Ceph installer GUI question

T

tgelser

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Jun 23, 2025
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Hi guys!

Newbie here, so please be gentle :)


In the Ceph installer (Proxmox VE 9, 3 node cluster), when I have to choose the "ceph-public" and "ceph-cluster" network it only let's me choose the local IPs of my configured NICs (I have installed dedicated NICs for ceph-public and ceph-cluster), and not the subnet the NIC is in.
Also editing the entry after choosing is not working.

I was under the impression that Ceph needs the subnet address and not a local IP?

My ceph.conf looks like this:
public_network = 10.10.20.81/24
cluster_network = 10.10.10.81/24

and I believe it should look like this?

public_network = 10.10.20.0/24
cluster_network = 10.10.10.0/24

Can somebody please enlighten me what to do? Should I manually change the addresses in ceph.conf or is this by design?

Thanks in advance for your help!

Tom
 
Yeah, since the CIDR (/24) marks which part of the IP address defines the network, and which the host, it is easy for Ceph to calculate the network part from the configuration.
 
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One more follow up. By having the host part in there as well, it is very clear which subnet is used, when you are not using a /24, but for example a /26.
For example with 10.10.20.81/26 as host IP:
The result would be that the network ID address would be, 10.10.20.64/26 instead of 10.10.20.0 in the /24 case. Yes, one could then of course use the correct network address, but for people not too well versed in subnetting, I think the easiest is to just use the full host IP with CIDR and then we keep confusion (and with that potential misconfigurations) to a minimum. :-)
 
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