Setting up port duplex

[jahanzeb.feroze]

I am trying to set up the speed duplex as "full", but the port not allowing me this operation, showing the error of unrecognized command, however beside this port, all the other ports on same switch are accepting the command.

Note: Cross cable is connected to this port.

Please suggest

[Charles Hill]

What type of switch?

What version/ios?

I assume you are trying,

conf t

int g0/1

duplex full

[jahanzeb.feroze]

Dear cehil,

Its Cisco 2960
 

[Charles Hill]

Hello Jahanzeb,

Which port is not accepting the command?

Can you copy and paste the interface configuration?

Below is the link to the 2960 configuration guide.

http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst2960/software/release/12-2_55_se/configuration/guide/scg_2960.pdf

[jahanzeb.feroze]

Its gigabit port.

Configuration:

int gig 0/24

duplex full

"unrecognized command"  this error is being shown.

While on rest of the ports it is working, on offending port cross cable is connected, while on rest of the ports straight is connected

[jahanzeb.feroze]

Yes, i am trying the same command, but it is giving error of unrecognized command, but on other ports of same switch, command is working properly.

Note: On rest of the ports straight cable is connected, while on this offending port cross cable is connected

[josoneal]

Hello jahanzeb.feroze,

Can you give us a little more information about your setup?

What model and what IOS version are the connected devices? 

Is the offending interface a Gigabit port or is it a Fast Ethernet port?

You may also want to double check your cable. If there is a cabling issue, look at the CRC counter under #show interface [offending interface]. If the CRC counter is going up then there is most likely a layer 1 issue.

[jahanzeb.feroze]

Its Cisco 2960, connected to another 2960 with the cross cable

Its a gigabit port

CRC are not increasing

Please suggest

[Charles Hill · Accepted solution]

The reason its a gig port.  Gig ports on the 2960 only operate at 1000Mb/s.

Info below came from the 2960 config guide.

"You cannot configure half-duplex mode for interfaces operating at 1000 Mb/s. "

[jahanzeb.feroze]

Dear Its already half duplex, i want it to be full duplex

[josoneal]

Can I have you display the #show interface [offending interface] output onto the forum?

[jahanzeb.feroze]

Sure, i will give you its display, it not showing any error, it is just not accepting the command, while the rest of ports are accepting without any issues

[Charles Hill]

How is the port configured on the other side of the link in question, that is seeing the half duplex.

Both sides of a link need to be configured the same.

Since the 2960 switchport should be full duplex by default, verify the other end of that link is hard coded to duplex full.

If there is a speed/duplex mismatch, it will normally negotiate at half duplex.

[jahanzeb.feroze]

Duplex is set to full on the other end, to make this end same, i want this also to be full, but it is not accepting the command?

What should i do?

show interface [offending interface] output  is shown below

GigabitEthernet0/24 is up, line protocol is up (connected)
  Hardware is Gigabit Ethernet, address is 0021.565b.9798 (bia 0021.565b.9798)
  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive not set
  Half-duplex, 100Mb/s, link type is auto, 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 00:00:00, output 00:00:14, 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 2000 bits/sec, 5 packets/sec
  5 minute output rate 1000 bits/sec, 3 packets/sec
     8532345 packets input, 685285873 bytes, 0 no buffer
     Received 6122657 broadcasts (0 multicasts)
     0 runts, 0 giants, 0 throttles
     244 input errors, 113 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 5923756 multicast, 0 pause input
     0 input packets with dribble condition detected
     1215095 packets output, 147874876 bytes, 0 underruns
     0 output errors, 65 collisions, 1 interface resets
     0 babbles, 23 late collision, 0 deferred
     0 lost carrier, 0 no carrier, 0 PAUSE output
     0 output buffer failures, 0 output buffers swapped out

[jahanzeb.feroze]

Correction, one end is of 4500 (full duplex), while other end is 2960 (half duplex).

Want to change 2960 half duplex to full, but it is saying unrecognized command.