Functions and usage of three network management tools in Linux

Article title: Functions and usage of three network management tools in Linux. Linux is a technology channel of the IT lab in China. Includes basic categories such as desktop applications, Linux system management, kernel research, embedded systems, and open source.

This article describes network performance management techniques for Linux systems. it mainly describes how to use route, netstat, and tcpdump network management test tools and their functions.
Route

When configuring the network, you must specify the path through which the packet is received for the machine. In Linux, a command route is provided, which can be used to set a static route for the Nic configured by the ifconfig command. This setting is usually introduced in/etc/rc. d/rc. inet1 during system boot.

Here are several examples to illustrate how to use the route command:

Route add-net 127.0.0.0

This command adds a route entry with a specified address or network to the routing table. Note that the network is A Class A address, the mask is set to 255.0.0.0, and the newly added entry is connected to the lo device.

Route add-net xxx. xxx netmask limit 255.255.0 dev eth0

This command adds a route for the host whose IP address is xxx. xxx, and its network mask is set to 255.255.255.0.

Route del-net xxx. xxx

This command will delete the route of the network xxx. xxx.

The route command can also be used to conveniently manage the route information of the entire network. the output result is the route table of the network. As follows:

[Root @ lee/root] # route

Kernel IP routing table

Destination Gateway Genmask Flags Metric Ref Use Iface

10.10.8.20.* 255.255.255.255 UH 0 0 0 eth0

10.10.8.0*255.255.255.0 U 0 0 0 eth0

127.0.0.0*255.0.0.0 U 0 0 0 lo

Default dgc8.njupt.edu 0.0.0.0 UG 0 0 0 eth0

Default dgc8.njupt.edu 0.0.0.0 UG 1 0 eth0

[Root @ lee/root] #

The meaning of each field in the output result is:

· Destination indicates the Destination IP address of the route.

· Gateway indicates the host name or IP address used by the Gateway. The output "*" indicates no Gateway.

· Genmask indicates the network mask of the route. Which of the following is the author of the survey about this problem? Why? ? U? Enmask and the IP address of the data packet are operated by bit "and" to set the route.

· Flags indicates a route entry. The available flag indicates that the route is starting. H indicates that the target is a host, G indicates that the gateway is used, R indicates that the dynamic route is reset. D indicates that the route is dynamically installed, M indicates modifying the route ,! Indicates that the route is denied.

· Metric indicates the sales volume of the route.

· Ref indicates the number of other routes that depend on the current status of the current route.

· Use indicates the number of route table entries used.

· Iface indicates the destination network of the packet sent by the route.

By viewing the output information, we can conveniently manage the route table of the network.