VLAN Help

cschaaf

I am going through the CBT Nuggets course and building a Packet Tracer lab along with the videos.

I am on the ICND Part 7: Switch VLANs: Configuring VLANs and VTP, Part 2 video and I hit a snag.

I created some new VLANs and moved a port to VLAN 10. when I do a show vlan command, that port doesn't show up in any VLANs.

If I do a shutdown on that port, then it shows up in VLAN 10. As soon as I issue the no shutdown, it disappears from the show vlan command again.

I can't seem to figure out why.

Any ideas?

Thanks!

ncsugrad2002

Is the port setup as a trunk? Is it being dynamically configured as a trunk by being connected to another switch? If so, hard code to it to be an access port (switchport mode access in interface config mode) and that'll do it.

Trunks do not show up where you're looking and ALL ports are dynamic desirable (they try to become trunks) by default. That is also a huge security no-no, btw.

edit: on second thought, I'm almost certain that is what is happening. try the "switchport mode access" command under the interface in question and it should get rid of the issue. something to be aware of though in the future.

human151

From global config mode:

#int f0/10

---

switchport mode access

---

switchport access vlan 10

trackit

you can also verify that this port is trunk by issuing "show interfaces trunk" command

billscott92787

I set up a simple one switch with one host topology. Here is the output of "show vlan brief"


VLAN Name Status Ports
----

---

---

---

1 default active Fa0/2, Fa0/3, Fa0/4, Fa0/5
Fa0/6, Fa0/7, Fa0/8, Fa0/9
Fa0/10, Fa0/11, Fa0/12, Fa0/13
Fa0/14, Fa0/15, Fa0/16, Fa0/17
Fa0/18, Fa0/19, Fa0/20, Fa0/21
Fa0/22, Fa0/23, Fa0/24
10 VLAN0010 active Fa0/1
1002 fddi-default active
1003 token-ring-default active
1004 fddinet-default active
1005 trnet-default active


As you can see the fa0/1 interface shows up in vlan 10. So, it has to be your configuration. If I place the fa0/1 into trunking mode with the switchport mode trunk command look at the output:


LAN Name Status Ports
----

---

---

---

1 default active Fa0/2, Fa0/3, Fa0/4, Fa0/5
Fa0/6, Fa0/7, Fa0/8, Fa0/9
Fa0/10, Fa0/11, Fa0/12, Fa0/13
Fa0/14, Fa0/15, Fa0/16, Fa0/17
Fa0/18, Fa0/19, Fa0/20, Fa0/21
Fa0/22, Fa0/23, Fa0/24
10 VLAN0010 active
1002 fddi-default active
1003 token-ring-default active
1004 fddinet-default active
1005 trnet-default active


It isn't there anymore. Do what trackit said and check trunking interfaces with the show interface trunk command. If you don't see your interface there past in your running-config to this forum

cschaaf

That was it, I had that port set as a trunk port. when I switched it back to an access port, everything worked as expected.

Thanks for all of the help, everyone!

billscott92787

Congrats on your troubleshooting lol