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I have 3 separate vlans and subnets (192.168.175.0/24,192.168.176.0/24, 192.168.178.0/24). I need to have the ability to print from a single network printer from any server on these subnets. I have created a 4th vlan for this purpose but I'm not really sure how to configure the intervlan routing on the main switch where these vlans are.

I'm using a Cisco 3560G and trying to use the routing wizard.

user3532047
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1 Answers1

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Okay, so... Routing between VLAN's is really very simple. First, a VLAN is nothing more than a broadcast domain. When you try and send a packet to a machine, an ARP broadcast goes out to see if any hosts on the local broadcast domain (VLAN) have the IP address. If so, they respond with the MAC address. When an ARP response isn't received, the packet is sent to the router to do something else with it. If the address is not part of the local broadcast domains network (identified via the subnet mask), it's sent to the networks router.

Take the following in to consideration: You have 4 VLAN's... VLAN1, VLAN2, VLAN3 and VLAN4. Each has their own /24 network: 192.168.1.0/24, 192.168.2.0/24, 192.168.3.0/24 and 192.168.4.0/24 . What you should have on your router is something like this:

(interface names may be different, but you'll get the idea)

int fa0/0 no shut int fa0/0.1 encapsulation dot1q 1 ip address 192.168.1.1 255.255.255.0 int fa0/0.2 encapsulation dot1q 2 ip address 192.168.2.1 255.255.255.0 int fa0/0.3 encapsulation dot1q 3 ip address 192.168.3.1 255.255.255.0 int fa0/0.4 encapsulation dot1q 4 ip address 192.168.4.1 255.255.255.0

The "encapsulation dot1q #" is telling the router, "Encapsulate any L2 frames on this interface with VLAN ID #" . VLAN's are a L2 concept, not L3. So, that in mind, it's important to understand we need to "transport" that L2 connectivity back to the switch and the hosts on the switch.

With the above configuration, interface fa0/0 should be connected to a trunk port on the switch. If you're plugged in to a Cisco switch, "switch port mode trunk" should do the trick. If you're using a non-cisco switch, it will most likely be:

switchport untagged vlan 1 <- default vlan switchport tagged vlan 2,3,4 <- other VLAN's allowed

That in mind, any hosts should be on ports in their respective VLAN:

Again, if cisco: switch access vlan # If not, most likely: untagged vlan #

For each port that has a host.

Each host in each VLAN should have their respective gateways as their default gateway... i.e. VLAN 1 should have the IP of fa0/0.1 (192.168.1.1) . VLAN 2 - fa0/0.2 (192.168.2.1) .

This is a very simple methodology. I'd recommend you grab the CCENT or CCNA library, as it can greatly help you understand these concepts.

Jonny Whatshisface
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