What does TraceRoute mean?

TraceRoute means "route tracing" in Chinese. It is a computer command that can use the ICMP protocol to locate all routers between the user's computer and the target computer. The syntax is "tracert [-d] [ -h maximum_hops] ... target_name".

The operating environment of this tutorial: Windows 7 system, Dell G3 computer.

The traceroute (tracert on Windows) command uses the ICMP protocol to locate all routers between your computer and the target computer. The TTL value can reflect the number of routers or gateways that the data packet passes through. By manipulating the TTL value of the independent ICMP call message and observing the return information that the message is discarded, the traceroute command can traverse all routers on the data packet transmission path.

Principle

The program uses increasing time to live (TTL) value to achieve its function. Every time a packet passes through a router, its lifetime is reduced by one. When its lifetime is 0, the host cancels the packet and sends an ICMP TTL packet to the sender of the original packet.

The TTL value of the first 3 packets sent by the program is 1, the next 3 packets are 2, and so on, it gets a series of packet paths. Note that IP does not guarantee that every packet takes the same path.

Definition

It consists of tens of thousands of local area networks and millions of computers spread across the world, and is interconnected through the TCP/IP protocol for heterogeneous networks. communication. In the Internet, information is transmitted from one end to the other through transmission media and equipment (routers, switches, servers, gateways, etc.) in many segments of the network. Each device connected to the Internet, such as hosts, routers, access servers, etc., generally has an independent IP address. Through Traceroute we can know the path that information takes from your computer to the host at the other end of the Internet. Of course, the path a data packet takes from the same starting point (source) to the same destination (destination) may be different every time, but basically the route taken is the same most of the time. In UNIX systems, we call it Traceroute, and in MS Windows, it is Tracert. Traceroute measures how long it takes by sending small packets to the destination device until they return. Traceroute tests each device on a path three times. The output includes the time (ms) of each test and the name of the device (if available) and its IP address.

Parameter description

tracert [-d] [-h maximum_hops] [-j computer-list] [-w timeout] target_name

This diagnostic utility performs the following tasks by sending Internet Control Message Protocol (ICMP) response messages with different time-to-live (TTL) to the destination. Determine the route to the destination. Each router along the path decrements its TTL value by at least 1 before forwarding the ICMP echo message, so the TTL is a valid hop count. When the TTL value of the packet is reduced to 0, the router sends an ICMP timeout message back to the source system. Tracert determines the route by sending the first response message with a TTL of 1 and incrementing the TTL value by 1 each time on subsequent sends until the target responds or the maximum TTL value is reached. Routers can be identified by examining the ICMP Exceeded (ime Exceeded) information sent back by intermediate routers. Note that some routers "quietly" drop packets with expired time-to-live (TLS) and are ineffective for tracert.

Parameters

-d

Specifies that the address will not be resolved by computer name.

-h maximum_hops

Specifies the maximum number of jumps to find the target.

-j computer-list

Specify loose source routes in computer-list.

-w timeout

Wait for the number of milliseconds specified by timeout for each response.

target_name

The name of the target computer.

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