Linux 变更主IP

本质需求

业务特性：一些Linux主机公网口需配置多IP，特定场景下需切换出口IP并尽量减少网络波动

默认情况下，主（primary）IP会作为出口IP; 从（secondary）IP可以通过ip addr add/del 增减，主IP不可以直接删除

原始（本质）需求并不是更改主IP，而是更改出口IP

1	Note: for every scope (i.e. same net with address/netmask combination) all aliases are deleted, if you delete the first (primary).

解决方式一

翻ip-sysct.txt看到promote_secondaries，测试后通过

sysctl设置promote_secondaries=1，然后可通过ip addr del删除主ip，从IP升级为主IP

promote_secondaries - BOOLEAN
    When a primary IP address is removed from this interface
    promote a corresponding secondary IP address instead of
    removing all the corresponding secondary IP addresses.

解决方式二

通过ip route变更默认路由src不是主IP

例如 11.11.2.253是从IP

ip route change default via 11.11.2.254 dev ens32 src 11.11.2.253