Detailed description of ifconfig in linux

[Root @ XXX ~] # Ifconfig

Eth0 Link encap: Ethernet HWaddr 00: 0C: 29: C8: 87: DB

Inet addr: 192.168.5.103 Bcast: 192.168.5.255 Mask: 255.255.255.0

Inet6 addr: fe80: 20c: 29ff: fec8: 87db/64 Scope: Link

Up broadcast running multicast mtu: 1500 Metric: 1

RX packets: 215632 errors: 0 dropped: 0 overruns: 0 frame: 0

TX packets: 87 errors: 0 dropped: 0 overruns: 0 carrier: 0

Collisions: 0 FIG: 1000

RX bytes: 15503343 (14.7 MiB) TX bytes: 10634 (10.3 KiB)

Interrupt: 177 Base address: 0x1400

HWaddr: the MAC address of the NIC, which is fixed in the NIC at the factory.

Inet addr: IP Address

Bcast: broadcast address. Specifies the IP address used to send broadcast messages. Use the local IP address and subnet mask to create the default broadcast address. For example, the destination address 192.168.5.255 is broadcast to all hosts on the 192.168.5.0 network.

Mask: Subnet Mask. The subnet mask indicates the IP address that identifies the network and the host. The internet is separated by various routers and gateway devices into many CIDR blocks. To identify different CIDR blocks, you need to divide the 32-bit IP addresses into two parts: the network number and the host number, each host with the same network number is located in the same network segment and can communicate with each other directly. The communication between hosts with different network numbers needs to be forwarded through the router. The division of network and host numbers requires an additional subnet mask), which cannot be determined by the value of the IP address itself. That is to say, the network number and host number are not related to whether the IP address is A, B, or C. In this way, multiple subnets can summarize mmarize) into an Internet network. For example, eight sites have applied for a class C network, and the network number is originally 24 bits, however, when these eight sites are connected to the Internet through the same ISPInternet service provider, their network numbers have the same 21-bit height, and only the lower three are different, these eight sites can be summarized. On the Internet, only one route table item is required. data packets arrive at the ISP through the Internet router, and then route to a site through the secondary router on the ISP side. The IP address and subnet mask can be used to obtain the network number. The host number ranges from 0 to 1, which is the subnet address range. There is also a more concise representation of the IP address and subnet mask. For example, 140.252.20.68/24 indicates that the IP address is 140.252.20.68, and the 24-bit high subnet mask is 1, that is, 255.255.255.0.

Instance 1

IP address 140.252.000068 8C FC 14 44

Subnet Mask 255.255.255.0 FF 00

Network No. 140.252.20.0 8C FC 14 00

Subnet address range: 140.252.20.0 ~ 140.252.20.255

Instance 2

IP address 140.252.000068 8C FC 14 44

Subnet Mask 255.255.255.255.240 FF F0

Network No. 140.252.20.64 8C FC 14 40

Subnet address range: 140.252.20.64 ~ 140.252.20.79

Inet6 addr: IPv6 address

"UP" indicates that the network card is enabled. "RUNNING" indicates that the network card of the network card is connected. "MULTICAST" supports MULTICAST)

MTU: The maximum transmission unit.

The Data Length in an Ethernet frame is defined as a minimum of 46 bytes, a maximum of 1500 bytes, and a minimum of 46 bytes for ARP and RARP packets. Fill in the following bits. The maximum value of 1500 is the maximum transmission unit MTU of Ethernet. Different network types have different MTU. If a data packet is routed from Ethernet to the dial-up link, the data packet length is greater than the MTU of the dial-up link, fragmentation is required for data packets ). Note that the MTU concept refers to the maximum length of the payload in a data frame, excluding the length of the frame header.

RX and TX:

RX indicates receiving data packets

TX indicates data packet sending.

If your network card has been configured but still cannot communicate with other devices, you can analyze the fault cause from the display data of RX and TX. In this case, if you see an increase in the number of packets received and transferred (packets), the IP address of the system may be in disorder; if you see a large number of errors (errors) and Collisions), it is likely that there is a problem with the network transmission media, such as network cable failure or hub damage.

Collisions: Description of network signal collision

Txqueuelen: the length of the transport delay zone.