Tcp/ip:ip Route Selection

Principle: IP Search Routing table: 1. Search for matching hosts. 2. Search for a matching network address. 3. Search for default table entries.

Routing table: G: Direct Routing (g) and indirect routing (excluding G) are distinguished

H: The destination address is a full host address/network address. The host address must exactly match the destination address. Network addresses match only the network and subnet numbers that match the destination address.

D:ICMP returns the message.

The complexity of the host routing table depends on the network topology in which the host resides:

1. The simplest is that the host is not connected to any network and only communicates with itself. Only the loopback interface is included.

2. The host is connected to another regional network, only the host on the LAN, including the loopback interface and LAN.

3. The host accesses other networks (such as the Internet) through a single router, adding a default table to the router

4. Add additional hosts or network routes.

ICMP Redirect error: When an IP packet should be sent to a router, the router receiving the packet broadcasts an ICMP redirect error message to the sender.

Function: Perfect the router table, the host learns by accepting the redirect Message table, change the default route.

The recipient of the ICMP redirect message must see three IP addresses: 1. The IP address that caused the redirect (that is, the data for the ICMP Redirect message, located at the header of the IP datagram)

2. redirected routing table address

3. The IP address of the router that should be used.

Tcp/ip:ip Route Selection