Load balancing, setting up 2 IP addresses for the same website...

[Kevin Darcy]

Umar Pirzada wrote:

>Hi
>
>i was just wondering how www.yahoo.com gives 7-8 IP addresses on a
>nslookup query? This does mean that they have some sort of load
>balancing implemented. If a query for www.yahoo.com is from asia it
>goes to another server, if from europe it goes to another....
>
As you'll notice, www.yahoo.com is actually just an alias for 
www.yahoo.akadns.net, i.e. Akamai, which does all of this fancy 
"geographic" load-balancing, using their proprietary, patented 
technology, yadda yadda yadda. Note that the actual load-balancing 
happens behinds the scenes, and the fact that the answer to 
www.yahoo.com has several A records in it doesn't *in*and*of*itself* 
imply that any fancy load-balancing is going on. Anybody can have 
multiple A records associated with a DNS name, and just let it 
randomize, or, for a relatively crude form of load-balancing, could use 
BIND's "sortlist" mechanism to try and split up the load based on the 
source-address ranges of the clients.

>How do they do this? I have a website hosted and i want to do
>something of the same sort. For a start i want to set up my server to
>give services from 2 subnets....i mean to say that i have radio
>connectivity with 2 ISPs. At the moment i have a primary LINK and a
>backup link. what i want to do is utilize both the links at the same
>time and create a load balancing scenario. I hope i am making my point
>clear. I want to set up two LAN cards with differnt IP addresses from
>the 2 ISPs and then somehow create the situation where both are active
>at both times.
>
>What do i do? Plz guide...
>
 From a DNS perspective, you could have multiple A-records associated 
with your site's name, as previously mentioned, with or without 
sortlists. Or you could pay a significant amount of money to put 
together a *true* load-balancing solution.

                                                                         
                                    - Kevin