DNS round robin

DNS round robin is useful in server load balancing. Access to a domanin name can point to different IP addresses in a cyclic order. This feature is only available in BIND but not in Windows DNS.

CNN is using DNS round robin to group some servers concurrently serving for the domain name "www.cnn.com". The IP addresses returned upon nslookup query are :

64.236.24.4, 64.236.24.12, 64.236.24.20, 64.236.24.28
64.236.16.20,64.236.16.52, 64.236.16.84, 64.236.16.116

CNN has now used up to 8 IP addresses. The maximum no. of IP addresses in DNS round robin for a host is "13". This limitation is due to the 512 byte length in UDP message.