linux ip a 命令查看网卡信息 UP 和 LOWER_UP 区别

[Thursdayday]

[root@desktop-24-53 ~]# ip a
2: enp3s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 6c:4b:90:ba:9a:f8 brd ff:ff:ff:ff:ff:ff
inet 10.101.24.53/22 brd 10.101.27.255 scope global noprefixroute dynamic enp3s0
valid_lft 2123733sec preferred_lft 2123733sec
inet6 fe80::8609:7356:48c7:5b71/64 scope link noprefixroute
valid_lft forever preferred_lft forever



这个UP 和 LOWER_UP 有哈区别 麻烦大神指点下

[X-i-n]

UP是三层的状态，接口已经逻辑上起来了。LOWER_UP是指链路物理状态，也起来了。 比如，插上网线，但是把接口ifdown以后，它就是DOWN（逻辑），LOWER_UP（物理）。

[X-i-n]

刚才实际测了一下，我对UP的解释有问题。这个是各种标志对应的描述。

引用

IFF_ALLMULTI Receive all multicast packets. IFF_AUTOMEDIA Auto media selection active. IFF_BROADCAST Valid broadcast address set. IFF_DEBUG Internal debugging flag. IFF_DORMANT Driver signals dormant (since Linux 2.6.17) IFF_DYNAMIC The addresses are lost when the interface goes down. IFF_ECHO Echo sent packets (since Linux 2.6.25) IFF_LOOPBACK Interface is a loopback interface. IFF_LOWER_UP Driver signals L1 up (since Linux 2.6.17) IFF_MASTER Master of a load balancing bundle. IFF_MULTICAST Supports multicast IFF_NOARP No arp protocol, L2 destination address not set. IFF_NOTRAILERS Avoid use of trailers. IFF_POINTOPOINT Interface is a point-to-point link. IFF_PORTSEL Is able to select media type via ifmap. IFF_PROMISC Interface is in promiscuous mode. IFF_RUNNING Resources allocated. IFF_SLAVE Slave of a load balancing bundle. IFF_UP Interface is running.

[X-i-n]

The LOWER_UP is the state of the Ethernet link (or other link layer protocol). It's defined as Driver signals L1 up, which basically means the cable is fitted and it can see another device on the other end of the cable. The UP means that it has been enabled. This can be controlled by you (or a script) using the ip link set <device> up of ifconfig <device> up command.

[Thursdayday]

引用 3 楼 X-i-n 的回复:

The LOWER_UP is the state of the Ethernet link (or other link layer protocol). It's defined as Driver signals L1 up, which basically means the cable is fitted and it can see another device on the other end of the cable. The UP means that it has been enabled. This can be controlled by you (or a script) using the ip link set <device> up of ifconfig <device> up command.

解释的非常到位，收益匪浅， 这些信息怎么查到的 。可否分享下 解题思路。

[X-i-n]

ip addr lower_up