What is icmp redirection?

What is icmp redirection ICMP redirection is one of the ICMP control packets. Under certain circumstances, when a router detects that a machine uses a non-optimized route, it will send an ICMP redirection packet to the host and request the host to change the route. The router also forwards the initial datagram to its destination. ICMP Application Analysis-although ICMP redirection is not a routing protocol, it can also guide the flow of data packets (to make the data flow to the correct gateway ). ICMP achieves this goal through ICMP redirection data packets (type 5, code 0: Network redirection. Figure 6 ICMP redirection 6 shows that the host PC needs to ping the loopback 0 address of router R2: 192.168.3.1, and the host determines that the target belongs to different network segments, therefore, it needs to send the ICMP request packet to its default gateway 192.168.1.253 (E0 interface of router R1 ). However, the host PC must first send an ARP request to request the MAC address of E0 (192.168.1.253) of router R1. When the router R1 receives the ARP request packet, it first uses the ARP response packet to answer the ARP request from the host PC (notifying the host PC: the MAC address of the E0 interface of the router R1 ). Then, it (router R1) forwards the ICMP request to the E0 interface of router R2: 192.168.1.254 (requiring router R1 to correctly configure the route to the network 192.168.3.0/24 ). In addition, router R1 also sends an ICMP redirection message to the host PC, notifying the host PC that the gateway for the host PC request address is 192.168.1.254. Vror2 R2 sends an ARP request message to the MAC address of the host PC, and the host PC sends an ARP response message to vror2 R2. Finally, vror2 R2 sends an ICMP Response Message to the host PC by obtaining the MAC address of the host PC. The content of the ICMP redirection package is shown in Figure 7 and figure 8. Note the values and meanings of the Type and Code fields in Figure 7 ICMP Baotou. Figure 7 ICMP redirection packet figure 8 ICMP redirection packet-if there are subsequent ICMP request packets, all event sequences except ARP messages are the same as described above. 9. Figure 9 ICMP redirection Event Sequence