Separate VLAN Routing Network

For the separate VLAN routing network. Each VLAN has a port connected to the router. This means that the router has multiple LAN side ports. In the simplest scenario, there is one port/connection dedicated to the voice VLAN and another port/connection dedicated to the data VLAN.

Separate VLAN Routing network

Switch Requirements

This means that you must have a switch with VLAN capabilities. The switch's ports must be assigned to a voice or data VLAN. Each VLAN is assigned to a network with a unique network address.

Router Requirements

The router must have multiple LAN ports AND each port must be configured to a separate network. Each port is assigned a network address that becomes the Default Gateway for that network. Also each router port should be able to act as a DHCP server for its unique network.

Enterprise class routers have these capabilities and are provided by a host of companies like Cisco, 3Com, Juniper, HP, etc.. The catch is that they are expensive and typically out of reach for a home network or even a SOHO's budget. They typically require an expert level of knowledge to configure that usually requires training of some sort.

A lot of routers can provide traffic management for VoIP protocols and QoS through their web based GUI or command line interface. The traffic management typically deals with outbound traffic. Priority can be given to voice protocols like SIP or to the voice VLAN. The router recognizes the voice traffic and when given the choice between sending out data or voice, it will send the voice first. Each router is different and its capabilities would need to be explored to see how it can manage traffic.

Broadband Routers

Most home broadband routers have a built-in 4 or 8 port switch that when taken "right out of the box" will not have the capabilities to separate the LAN ports into individual networks that would fit the requirements of the Separate VLAN Routing Network.

Aftermarket Router Firmware

There are several aftermarket router firmware upgrades that are both free open source and paid upgrades that can add more capabilities to your router. The result is that your el-cheapo router gets a hit of steroids and provides features normally seen only on expensive enterprise class routers. One of these is DD-WRT which allows you to VLAN the internal switch, assign each port to a VLAN and create individual DHCP servers for each VLAN. Unfortunately, aftermarket router firmware upgrades require a level of expertise and patience to get working correctly.

Advantages

The advantages to a Separate VLAN Routing Network are

  • The voice and data traffic are on separate networks until it reaches the router and WAN link
  • LAN Voice traffic is not affected by data traffic - built-in quality of service
  • The voice network's outgoing traffic can be given priority over the data network on the WAN link
  • Voice traffic protocols like SIP and RTP can be given priority over data traffic on the WAN link

Disadvantages

The disadvantages to a Separate VLAN Routing Network are:

  • It is more complex to set up compared to other networks
  • For each VLAN, the router requires a separate physical Ethernet port
  • The number of LAN ports on the router will limit the number of VLANs
  • Routers can be expensive
  • The WAN link is the bottleneck for traffic
Overall this is a very good solution as it pushes the traffic bottleneck and QoS problems to the router/WAN link. Enterprise class routers have built-in mechanisms to deal with these exact problems and manage the traffic on the WAN link. As a network grows, the number of VLANs will increase and finding a router with many LAN ports becomes expensive and difficult. Typically an enterprise router has 1 WAN port and maybe 2 LAN ports.

Note: Soft IP phones that run as apps on the PC ,such as the Xlite softphone, still reside on the data LAN and will have quality issues as their traffic will be fighting with the data traffic for bandwidth.

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Copyright July 2013 Eugene Blanchard