Do not connect both Ethernet interfaces on a dual port board, such as a TI EVM into the same switch or router. This does not provide a redundant link. Each Ethernet interface must have an exclusive subnet.

To explain why this network topology fails, assume two interfaces on the DUT are named eth0 and eth1 and are both connected to the same switch. When a ping command (issuing an ICMP request) is initiated from eth1 (ping <Ipv4 address> -I eth1), the packet that is sent out by the DUT is received by the destination platform. To respond to the ping request, the destination platform must perform an Address Resolution Protocol (ARP) sequence to get the MAC address of the source platform that made the ping request. This ARP sequence is called an ARP request message.

Since the ARP packet is a broadcast message, eth0 of the source platform responds with the MAC address, which is incorrect for eth1.

If the ARP broadcast returned the wrong MAC address for eth1, every ping reply from the destination platform has the incorrect destination MAC address. Therefore, eth0 is receiving all the responses instead of eth1. If Wireshark is used to view the packet traffic, it looks like every ping request has a matching ping reply except that none of the response packets are received by eth1, causing a ping failure.

For example, in Figure 10-2, the highlighted ping reply is to a destination MAC address of d4:f5:13:87:0b:8c, which is the MAC address associated with eth0.