SUMMARY: multiple machines for one WWW Server

From: Dirk Boenning (
Date: Fri Jun 28 1996 - 04:59:25 CDT


thanx for quick responses. The easiest solution seems to be the round robin
DNS. Thanx to all responder. The best description cames from Leif Hedstrom
(see above).

CU, Dirk.

>Dirk Boenning writes:
>Cause of availability and the extremly high numbers of parallel =
>to the Webserver I want to spread one Webservice over at least two ultra =

This is traditionally done using what's called DNS round-robin.
Basically you'll configure your DNS with (probably) a CNAME for looking like: 1800 IN CNAME 1800 IN CNAME 1800 IN CNAME

This will give you a reasonable load balancing, but it's not perfect
(since DNS is caching). The number 1800 tells other DNS servers to keep
your entries for half an hour. On average you should be getting pretty
fair distribution, specially if you have lots of customers.

If machine goes down permanently, you just have to change
your DNS server to remove it from DNS RR.

Since you are fortunate to use Solaris2.x, you can even have one of the
other machines take over's IP number with something like this

        ifconfig hme0:1 inet up

(This means will be known on the network as both www1 and www2.
 When www2 is back again, do "ifconfig hme0:1 down" on www1.)

This way, even if people try to go to the broken machine (,
they will get a response. This is important to remember, since even
after you change DNS, it will take time until all caching DNS servers
update their entries. Also remember that Netscape Navigator does it's
own DNS caching.

Now, If you are really tricky, invent your own "protocol", and make
machines "back up" each other automagically (it's been done before...).
So when any of the www machines goes down, one of the other takes on his
lost comrade's duties! :)

I hope this helps.

-- leif
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