While configuring your routing (like load balancing with dual ADSL connections) you would often need to view the current route cache and also to occasionally delete the current cache. Here is how you can do it.

When Google Checkout came out I was very excited to have a viable alternative to PayPal from a reputed company despite its limitation to US only market. Since its launch I have heard several complaints from my readers, with zero positive experiences.

In many location, including but definitely not limited to India, single ADSL / Cable connections can be unreliable and also may not provide sufficient bandwidth for your purposes. One way to increase reliability and bandwidth of your internet connection is to distribute the load (load balancing) using multiple connections. It is also imperative to have transparent fail-over so routes are automatically adjusted depending on the availability of the connections. With load balancing and fail-over you can have reliable connectivity over two or more unreliable broadband connections (like BSNL or Tata Indicom in India). I present you with the simplest solution to a complex problem with live examples. Note: Load balancing doesn't increase connection speed for a single connection. Its benefits are realized over multiple connections like in an office environment. The benefits of fail-over are however realized even in a single user environment. The load balancing mechanism, to be discussed with example below, in Linux caches routes and doesn't provide transparent fail-over support. There are two solutions to incorporate transparent fail over - 1. compiling and using a custom Linux kernel with Julian Anastasov's kernel patches for dead gateway detection or 2. user space script to monitor connections and dynamically change routing information. Julian Anastasov's patches have two problems: 1. They work only when the first hop gateway is down. In many cases, including ours, the first hop gateway is the adsl modem cum router which is always up. So we need a more robust solution for our purposes. 2. You have to compile a custom kernel with patches. This is somewhat complex procedure with reasonable chances of screwing up something. It also forces you to re-patch the kernel every time you decide to update your kernel. Overall I wouldn't recommend anyone going for kernel patching route unless that is the only option. Also in that case you should look for a rpm based solution (like livna rpm for nVidia drivers) which does it automatically for you. A better solution is to use a userspace program which monitors your connection and updates routes as necessary. I will provide a script which we use to constantly monitor our connections. It provides transparent fail over support with two ADSL connections. It is fully configurable and can be used for any standard dual ADSL / Cable connections to provide transparent fail over support. It can also be easily modified to use for more than two connections. You can also use it to log uptime / downtime of your connections like we did.

Modern DSL modems by default allows you to establish a DSL link through them to provide internet connectivity. The actual connection is handled by software running on your computer. The downside is that the client side software consumes your precious CPU cycles. Also the internet connectivity of your internal network is now dependent on a particular computer being up all the time. The good news is that most (A)DSL modems can be configured to do much more to make your life easier and solve all the above problems. Modern DSL modems are like a mini-computer. They can act as a router, a gateway with NAT support, Firewall, DHCP server and also as a DSL modem. Once you connect a properly configured ADSL modem to your hub or switch, all your computers will be automatically and transparently connected to the internet with firewall protection.