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):

1. confirm, he can attach IP-KVM to both servers simultaneously
2. 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).
3. 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:

1. order additional IP address 2 for server A
2. order IP-KVM connection to both servers simultaneously for a time of work
3. 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.

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