Show VLAN not showing port once it is connected

matthewwatkin6537 · 2014-07-02T13:22:17.000Z

When I run show VLAN command it shows I have two ports assigned to my relevant VLAN.

When I connect a cable and then run show VLAN once again, the ports are no listed next to the relevant VLAN.

I am a Cisco novice so please word any response accordingly, thank-you.

matthewwatkin6537 · 2014-07-02T13:33:55.000Z

I have just ruled out port security. When I run ‘show port-security’ command there are no MAC addresses in the system.

nikopka · 2014-07-02T13:42:30.000Z

Are you sure that port is part of that relevant VLAN?

matthewwatkin6537 · 2014-07-02T13:44:33.000Z

Yes -

48 Servers active Gi1/0/5, Gi1/0/6

As soon as I connect a device to this port and run the show VLAN command, this port disappears.

steve-flanigan · 2014-07-02T13:47:04.000Z

I’ll have to check this out when I am around a Cisco switch this afternoon, but in the meantime, are these ports showing up anywhere at all, even the default VLAN 1?

matthewwatkin6537 · 2014-07-02T13:51:16.000Z

As soon as I connect a cable, they do not show up on any of my other VLANs. it is as if the port disappears.

jeremyspencer · 2014-07-02T13:51:30.000Z

Can you post the port config? Could be negotiating a trunk when you plug the device in (IP phones will do this). Also, post the output of the command “show interface g1/0/5 switchport” with the device plugged into that port.

matthewwatkin6537 · 2014-07-02T13:56:22.000Z

GigabitEthernet1/0/6 is up, line protocol is up (connected)

Hardware is Gigabit Ethernet, address is c84c.75d5.3c06 (bia c84c.75d5.3c06)

Description: EMC VNXE Storage

MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,

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

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Full-duplex, 1000Mb/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 33w0d, output 00:00:00, output hang never

Last clearing of “show interface” counters never

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 1934916

Queueing strategy: fifo

Output queue: 0/40 (size/max)

5 minute input rate 4000 bits/sec, 6 packets/sec

5 minute output rate 20000 bits/sec, 13 packets/sec

49609117399 packets input, 67616635762676 bytes, 0 no buffer

Received 1009546 broadcasts (1005591 multicasts)

0 runts, 0 giants, 0 throttles

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

0 watchdog, 1005591 multicast, 0 pause input

0 input packets with dribble condition detected

15740561586 packets output, 10598127922518 bytes, 0 underruns

0 output errors, 0 collisions, 1 interface resets

0 unknown protocol drops

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

jeremyspencer · 2014-07-02T13:57:03.000Z

You forgot the switchport at the end of the command.

The command should be “show int GigabitEthernet1/0/6 switchport”

sergio64573161 · 2014-07-02T14:03:05.000Z

The port could be configured as a trunk.

Do a “show interface trunk” does it appear there? If it is, you need to change the port to access mode for it to show up in the show vlan list.

brianwhelton · 2014-07-02T15:53:54.000Z

Sounds like a trunk, are you server ports teamed?

matthewwatkin6537 · 2014-07-02T16:30:21.000Z

Ports were on a trunk and it was closing the port, I found some assistance and got the issue resolved. Thanks everyone.

danielmott3294 · 2014-07-02T16:33:18.000Z

show int trunk

show int gi1/0/6 switchport

The ports may be set to switchport mode dynamic and negotiating a trunk link which will cause the ports to not appear in a show vlan / show vlan brief command.

As a matter of course I always hard code my ports for access or trunk.