Round Robin

Mark_Andrews at Mark_Andrews at
Thu Nov 25 23:28:33 UTC 1999

	The long term solution to this is to write a draft stating
	how to use SVR records with FTP.  SVR records are ideally
	suited for this situation.

	The trick below will work though it does consume address

	You can also create 11 CNAME records for ftp.example 

		ftp.example CNAME ftp1.example
		ftp.example CNAME ftp2.example
		ftp.example CNAME ftp10.example
		ftp.example CNAME ftp11.example

		ftp1.example	A	<main_server>
		ftp10.example	A	<main_server>
		ftp11.example	A	<backup_server>

	If you do this make sure you have an up to date (8.2.2-P5)
	version of BIND for all the servers for this zone.  We
	introduced a bug in the handling of multiple-cnames around
	8.1.2/8.2.  You also need to turn on multiple-cnames in
	the options block for all thse servers.  This solution has
	the drawback that if the ftp client is willing to try all
	the addresses it is given you won't get automaitic failover.
	You can alleviate this bu making ftp1.example have both
	address ftp1 to ftp10 having main_server first and
	backup_server second, ftp11 having the reverse order and
	setting rrset-order for these records (not ftp.example) to
	fixed on all the servers.

	There are also commerial products from the will do this
	sort of thing.  CISCO makes a product as do others.  Go
	to and perform an advanced search in the forum
	comp.protocols.dns.bind where bind-users is gatewayed to
	find other vendors.


> As bind ignores duplicate records
> eg
> dreamer IN A x.x.x.x
> dreamer IN A x.x.x.x
> and thus it is impossible to load balance based on the specs of individual ma
> chines, would 
> proportionally multi homing a machine and thus having many records with diffe
> ring ip 
> addresses to balance it out?
> eg
> machine one, daul athlon 800 2gig ram (main ftp server)
> assign this machine ten ips
> machine two, p200 128 ram (extra server)
> assign this one ip
> then list A records for all ten ips and thus make machine one ten times more 
> frequently 
> accessed than machine two.
> Is this a viable trick or is there a better way to implement load balancing?
> cheers
> --
> Marek Narkiewicz, Webmaster Intercreations
> Reply to <-marek @ intercreations . com->
> "Ticking away, the moments that make up a dull day"
> Pink Floyd
> Time
Mark Andrews, Internet Engines Inc. / Internet Software Consortium
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark_Andrews at

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