What is ICMP redirect? and what is Proxy ARP?

-Hi Not sure about how boths works..... can anyone please explainme how do they work? what is the difference? thanskThe ICMP Redirect message is only sent in the following situation:



1. Host A is sending a packet to Host B. Host A's default IP router is router R1. Because Host B is a remote host, Host A forwards the packet destined for Host B to its default router R1.



2. R1 checks its routing table and finds that the next hop for the route to the network for Host B is router R2.



3. If Host A and R2 are on the same network that is also directly attached to R1, an ICMP Redirect message is sent to Host A informing it that R2 is the better route when sending to Host B.



4. Router R1 then forwards the IP datagram to R2.



5. Host A adds a host route to its routing table for Host B's IP address with router R2's IP address as the forwarding address. Subsequent datagrams from Host A to Host B are forwarded by means of router R2.



To better understand how proxy ARP works, below is an example of an interaction between two hosts: Host A in Subnet A and Host C in Subnet B.



1. Host A needs to send packets to Host B. Host A believes that it is directly connected to Host B鈥檚 subnet so Host A sends an ARP request to Host B.



2. In order for Host A to connect to Host B, Host A should first determine Host C鈥檚 MAC address. To do this, Host A broadcasts a new ARP request on Subnet A.



3. The ARP request is included in an Ethernet frame with Host A鈥檚 MAC address. The ARP request reaches all nodes in Subnet A, including the interface of the router. The request, however, does not actually reach Host B.



4. The router then replies to Host A with the router鈥檚 own MAC address. This is called the proxy ARP reply given by the router to Host A.



5. Host A then updates its ARP table. It sends the packets to the router, then the router forwards the packets to Host B.





No more confusions :)