[CentOS] Virtual IP

[James Hogarth]

On 6 July 2017 at 15:41, Scott Robbins <scottro11 at gmail.com> wrote:
> On Thu, Jul 06, 2017 at 08:17:17AM -0400, Jonathan Billings wrote:
>> On Thu, Jul 06, 2017 at 11:17:12AM +0300, Amine Tengilimoglu wrote:
>> >    i need your helps on setting the virtual ip. I am trying to setup static
>> > virtual ip on CenOS7.  but I want my VIP to should not open when rebooting.
>>
>> It looks like you're trying to add the second IP on an aliased
>> interface, something that you used to have to do in older releases of
>> CentOS.
>>
>> In C7, you just add multiple IPs to the interface, no need to use
>> eth0:1 style names.
>>
>> In the ifcfg-<device>, you can just put in IPADDR1=1.2.3.4 and
>> NETMASK1=255.255.255.0, and PREFIX1=1.2.3.0.
>>
>> The documentation is in
>> /usr/share/doc/initscripts-9.49.37/sysconfig.txt (part of the
>> initscripts package), which says:
>
> There's a clearer explanation, IMHO, with examples, here.
> https://community.spiceworks.com/topic/545859-add-secondary-ip-to-one-interface-in-centos-7
>
> I don't see mention of it in the RHEL-7 release notes, they just say NM is
> better than it was, and perhaps there's an easy way to do it with NM.
>
> I've left the text that J.Billings kindly included, in below.
>
>
>>
>>
>>   Base items:
>>     NAME=<friendly name for users to see>
>>       Most important for PPP.  Only used in front ends.
>>     DEVICE=<name of physical device (except dynamically-allocated PPP
>>       devices where it is the "logical name")>
>>     IPADDRn=
>>     PREFIXn=
>>       Network prefix.  It is used for all configurations except aliases
>>       and ippp devices.  It takes precedence over NETMASK when both
>>       PREFIX and NETMASK are set.
>>     NETMASKn=
>>       Subnet mask; just useful for aliases and ippp devices.  For all other
>>       configurations, use PREFIX instead.
>>
>>     The "n" is expected to be consecutive positive integers starting from 0.
>>     It can be omitted if there is only one address being configured.
>>
>> So, you can have IPADDR0, IPADDR1, IPADDR2, etc.
>>
>> All of these will configure an IP on the device named in the DEVICE
>> line.  No need to have multiple alias interfaces.
>>
>> --
>> Jonathan Billings <billings at negate.org>


Don't even go near an aliased interface on EL7 ... it's the most
painful way to handle this and not NM compatible.

Here's an article I wrote way back on handling this:

https://www.hogarthuk.com/?q=node/6

Note that with NM in use (as should be the case on EL7) it's as simple
as: nmcli con mod <conn-name> +ipv4.addr "10.0.0.2/24"

https://www.hogarthuk.com/?q=node/8