TLS coming into one of those Cieana devices?  And hand off to you is fiber?

[zach.koncir]

TLS hand off is Ethernet. Port is connected to a switch, model unknown, somewhere in the building (which I have no access to).

[m.kafka]

the 100/half is the recommended result for autoconfigured 100Mbit/s ports which can't complete the negotiation

notconnected might have several reasons. udld, some port security settings, err-disable settings

what's the show interface, sh errdisable, sh interface transc properties etc...

[zach.koncir]

Well I'm going to rule out port security right away because it works at 100/half. Same goes for udld.

Why would I be able to force a router interface to 100/full, but not a switchport?

Here's the switch autoconfiguring 100/half:

Switch#sh int Gi0/4

GigabitEthernet0/4 is up, line protocol is up (connected)

  Hardware is Gigabit Ethernet, address is 64ae.0cb9.f084 (bia 64ae.0cb9.f084)

  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

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

  Encapsulation ARPA, loopback not set

  Keepalive set (10 sec)

  Half-duplex, 100Mb/s, media type is 10/100/1000BaseTX

  input flow-control is off, output flow-control is unsupported

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

  Last input 00:00:04, output 00:00:05, output hang never

  Last clearing of "show interface" counters never

  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 192000 bits/sec, 31 packets/sec

  5 minute output rate 49000 bits/sec, 20 packets/sec

     12073490 packets input, 7649871485 bytes, 0 no buffer

     Received 397983 broadcasts (27912 multicasts)

     0 runts, 0 giants, 0 throttles

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

     0 watchdog, 27912 multicast, 0 pause input

     0 input packets with dribble condition detected

     12190225 packets output, 9134113547 bytes, 0 underruns

     0 output errors, 54848 collisions, 1 interface resets

     0 babbles, 88355 late collision, 0 deferred

     0 lost carrier, 0 no carrier, 0 PAUSE output

     0 output buffer failures, 0 output buffers swapped out

Now forced to 100/full:

Switch#sh int Gi0/4

GigabitEthernet0/4 is down, line protocol is down (notconnect)

  Hardware is Gigabit Ethernet, address is 64ae.0cb9.f084 (bia 64ae.0cb9.f084)

  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

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

  Encapsulation ARPA, loopback not set

  Keepalive set (10 sec)

  Full-duplex, 100Mb/s, media type is 10/100/1000BaseTX

  input flow-control is off, output flow-control is unsupported

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

  Last input 00:00:13, output 00:00:17, output hang never

  Last clearing of "show interface" counters never

  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 250000 bits/sec, 41 packets/sec

  5 minute output rate 26000 bits/sec, 23 packets/sec

     12086279 packets input, 7659696828 bytes, 0 no buffer

     Received 398465 broadcasts (27945 multicasts)

     0 runts, 0 giants, 0 throttles

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

     0 watchdog, 27945 multicast, 0 pause input

     0 input packets with dribble condition detected

     12198220 packets output, 9134974749 bytes, 0 underruns

     0 output errors, 54882 collisions, 1 interface resets

     0 babbles, 88359 late collision, 0 deferred

     0 lost carrier, 0 no carrier, 0 PAUSE output

     0 output buffer failures, 0 output buffers swapped out

[Sebju Varghese]

Does Your TLS device support autonegotiation. Can you try 'speed nonegotiate' on 2960?

[Leo Laohoo]

Same goes for udld.

You have UDLD enabled on a copper port????  Turn it OFF!  You won't get any benefits unless you have fibre optic.

In regards to the 100 Mbps half duplex, try the interface command "speed auto 100".

[Alessio Andreoli]

Hi Zach,
Force the speed to full/100, change cable on your side and issue the speed nonegotiate command below interface config. This should work. By the way, if the collisions increase(issue a clear counters command to reset the value) once you force the duplex parameters , there is a massive possibility that the layer 1 is the problem. Do not keep 100/half because it is a very unstable configuration. Hard coding speed and duplex is a best practise.

Hope this helps
Alessio

Sent from Cisco Technical Support iPad App

[ALIAOF_]

What is the TLS device that Verizon gave you?  It can also be an issue with the firmware.  I encountered something similar but with Fiber.  Found out that the Firmware on the Ciena 311v was way to old to handle the latest IOS on the Cisco switch.

[bharat.rajwanshi]

better if you contact with your TLS ISP as they migh have set 100/half thats why you are negotiating with 100/half too, and once you force set it to 100/Full it will break the connection

call them and ask for their device edge setting and request them to set it to 100/Full

Just guessing, problem may be at TLS ISP edge