At the time of request to the DNS Server in order to resolve domain names, it provides different cnames in one order. It redirects the request to servers which are in groups. The BIND feature of DNS resolveing the domain to the server, the request are sent to the same server.
In case of Multiple CNames, when there are four dedicated web servers clusters configured with a IP address, adding them to the DNS with A names. The srv can be set as per our selectionand should meet up the next option.
srv1 IN A xx.xx.xx.1
srv2 IN A xx.xx.xx.2
srv3 IN A xx.xx.xx.3
srv4 IN A xx.xx.xx.4
Add cnames to resolve www.domain.com to one of servers such as
IN CNAME srv2.domain.com.
IN CNAME srv3.domain.com.
IN CNAME srv4.domain.com.
DNS Dedicated Server will then resolve to www.domain.com. The request is sent over group of servers.
Also, the request that is sent to the domain without www should be forwarded to www.domain.com. In order to avoid cname error, we need to do the following :
options {
multiple-cnames yes;
};
In case of Multiple A records for one domain is thus not appropriate DNS server for BIND 9. We use the following :
www.domain.com. 60 IN A xx.xx.xx.1
www.domain.com. 60 IN A xx.xx.xx.2
www.domain.com. 60 IN A xx.xx.xx.3
www.domain.com. 60 IN A xx.xx.xx.4
In this case, if any DNS load balancing dedicated dedicated server, it will have no idea if the server is down. It does not check the port of the dedicated server. IP can be cached by nameserver, the request cannot be sent to load balancing DNS server.
Round Robin DNS load balancing does have many drawbacks but can removed by using Perl scripts.
