[lvs-users] netmask for vip?

linbo liao llbgurs at gmail.com
Sat Jun 24 14:19:29 BST 2017


Thanks Julian.

I search the net, all VIP will be removed if primary IP deleted when
promote_secondaries is 0.

Why VIP should not be promoted as primary IP if DIP removed? I try to
search in google, but no luck.

Thanks,
Linbo

2017-06-23 4:25 GMT+08:00 Julian Anastasov <ja at ssi.bg>:

>
>         Hello,
>
> On Thu, 22 Jun 2017, linbo liao wrote:
>
> > Thanks Julian, I  understand /32 for "lo" interface.
> >
> > But my question is VIP for director, it usually configure in other
> > interface than "lo" , what's the difference between /32 and actual subnet
> > of the VIP.
> >
> > In keepalived, if no netmask provide, vip will configure with /32
> netmask,
> > for example:
> >
> > virtual_ipaddress {
> >     192.168.0.111    ; it will use /32 netmask
> >     192.168.0.112/24    ; it will use /24 netmask
> > }
>
>         Not sure about the keepalived specifics but
> in Linux there is no big difference where you configure
> the VIPs on director. The only rules that apply are:
>
> - you should have DIP (Director IP) which is more preferred
> when selecting local address for outgoing traffic, eg.
> add DIP/24 on eth0 before configuring VIP. Such DIP is
> mandatory for TUN mode because we originate IPIP packets
> from DIP.
>
> - In Linux, VIP can be VIP/24:eth0 (same netmask as DIP),
> VIP/32:eth0 or VIP/32:lo, i.e. a secondary address for the
> subnet. For the first case, if DIP is somehow removed,
> /proc/sys/net/ipv4/conf/eth0/promote_secondaries should
> not promote VIP as primary IP in place of the DIP.
>
> - Some setups may want to mix director and real server role,
> in this case they may prefer to put some VIPs on eth0 (VIPs
> used for director role) and to put other VIPs on lo (VIPs
> used for real server role, eg. DR mode). Such separation
> is needed when using eth0/arp_ignore=1 and eth0/arp_announce=2.
>
>         So, in the most of the cases there should not be any
> differences for the above 3 options and the IPVS tools can
> use any of them to configure the VIP on lo or eth0.
>
> Regards
>
> --
> Julian Anastasov <ja at ssi.bg>
>


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