I am trying to find out if there are any advantages to having a static IP addresses. I find many references to if I should have one for a home interenet connection, but for hosting a web/mail server, I did not really find anything. I will be setting up my own DNS with ISPConfig, so I need at least 2. But, what are other reasons static IPs would be useful? I've heard that one IP per domain can be useful. But, that is the only example. Thanks for any feedback. Joseph
Static IP is useful in some instances, but there are uses where IP that changes occasionally is not a problem. If all connections on a host are outgoing, it does not matter much if the IP is different from what it was yesterday. When users in the Interwebs need to connect to a server, it is a problem if the IP of that server changes. The users workstation needs the IP-number to connect, hostname and such are just to help humans. The workstation needs to discover that IP-number from somewhere, and that somewhere can try to keep the information updated, but in practise there are delays in updates. For example DNS name service may need from 4 to 48 hours to update an entry. So users would not know how to connect to a server for 4 to 48 hours, and this would upset the servers owner somewhat. Summary: if connections are outgoing, static IP is not needed miuch if connections are incoming, having a static IP helps a lot
that was more for before webservers supported SNI, so if you wanted a certificate on a website you needed a dedicated ip to apply that certificate to, now you can apply multiple certificates to various sites all using the same ip. as @Taleman stated, the main benefit of static ip's is knowing exactly what ip any particular server is on now, was on previously and will be on in the next minute/hour/day/week/month unless manually changed by the server owner. in your case, you can stlll use dhcp, and a dynamic dns service. you just need to be aware that there can be some delay between the ip address changing and the dns changing, and even more between the dns changing and any dns caches updating. if you're configuring some software to connect directly to a particular ip rather than using dns or hosts files, as some do, simply to eliminate the time required to lookup the ip for the hostname/fqdn, then a static ip on the target server is essential.
For any server, we always have to use static IP for stability in connection but this, however, does not mean that the public ip for the same server need to be static though, except when consistency is needed for reliability like a dns server or certain ports are needed to be always opened like port 25 for a mail server which might be closed for some dynamic ips. Also, one will always have to differentiate, for example, between a server behind a nat with a vps server, in order to understand and manipulate the advantages of having (or avoiding the disadvantages of not having) the static ip. For instance, in a local network environment, you simply might want the access from one server to another be limited only to certain local ip and never via public ip; similarly, you might want to limit access to certain remote server(s) to a particular ip; thuswise, static ip may also become necessary for a good security practise.
A static IP is important if you are operating a mail server, because most black list work on an IP basis. So there is a reputation per IP. If you change the IP address, you loose your reputation. Additionally, many providers don't accept (or move to spam folder) mails from non-static IP ranges.
Static IPs matter if the services (mail server for example) using said IP can't change. Your mail server would go down if your IP dynamically changes to something else and you don't update your A record.
