DHCP Address Reservations Help Solve IP-Related Issues

Gordon van Zuiden (gordon@cybermanor.com) is president of cyberManor in Los Gatos, California.

Over the last decade of custom home installations, we have seen an explosion in the number of products that we now connect to a client’s home network. A networked, connected smart TV is now connected to cable boxes, media streamers, and Blu-ray players–all of which have network connections. Wholehouse audio systems, home control systems, and even sprinkler systems, alarm clocks, and pianos can now have network connections.

In my home, we have 48 networkconnected devices. An extremely important networking concern is how a custom integrator can best manage and monitor all of these devices in the home to ensure that they are running properly. First and foremost, every device on a home network needs an IP address to communicate with other devices on the network and the internet. These IP addresses are typically private IP addresses assigned by the home’s router as either a static address, which needs to be manually assigned to a device; or a dynamic address, which is automatically given to a device when it is first powered on.

The Static IP Address

The advantage of a static address is that you always know the address of a device to locate or control it. The challenge of static IP addressing is that it requires the product that receives the static IP address to have software that supports the manual input of a given, static IP address. All office-based network products typically support this direct input of a static IP address, but many networkable home entertainment devices will not allow an input of a static IP address (the Sonos music system or Boxee are examples).

For many products, it may not matter that an IP address changes, but in some cases it does matter. It becomes especially important when we start to apply home networking monitoring solutions from companies like ihiji, where one of the core strengths of their monitoring solution is to let the integrator know if all the devices on the network are on by “pinging” their IP addresses on a regular basis. If a Sonos player reboots and receives a new dynamic IP address that ihiji does not recognize, it will incorrectly diagnose that the Sonos is offline.

DHCP address reservations are an important tool for dealing with a network crowded by IP addresses and the myriad of potential issues that presents.

In a separate issue, we have seen a problem with some of the newer TiVo products that when we assign a static IP address, the TiVo unit still requests a new dynamic address over a period of time. This wreaks havoc on our universal remote control solutions because they do not know that the IP address of the TiVo has changed; therefore, it can no longer be controlled when we use IP as the control communication medium (as opposed to IR).

So what can you do to prevent these changing IP address related issues? Use DHCP address reservations.

Applying DHCP Reservations

DHCP reservations behave just like a static IP address for a given device. Once a product has been assigned a DHCP reservation, it will always receive the same dynamic address.

In the previously mentioned TiVo example, the dynamic address that was assigned to the TiVo by the router can now be paired with its MAC address to ensure that it will always receive the same IP address. The same dynamic address pairing can be done for the Sonos systems and all of the other dynamically addressed networked products in the home. This level of network address housekeeping ensures that we can monitor and manage the IP devices in the home because they will always receive the same IP address.

Not all routers support dynamic IP address reservation, but it is my recommendation that you only install router models that do support this feature. To enhance the reliability of the residential home networks that we install and improve our ability to troubleshoot and maintain them, it is imperative that the IP addresses of the home’s network devices remain fixed and stable. DHCP IP address reservations are one of the best tools that we can implement to keep our clients’ home networks running smoothly and trouble-free.