Running Linux, ddclient is highly suggested software for updating DynamicDNS servers. It supports updating a variety of servers. Some of them are dyndns.com opendns.com and no-ip.com. ddclient supplies documentation to update multiple hostnames (on the same server) but does not have an example with multiple servers. Here is an example that covers all those combinations.
## ddclient configuration file daemon=600 # check every 600 seconds syslog=yes # log update msgs to syslog firstname.lastname@example.org # Mail failed updates to user # requires sendmail installed. pid=/var/run/ddclient.pid # record PID in file. ssl=yes #use ssl ## Detect IP with our CheckIP server use=web, web=checkip.dyndns.com/, web-skip='IP Address' protocol=dyndns2, login=user1, password=YOURPASSWORD \ some.selfip.org protocol=dyndns2, login=user2, password=ANOTHERPASS\ someother.selfip.org protocol=dyndns2, server=updates.opendns.com, login=user3, password=psswd3 \ home