About the detailed setting method of the router ip address

Is the setting of the ip address important? Many people will ask this question, in fact, it is really important, because it means that you have a smooth Internet access or can not access the Internet. . When new broadband is installed or a new Internet access device is added to the network, it often encounters "ip address conflict" or dns problem. These are not hardware failures of the router device or the computer network card itself, but the setting of the ip address. The problem of the division of the network segment. In a simple network, as long as the ip address is automatically obtained, there is no need to do redundant settings, but in the deconstructed slightly more complicated LAN, the router's ip address setting, network segmentation and gateway ip address allocation, Need to have some skills. Here is a comprehensive analysis of how to set the router IP address, gateway and DNS.

Why are these external router IP addresses looking for computers in the school? It is not difficult to find out from the collected data analysis that these external hosts are mainly looking for internal fixed three computers.

How can I correctly set the router IP address? Here we mainly introduce the specific steps of the router IP address. Originally, when the router receives a packet that does not know the router's IP address (that is, the router does not know the destination route), it will try to send an ARP broadcast to resolve. If the target host responds to the ARP broadcast, the router will put The packet is forwarded to the target host.

If the router does not receive a response, it will send an ARP request for the next 4 packets. If the 6th packet arrives, the MAC address of the target host is not resolved. By default, Next, the router will discard the sixth and subsequent packets in the next 20 seconds and return the ICMP information of the host unreachable to the source host.

The first sentence in the record of computer B can also be proved. The router sends an ARP query to the network segment to find the computer with the router IP address "222.222.222.191", and the result is no computer. Correspondingly, the router considers that there is no target host in the network segment, so returning an ICMP message to the source computer indicates that the target host is unreachable to notify the source host that there is a problem and discard the original data packet. At this point, the problem is clear. The original ICMP recorded by the router is the “Destination Unreachable” message sent by the router to the source address. So why are these external router IP addresses looking for computers in the school? It is not difficult to find out from the collected data analysis that these external hosts are mainly looking for internal fixed three computers. After checking the history log, you can find the main records of the three computers:

07:52:19 Jul 09 07:50:02 %ACL_LOG-I-PERMIT, ACL [out]

on "uplink" TCP 222.222.222.136:3159 -> 61.173.209.101:6881

08:00:15 Jul 09 07:53:50 %ACL_LOG-I-DENY, ACL [out ]

08:00:15 Jul ACL [out]

on "uplink" TCP 222.222.222.12:3194 -> 219.121.133.197:6883

08: 00:15 Jul 09 07:57:59 %ACL_LOG-I-DENY, ACL [out]

on "uplink" TCP 222.222.222.220:3196 -> 210.238.6.177:6881

The ports of the three hosts connected to the target host are fixed between 6881 and 6889, and these ports are the common ports for BT downloads that are now more popular. It's no wonder that such logs have not appeared before, until the recent BT epidemic. The main reason is that when these hosts use BT download, they leave a record on the BT server, so that other hosts can download resources to these hosts, and when these hosts are shut down, the router tells them that they cannot find these hosts.