Install Guide

ICMP Redirects
When a host sends a packet to a destination, it sends the packet to the configured default gateway. If the gateway router finds
that a better route is available through a different router in the same network, that is, the same data link, the gateway router
sends the source host an ICMP redirect message with the better route. The gateway router routes the packet to its destination
and the host sends subsequent packets to that particular destination through the correct router.
Dell EMC Networking OS supports both ICMP and ICMP6 redirect messages. The following diagram depicts a topology in which
ICMP redirect messages are useful.
Figure 51. ICMP Redirect
Host H is connected to the same Ethernet segment as SW1 and SW2. SW1 and SW2 are multi-layer switches which can route
packets. The default gateway of Host H is configured as SW1. Although the best route to the remote branch office host may
be through SW2, Host H sends a packet destined for Host R to its default gateway — SW1. After SW1 finds that the route to
Host R is through SW2, and that SW1 must forward the packet out the same Ethernet interface on which packet was received,
it forwards the packet to SW2 and sends an ICMP redirect message to Host H. Host H learns of the new route using the ICMP
redirect message and sends all future packets to the remote branch office host to SW2.
To enable ICMP or ICMP6 redirect messages, use the icmp6-redirect enable command.
NOTE: The icmp6-redirect enable command is applicable for both ICMP and ICMP6 redirects.
By default, Dell EMC Networking OS supports redirects on VLAN interfaces. For physical ports and port channel interfaces,
carve the fedgovacl CAM region.
410
IPv4 Routing