Administrator Guide

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 56. 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.
UDP Helper
User datagram protocol (UDP) helper allows you to direct the forwarding IP/UDP broadcast traffic by creating special broadcast
addresses and rewriting the destination IP address of packets to match those addresses.
Configure UDP Helper
To configure Dell EMC Networking OS to direct UDP broadcast, enable UDP helper and specify the UDP ports for which traffic is
forwarded. See Enabling UDP Helper
Important Points to Remember
• The existing ip directed broadcast command is rendered meaningless if you enable UDP helper on the same interface.
• The broadcast traffic rate should not exceed 200 packets per second when you enable UDP helper.
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IPv4 Routing