[lvs-users] broadcast address for VIP

Julian Anastasov ja at ssi.bg
Sun Dec 25 10:52:52 GMT 2016


On Sun, 25 Dec 2016, linbo liao wrote:

> I saw most of example will configure broadcast address for VIP, and
> broadcast address is same as VIP.  Like VS-DRouting
> <http://www.linuxvirtualserver.org/VS-DRouting.html>.
> Refer to netmask for VIP
> <http://www.austintek.com/LVS/LVS-HOWTO/HOWTO/LVS-HOWTO.ipvsadm.html#netmask_for_VIP>,
> netmask should be But for broadcast , I can't figure out
> the reason, why should set broadcast same as vip address explicitly ?

	Do not provide broadcast address when configuring VIP.
As VIP is part from some subnet, the broadcast addresses are
automatically generated by the kernel when the primary (first)
IP in subnet was added, see fib_add_ifaddr() for reference.
VIPs should be configured with /32 ( netmask),
so no broadcast is created for them, for example:

1. add RIP/24 on eth0 (first and last address are created as broadcasts)
2. add VIP/32 on lo (for real server) or on eth0 (for director)


Julian Anastasov <ja at ssi.bg>

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