HA master/slave IPs and public IPv4/30

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HA master/slave IPs and public IPv4/30

Post by SECOIT GmbH » 11 Jan 2019, 22:13

Hi all,
How can I properly set HA addresses on the WAN side if an ISP assigns a IPv4/30 subnet?

For example the network is so that's only one usable address for the customer: - network - provider's gateway / next hop - customer device - broadcast

When using HA I'd use the for the Clavister gateway as shared address. But what addresses can I use for the master/slave private IPs? There's nothing left in the /30 subnet.

Michael Steffens

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Joined: 10 Apr 2008, 14:14
Location: Clavister HQ - Örnsköldsvik

Re: HA master/slave IPs and public IPv4/30

Post by Peter » 15 Jan 2019, 07:51


If you only have one public IP, you simply cannot set any other IP address as the Master_IP and Slave_IP. You can user for instance the LocalHost object that will set an 127.0.x.x address on the Master_IP and Slave_IP.

The need to have 3 public IP's for a cluster is mainly for:

1. Managing the cluster from the internet
2. Sending logs to something on the internet (not recommended)
3. Polling the cluster nodes using SNMP.

Basically anything where you want to connect to the individual cluster nodes from the internet. If there is no need for this at all, there is no need to user 3 public IP's for the cluster. So if you manage the cluster from the local network behind the Firewall, this is most likely not needed at all.

Best regards

P.s. Some may wonder if it's possible to manage the cluster by connecting to the Shared IP and then to end up on the current active node. The base scenario of this does not work, but it is possible to solve using loopbacks. I will probably write an How-To about this when time allows.

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Joined: 19 Jan 2019, 10:51

Re: HA master/slave IPs and public IPv4/30

Post by DexterLas » Yesterday, 13:39

Hi Peter, the principle is the same if you have more than 3 too, right?

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Joined: 16 Apr 2018, 13:50

Re: HA master/slave IPs and public IPv4/30

Post by fras » Yesterday, 13:59

Hi DexterLas,

That is correct, 3 is just the minimum IPs needed.

Best Regards,
Fredrik Å

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