h1. How long will be down time when moving IP address

Let's suppose, you need to move all services from one server (_servere A_) to another (_server B_).
IP address for services (IP address 1 further in text) is not changed because you don't want your customers and partners to change their configuration.
Most often this procedure is performed to change hardware.

Prerequisites for hosting provider (need to ask him about technical possibility):
# confirm, he can attach IP-KVM to both servers simultaneously
# confirm, that IP address 1 could be moved by customer between servers and there is no additional help from provider needed (i.e. he didn't statically bound IP address to particular server).
# confirm, that he could assign additional 1 IP address for _server A_.

In case if provider doesn't confirm at least 1 item from above, then  we can't use this method and we'll have to use method described in section [[How long will be down time when moving service to other server without moving IP address]].

To perform the procedure you need:
# order additional IP address 2 for _server A_
# order IP-KVM connection to both servers simultaneously for a time of work
# pay forward to hosting provider for at least 1 month for both servers after work is done (in case if new server has HW failures we might need to return back to old server)

Procedure of work performed is as follows:

1. We add _server B_ to cluster to _server А_
Work time and down time is described in section [[How long will be down time when setting up replication]].

2. We set _IP address 2_ as alias on _server A_
Work time: 1 minute.
Down time: not expected.

3. We set _IP address 3_ on _server B_
Work time: 1 minute.
Down time: not expected.

4. We delete _IP address 1_ from _server А_
Work time: 1 minute.
After this item down time begins.

5. We add _IP address 1_ as main on _server B_
Work time: 1 minute.

6. We flush ARP cache on router (we expect it could be done by performing ping from _server B_)
Work time: 1 minute.
After this item down time ends.

7. Now technically you can decline old _server A_
*Attention!* We recommend you to decline old server after all your originators have paid all invoices for the period while traffic passed through old server.
Otherwise some useful data could be lost on old server which could have helped to solve dispute or understand why there is a difference.

[[Сколько будет простой при переносе IP адреса|Русский перевод]]