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New Member

1841 and Vlan

I need some help in adding a vlan and having 2 vlans talk to one another.  I already have:

interface FastEthernet0/0
description $ETH-LAN$
ip address 192.168.xxx.xxx 255.255.255.0
no ip route-cache
speed auto
full-duplex
no mop enabled

This already is on vlan 1 although not sure why it does not show it.

I have also ran this command:

1841#vlan database
1841(vlan)#vl
1841(vlan)#vlan 2
VLAN 2 added:
    Name: VLAN0002
1841(vlan)#app
1841(vlan)#apply
APPLY completed.
1841(vlan)#exit
APPLY completed.
Exiting....

Now with vlan 1 and vlan 2 in the database how can I have the two vlans talk to one another?  Do I have to use FastEthernet0/1?  This will be for a network with IP Phones and computers.  Computers will be on vlan 1 and phones will be on vlan 2.

Thanks

  • LAN Switching and Routing
1 ACCEPTED SOLUTION

Accepted Solutions
Cisco Employee

Re: 1841 and Vlan

Hello,

The way you created the VLANs is necessary only if you have a switching module such as HWIC-4ESW installed in your router and you configure its switching ports to communicate in different VLANs. The built-in ports Fa0/0 and Fa0/1 are routed ports, not switched ports, and for routed ports, the configuration is different - you do not create the VLANs and instead, you create so-called subinterfaces and assign those to appropriate VLANs.

You do not need VLANs if you can separate the networks with physically different interfaces on your router. You can simply configure your Fa0/1 to use another IP subnet and connect appropriate devices to appropriate ports. No VLANs are necessary in this case.

On the other hand, if you want to use IP Phones that transfer both voice and PC data on the same wire then you do need VLANs, and the configuration would look like this:

interface FastEthernet 0/0.2

encapsulation dot1q 2

ip address 192.168.xxx.xxx 255.255.255.0

The interface Fa0/0 stands for VLAN1 and this so-called subinterface stands for VLAN2 thanks to the command encapsulation dot1q 2.

Please understand that this is a quick-and-dirty guide to configure what you need but there is probably more to learn about VLANs before deploying them.

Best regards,

Peter

2 REPLIES
Cisco Employee

Re: 1841 and Vlan

Hello,

The way you created the VLANs is necessary only if you have a switching module such as HWIC-4ESW installed in your router and you configure its switching ports to communicate in different VLANs. The built-in ports Fa0/0 and Fa0/1 are routed ports, not switched ports, and for routed ports, the configuration is different - you do not create the VLANs and instead, you create so-called subinterfaces and assign those to appropriate VLANs.

You do not need VLANs if you can separate the networks with physically different interfaces on your router. You can simply configure your Fa0/1 to use another IP subnet and connect appropriate devices to appropriate ports. No VLANs are necessary in this case.

On the other hand, if you want to use IP Phones that transfer both voice and PC data on the same wire then you do need VLANs, and the configuration would look like this:

interface FastEthernet 0/0.2

encapsulation dot1q 2

ip address 192.168.xxx.xxx 255.255.255.0

The interface Fa0/0 stands for VLAN1 and this so-called subinterface stands for VLAN2 thanks to the command encapsulation dot1q 2.

Please understand that this is a quick-and-dirty guide to configure what you need but there is probably more to learn about VLANs before deploying them.

Best regards,

Peter

New Member

Re: 1841 and Vlan

Thanks that was what I was looking for.

If your talking about vlan priority and which packet goes to which vlan, I have the switches doing that.

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