Troubleshoot routers by using simple methods

Device failure, here to take out and share with you, I hope to be useful. Packet Internet groper (ping) This command is used primarily to check that the route is reachable because the Baochang of the command is very small.

So the speed of the online delivery is very fast, you can quickly detect whether the site is up to, generally you go to a site is you can run the command to see if the site is up to. If the ping is unsuccessful, you can predict that a router failure occurs in the following areas: whether the network cable is connected, the adapter is configured correctly, and the IP address is available. If the ping succeeds and the network is still unavailable, the problem is likely to be that in the software configuration of the network system, ping success can only guarantee a connected physical path between the current host and the destination host. Its use format is at the command prompt type: Ping IP address or host name, execution results show response time, repeat this command, you can find the Ping report response time is different.

Note that 5 packets have been sent, but we encountered a timeout on the first packet, and all other packets were answered on average in 49 milliseconds. In fact, this does not necessarily mean that it has a problem, in fact, this situation is very much seen, the first data Bau, this is very easy to explain. The Ethernet protocol runs on the 2nd layer of the OSI model, while IP and ICMP run on the upper layer 3rd. Before we can communicate with a shipping router, we must convert the 3rd-tier address to the 3rd-tier address, which takes time, and the ping default timeout is only two seconds. We can't convert an IP address to a MAC address fast enough to prevent the first data Bau, and the subsequent packet does not need to convert the MAC address because it has been saved in the ARP table. If we try to send the same ping immediately after the first ping, we should not see the first data Bau, because the ARP cache still stores the MAC address of the remote router failure.

Note that all packets are received this time, and in some cases, several packets may not be received. One of the things we can think of immediately is that there is a problem with the ISDN (DNN) connection. If the data link happens to have a router failure while the ping is being sent, all 5 packets may time out before the connection is restored. In this case, you can change the definition of the information you are interested in, or you can use another method before you try to send the ping command, which is the extended ping.

Extended Ping

There is another problem with the ping command to note that, by default, the user-mode ping command sets the TTL component to 32. Ping encounters each routerIn the case of failure, this value will be decremented by 1. If the value of the TTL becomes 0, the last router failure sends back an ICMP timeout message. If you have a very long path, then this value may not be enough. In a large network, you must use an extended ping to check the connectivity of your network. There are some differences between the

Extended ping command and the user-style ping command, for example: extended ping We must activate to use. It supports only IP protocols, AppleTalk, and IPX protocols, and does not support protocols such as Apollo, CLNX, DECnet, Vines, XNS, and one of the most important advantages is that we can change the default values used by the ping command, and after changing these values, You can use the same application for many different tests. The size of the

Packet can also be changed, and its default value is 100 bytes. When the network load is large, it can be used to check the status of the connection. When the packet size is the default value of 100 bytes, the ping command often fails to expose any exceptions to the network, but when you increase the packet size to 500 bytes, you can see significant connection loss or significant changes in response time. When you perform baseline profiling of your network, you should record the throughput speed of the large, medium, and small ping commands in the document. This will help you to accurately describe the operation of the network under different load levels.

When you set this parameter, be careful not to set it to the extent that it will interfere with other factors. If you set the packet size to 10,000 bytes, you can be sure it will produce results that you don't expect. One of the reasons for this is that the Ethernet machine must split the packet into the size that the Ethernet can handle before it can be sent on the network line. After a packet is received remotely, the packet is grouped again. This combination takes longer than you want, and causes it to explain the speed of the connection, based on factors other than the time required for the ping. When you change the size of the packet, use a reasonable method. Observe the output of the command below, and notice how the ping is
  that causes a timeout because the packet size increases to a maximum of 18,024 bytes;