netstat命令可用於檢查網(wǎng)絡(luò)連接、路由表、接口統(tǒng)計信息等。 1. 使用netstat -tuln可查看處於監(jiān)聽狀態(tài)的TCP和UDP連接，幫助識別哪些服務(wù)正在接受連接；2. 使用netstat -r可查看內(nèi)核路由表，用於排查連接問題；3. 使用netstat -i可監(jiān)控網(wǎng)絡(luò)接口的統(tǒng)計信息，如丟包情況；4. 可結(jié)合grep、watch等工具增強(qiáng)功能，但現(xiàn)代系統(tǒng)推薦使用ss替代netstat。

The netstat command shows network connections, routing tables, interface statistics, masquerade connections, and multicast memberships. It's a handy tool for checking what's happening with your system's network activity.

Check Active Network Connections

One of the most common uses of netstat is to see what active connections are open on your machine. Running something like netstat -tuln will show you TCP and UDP connections in a listening state, along with their local addresses and ports.

• -t stands for TCP
• -u for UDP
• -l lists only listening ports
• -n prevents DNS lookups (shows IPs instead of hostnames)

This can help identify which services are currently accepting connections or actively communicating.

You might see entries like:

 tcp6 0 0 :::80 :::* LISTEN

That means the web server (port 80) is listening on all IPv6 interfaces.

View Routing Table Information

Running netstat -r gives you an overview of the kernel's routing table. This is useful when troubleshooting connectivity issues or understanding how traffic is routed through the network.

You'll typically see columns like Destination, Gateway, Genmask, Flags, MSS, Window, and irtt. The Gateway column tells you where packets are being sent next — basically, your system's idea of “how to get out.”

If you're used to using ip route , this is just another way of looking at similar data but presented differently.

Monitor Network Interface Statistics

Want to know how much data has been sent or received on each interface? Try netstat -i . It gives a quick summary of packet counts, errors, and interface status.

It helps spot things like high packet loss or interface errors that might point to hardware or configuration problems. For example, if one interface shows a lot of dropped packets, it could be misconfigured or experiencing congestion.

Also, if you're debugging performance issues, seeing unusually high numbers here can be a red flag.

Combine With Other Tools for Better Insights

While netstat is powerful on its own, pairing it with tools like grep , awk , or even watch can make it more useful.

For example:

• watch netstat -tulnp lets you monitor changes over time
• netstat -antp | grep :22 filters SSH connections
• netstat -s gives you detailed protocol statistics

Keep in mind that on modern Linux systems, ss (socket statistics) is often recommended as a faster alternative. But knowing netstat still comes in handy, especially on older systems or when reading legacy documentation.

基本上就這些。

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