Leased Lines historically have been used as reliable, resilient internet and site-to-site data connections. The main benefits have been security, reliability, SLAs, private network and flexible speeds. Leased Lines were also known for high installation charges, long installation times, hefty monthly fees and unreasonable contracts. With the advent of cheap ADSL connections, Leased Lines have become as relevant as dinosaurs except for the most demanding businesses, especially when you can bond multiple ADSL lines to get reliable broadband at a fraction of the cost.

Full article (235 words) »

That's about the best you can say about the 8 Mbps plans from Airtel. The starter Combo 1299 plan provides 8 mbps @ only Rs. 1299 per month. If you think that is good, think again. There is a big catch.

Full article (184 words) »

I learned it the hard way. Our gateway machine with firewall (shorewall) has multiple ADSL connections configured with load balancing for more bandwidth and transparent fail-over. Today I faced an unenviable problem where one or other of the ADSL connections were going down sometime after a network restart. It was unique because the ADSL modems (configured as router) were accessible via telnet or ping and displayed perfect connectivity. However I was unable to use them as gateway to connect to a server on the internet. They were working fine before. With our non-trivial setup there were many suspects including the shorewall firewall and iptables (dropping certain packets?), network adapter, routing issue etc.

Full article (265 words) »

Shorewall is an excellent free linux firewall which provides unparalleled level of fine grained control. It not only acts as a firewall and Gateway, it also supports DMZ, IP Masquerading (NAT & SNAT), Proxy ARP and more. In short Shorewall is your one stop solution for complex networking routing needs, flexible & controllable internet connectivity options.

Full article (663 words) »

While comparing broadband packages from Tata Indicom and BSNL Dataone, I came across the revised pricing of another provider with whom I have a love-hate relationship. My last experience with them was ok.

Full article (172 words) »

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.
Full article (1971 words) »

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.

Full article (463 words) »

Autoexec.bat is a legacy file in Windows which is executed every time you start Windows. Commands you want to run with startup of windows, and applicable to all users, are added to autoexec.bat. Let's see how you can do the same with Linux.

Full article (184 words) »

The single biggest difference between Tata Indicom Broadband & BSNL Dataone Broadband is the upload speed. With BSNL your upload speed is limited to 5-7 KBPS. With Tata Indicom Broadband / VSNL your upload speed is limited to 512 KBPS.

Full article (182 words) »

In small businesses you will often have the ADSL broadband and telephone line from the same connection. You may also need to setup an EPABX on the connection to share the phone line. For example we use an EPABX to provide 16 internal connections over two external lines, one of which also has the broadband. Here is how you can easily setup both EPABX and your ADSL connection on the same line.

Full article (175 words) »