Turn: Linux dual NIC configuration two IP at the same time there is only one reason

Root cause:

Reverse route checking is enabled by default on Linux

If 2 network cards are inside a LAN, then the server may find the gateway from eth0 or eth1, if a packet from eth0 into the gateway on eth1, then from the eth1 is out of the way, it will not pass. The reverse route check asks where it came from to go back.

Turn off reverse route checking (replace the network card name of the second third row, depending on your situation):

echo 0 >/proc/sys/net/ipv4/conf/all/rp_filter
echo 0 >/proc/sys/net/ipv4/conf/eth0/rp_filter
echo 0 >/proc/sys/net/ipv4/conf/eth1/rp_filter

Each boot automatically turns off the reverse route check, adding/etc/rc.local.

Turn: Linux dual NIC configuration two IP at the same time there is only one reason