How to configure VLAN

[ppmsm]

I have 2 1238s and 2 1544s on our LAN. Our ISP has configured a VLAN on the router at this location,
how do I configure this VLAN on all 4 of these switches?

[Anonymous]

:

Thank you for asking this question in the Support Community.  A very similar question has been answered in a previous post.  Please, review this post and let me know if you have any further questions or additional information that was not answered in it:

Levi 

[ppmsm]

I don’t understand the settings for 802.1q so I get stuck there. For instance I don’t know what interface to use for this or what IP address is needed.

Ken Kruger

[Anonymous]

Ken:

When you get a chance, will you provide me with additional information about your network design and requirements (do not include any sensitive information to your company)?

• What is the topology of the network?  Do you have a network diagram? 
• Do you have multiple VLANs in the network?
  • If you have multiple VLANs, is the ISP's router going to route between the VLANs?

Please, let me know the answers to these questions, and I will be happy to assist you in any way I can.

Levi

[ppmsm]

We have 4 switches: SW1 (1238), SW2 (1238), SW3 (1544) & SW4 (1544). SW2 & SW3 are connected to SW1 and SW4 is connected to SW2. I have a VLAN partially defined on SW3 & SW4 but it is not being used. Our ISP has setup VLAN2 for me as a “guest” VLAN. It is setup to route to the outside and not back to our LAN. I would like to use the web interface to configure this, and I get stuck on what information is needed there.

Here is the configuration our ISP sent me:

ip dhcp pool DHCPPOOL

network 10.1.2.0 255.255.255.0

dns-server 216.234.97.3 216.234.97.2

default-router 10.1.2.254

domain-name ppmchoice.org

interface FastEthernet0/0.2

description Guest VLAN

encapsulation dot1Q 2

ip address 10.1.2.254 255.255.255.0

ip dhcp excluded-address 10.1.2.21 10.1.2.255

[Anonymous]

:

Thank you for replying with the requested information.  Encapsulation 802.1q is used when configuring trunking on a router.  Since the products you listed are switches, you will not need to configure 802.1q encapsulation, or IP addresses on these units, but instead, you only need to configure the port connected to the ISP's router as a trunk port.

To setup a specific switchport as a trunk in the command line interface (CLI), do the following:

SWITCH-NAME# configure terminal

SWITCH-NAME(config)# interface switchport 0/<interface number>

SWITCH-NAME(config-swx 0/x)# switchport mode trunk

Note: It is best practice to configure all ports connecting switches together as trunk ports (with the same configuration steps above).

The following document will guide you through the configuration in the web interface (GUI):  Understanding the Switch Menu in the Web Interface

To make the port a trunk in the GUI, you simply have to change the port's "Membership" to trunk.

Levi

[ppmsm]

The ports connecting the 1238 swithces (SW1 & SW2) are set as trunk ports. I think that was the only way they would work. The 1544 switches do not have a setting for trunk ports.

So if I just define a VLAN on each of these 4 switches then traffic from ports in that VLAN will only go to the router that is configured with that VLAN number?

[Anonymous · Accepted solution]

:

The ports connecting the 1238 switches should be configured as trunk ports, as you mentioned they are.  Also, any ports connecting a 1238 to a 1544, or a 1544 to another 1544 should also be configured as a trunk port.  You can configure the ports on the 1544 switches to be a trunk in the same way you can the 1238 switches.

Yes, if you define the VLAN on all the switches, then assign the appropriate ports on the switches to be in that VLAN, as well as make the port connected to the ISP's router a trunk port, then the ISP's router will determine which VLANs can communicate.

Levi

[ppmsm]

I don’t see anything in the web interface on the 1544s to set the port as trunk ports. Do I have to use CLI to do this?

[Anonymous]

:

Navigate to the following:

Data > Switch > Ports > General Tab > Then choose "Trunk" from the "Membership" dropdown box for the port you want to be a trunk.

I have attached a screenshot.

Levi

[ppmsm]

OK I see it now; it is hidden a bit.

Now I have the port that the router is connected to on the 1544 set as vlan 1. If I change it to trunk is that going to cause any issues?

[Anonymous]

:

Based on the configuration you sent previously of the ISP's router, the ISP's router is already configured with encapsulation 802.1q and a sub-interface with VLAN 2.  Therefore, when you configure the switchport connected to the router to be a trunk, it will still pass the native VLAN (VLAN 1), and then will also allow traffic to pass on VLAN 2.

Levi

[Anonymous]

:

I went ahead and flagged this post as “Assumed Answered.”  If any of the responses on this thread assisted you, please mark them as either Correct or Helpful answers with the applicable buttons.  This will make them visible and help other members of the community find solutions more easily.  If you still need assistance, I would be more than happy to continue working with you on this - just let me know in a reply.

Levi

[ppmsm]

This working now, thanks for the help.

Is there something that describes what the significance is of making a port a 'trunk' port, and what ports should be set that way?