Super-Networking Blog

So I have been doing BGP on Cisco routers for about 6 years or so, it is a really good way of having a redundant ISP connection. Sure it can be a pain to get it setup as some ISPs take a while to get the settings right but once it is setup and tested normally it works like a charm. Typically I run the 2 ISP connections in an active/standby fashion instead of load sharing. This allows you to get a better rate on the backup connection as long as you don’t use them on a regular basis. Not using both connections is easier said then done though, when you setup BGP by default it will choose the best route for the connection so it will use both connections. In the past I have done my best to fix this problem by weighting the connections both in and out so I can choose the best path for outgoing connections and advertise the best path for incoming connections. Doing it in this manner works pretty well but their is always some traffic on the incoming side of the redudnant ISP for destinations that are directly connected to that ISP.

I have never had a problem with this lower amount of traffic before from that 2nd ISP but I was tasked recently with finding a way to bring that traffic down to almost zero. What I found was BGP Conditional Advertisement Feature that Cisco has. I had never heard of this before but sounds like the perfect solution to my problem. Basically what this feature does is allow you to setup a conditional BGP advertisement to the 2nd ISP connection. In this condition you put a route or some other dynamic information you recieve from ISP 1 and your normal advertisments for ISP 2. If this condition sees the information you specified from ISP 1 it will withhold the advertisements from ISP 2. If the information from ISP 1 goes away the condition will then advertise to ISP 2. I have not put this in place yet as I am still looking into aspects of putting it in place. This might cause a longer outage when ISP 1 fails but will solve the problem of incoming traffic on ISP 2 because if I am not advertising at all out ISP 2 I can’t get any traffic from them.

Here is a document on how to configure this feature on you Cisco Router.

http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a0080094309.shtml

I really need to start blogging again. I have stopped tweeting because I couldn’t put enough content in a status update and have moved to facebook but still not the same thing. Stopped blogging when I made it all about optimizing my posts and visibility on the Net. This made it way to time consuming and didn’t see the point in continuing. Will try to start up again, I find that this blog is a nice archive of the projects I have done. When I come across something that I know I have done in the past I can simply search my own blog to find the answer instead of racking my brain for all the little details.

Here is to Happy Blogging in 2011