Connect additional switch to existing switch, receiving vlan mismatch, also want to configure same VLAN's

[Charger1129]

Hello! I have a network in with a i have a switch stack configured for voice and data. Particularly, both are configured to pass over the same port.

I want to add a temporary switch (different model) to the network and configure it the same way. In particular, I want to see that I can set up the voice/data VLAN's on this new switch and test to confirm all is working. I need an uplink though back to the original switches so that this new switch can get a proper connection. 

When I connect the new switch in, I can't seem to get an IP and the CLI keeps showing a "Native VLAN mismatch error" and shows the hostname of the original switch. 

So my questions are:

1. How can I add this temporary switch to the existing switch to get a connection, not as another stacked switch?
2. How can I configure the voice/data VLAN's on the switch so as to be able to test the voice/data traffic over the same port? 

[John Blakley]

Have you changed your native vlan to something other than 1 on the "older" switch? If so, the new switch will need to have the native changed on it as well...

[Charger1129]

Hi! Yes I did change the native vlan for that particular port on "Sw2" (New switch) to match "Sw1" (existing switch). The Sw2 port shows native vlan inactive though.

Below is an output from them on that port. 

(SW1)

Name: Gi3/0/5
Switchport: Enabled
Administrative Mode: trunk
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 100 (VLAN0100)
Administrative Native VLAN tagging: enabled
Voice VLAN: 10 (VLAN0010)
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk private VLANs: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL

Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none

SW2

Name: Gi3/0/5
Switchport: Enabled
Administrative Mode: trunk
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 100 (Inactive)
Administrative Native VLAN tagging: enabled
Voice VLAN: 10 (Voice)
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk private VLANs: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL

Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none

[John Blakley]

Did you create vlan 100 on both switches?
 

[Charger1129]

Looks like my Sw2 was missing VLAN 100. I've added that now but I'm having trouble getting the port assigned to the vlan. It's not showing up under any vlan now even though it has the following:

interface GigabitEthernet2/0/42

 switchport trunk encapsulation dot1q
 switchport trunk native vlan 100
 switchport mode trunk
 switchport voice vlan 10
 spanning-tree portfast
end

[John Blakley · Accepted solution]

You don't need a trunk for a voice vlan. You can configure an access port and then add the voice vlan, but depending on the type of phones that you have, this may not work. You can configure one of two ways:

First way:

 switchport mode access
 switchport access vlan 100
 switchport voice vlan 10
 spanning-tree portfast
end

Second way:

switchport trunk encapsulation dot1q
 switchport trunk native vlan 100
 switchport mode trunk
 switchport trunk allowed vlan 10,100
 spanning-tree portfast trunk
end

HTH,

John

*Please rate all helpful posts*

[Charger1129]

Makes sense. But now how about the switch connectivity between ports? Do the ports on each switch need to be configured a particular way in order for the added SW2 to have connectivity in to the network? 

[John Blakley]

Not anything more than normal. Is that what you posted above was the configuration for the uplink? If so, I'd configure it like this just to see if I could get it to work:

switchport mode trunk
switchport trunk native vlan 100

Don't use portfast on switch interconnects even with the trunk command. That's primarily used for end hosts. The above config will allow all vlans over the trunk. The other end should have the same config as this for testing.

[Charger1129]

Looks like all is working! Think I was just missing the allowed VLAN's command on the port. 

My phones are Cisco 7940 IP phones (100mbps) so ideally I think I'd like to do the configurations like you mentioned above: 

 switchport mode access
 switchport access vlan 100
 switchport voice vlan 10
 spanning-tree portfast
end

Another configuration I have from a switch is:

interface FastEthernet3/0/24
 switchport mode access
 switchport voice vlan 10
 spanning-tree portfast

As an example here for my own understanding, I believe in this case "switchport mode access" is using the default VLAN 1, correct? 

[John Blakley]

Yes. If you don't specify the vlan as something other than 1, the default will be 1.

[Charger1129]

Great, thanks again for the help!! Much appreciated!