Oracle Linux: Ethernet packets appear to be routed incorrectly when multiple IP addresses/interfaces exist on the same subnet (Doc ID 1276507.1)

Last updated on APRIL 21, 2020

Applies to:

Symptoms

Ethernet packets are not routed correctly when multiple interfaces/IP addresses exist in the same subnet, for example.

Host A has two network interface cards (NICs) each with a static IP address in the same subnet

• eth0: 192.168.0.A1
• eth1: 192.168.0.A2

Host B has two NICs each with static IP addresses in the same subnet:

• eth0: 192.168.0.B1
• eth1: 192.168.0.B2

The following behavior is observed when one server pings the other.

Scenario: host A pings host B with specifiying the NIC ...

1. When unplugging port 2 on host B for the first time, ping to port 2 continues, but those to port 1 stop, then both ping responses continue
2. When unplugging port 1 on host B, all ping responses stop
3. When unplugging port 2 on host B again, ping responses continue

Scenario: host A pings host B specifying the NIC ...

1. When unplugging port 2 on host B for the first time, both ping responses stop and restart - some ICMP packets go missing during this time
2. When unplugging port 1 on host B, both ping responses stop
3. When unplugging port 2 on host B again, ping responses continue

Note that the above behaviour differs to other operating systems e.g. Microsoft Windows where given the same scenario, unplugging one port would result in complete packet loss to the corresponding port.

Changes

The system with two NICs is configured with two IP addresses on the same subnet.

Cause

My Oracle Support provides customers with access to over a million knowledge articles and a vibrant support community of peers and Oracle experts.