RRDNS...

[Barry Margolin]

In article <200003022230.PAA14766 at av.alpa.com>,
Urivan Saaib  <saaib at ciberlinux.net> wrote:
>Some partners and i been working into a project for long as 3 years by
>now, and the time to open the web site to public has come (21 March). We
>have 4 different computers into several networks connected to the
>internet, and we're looking for a solution anti-slash-effect using round
>robin dns.
>
>I'm familiar with the idea, but not implementing the service and what
>benefits or pitfalls can it have once running.

I'm not sure what you're asking for.  What does "anti-slash-effect" mean?

Round-robin DNS just does one thing: if there are multiple records with the
same name and type, the server will return them in a different order each
time it's queried for that name/type.  This is mostly useful with A
records.

Implementing it is simple: just put multiple records in the DNS, e.g.

www  A  10.1.2.3
     A  192.168.8.17
     A  172.18.15.20
     A  192.168.20.30

The main benefit of RR DNS is that it provides a simple way to get load
balancing among the servers.  Most client applications just use the first
address in the list of addresses that's returned, and each time a client
queries the first address in the list will rotate among them.  Some
applications will try multiple addresses if the first one fails, but
usually try them in the order of the addresses in the list returned from
the server.

The pitfalls are assuming that RR DNS can do any more than this.  In
particular, it doesn't provide failover if a server goes down.  As I said
above, most applications just use the first address returned, and the DNS
server doesn't check the health of the web server when determining what to
send in the DNS response.  If you want something like this, you need to use
something other than RR DNS, such as Cisco Distributed Director or lbnamed.

-- 
Barry Margolin, barmar at bbnplanet.com
GTE Internetworking, Powered by BBN, Burlington, MA
*** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
Please DON'T copy followups to me -- I'll assume it wasn't posted to the group.