网卡参数 LOWER_UP啥意思？

exright

ip add显示网卡地址：

eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast qlen 1000


请问 LOWER_UP啥意思？

exright

没Google到解释！
谁能解释下！

aplah

啥os啊?

mjslz

都不晓得咯，硬是喊

exright

版本如下：

1. [root@localhost ~]# uname -r
   
2. 2.6.18-128.el5
   
3. [root@localhost ~]# more /etc/redhat-release
   
4. Red Hat Enterprise Linux Server release 5.3 (Tikanga)
   
5. [root@localhost ~]# iptables -V
   
6. iptables v1.3.5

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我注意了下，2.4内核的Linux并没有LOWER_UP这个属性！

aplah

lz把命令的输出全部贴出来吧，别的linux版本没发现这种情况啊

exright

1. [root@localhost ~]# ip add
   
2. 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue
   
3.     link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
   
4.     inet 127.0.0.1/8 scope host lo
   
5.     inet6 ::1/128 scope host
   
6.        valid_lft forever preferred_lft forever
   
7. 2: eth0: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast qlen 1000
   
8.     link/ether xx:xx:xx:xx:xx:xx brd ff:ff:ff:ff:ff:ff
   
9.     inet 172.16.1.100/24 brd 172.16.1.255 scope global eth0
   
10. 3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast qlen 1000
    
11.     link/ether  xx:xx:xx:xx:xx:xx brd ff:ff:ff:ff:ff:ff
    
12.     inet 172.22.6.1/24 brd 172.22.6.255 scope global eth1
    
13.     inet6 xxxx::xxxx:xxxx:xxxx:xxxx/64 scope link 
    
14.        valid_lft forever preferred_lft forever
    
15. 4: sit0: <NOARP> mtu 1480 qdisc noop
    
16.     link/sit 0.0.0.0 brd 0.0.0.0

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aplah

搜索了下，一种解答是

Attatched is a patch for the LOWER_UP flag in 'ip link/addr' output.
Useful to check if network cable is inserted or not.

另一种附链接http://www.spinics.net/lists/netdev/msg134538.html

aplah

linux's mail list discuss http://lists.busybox.net/pipermail/busybox/2008-June/031741.html

advise ask this question in the linux kernel,pls

exright

Attatched is a patch for the LOWER_UP flag in 'ip link/addr' output.

Useful to check if network cable is inserted or not.

谢谢aplah的帮忙！不过英文看不太懂！
感觉LOWER_UP似乎是物理电路接通，是低压弱电（LOWER），非高压强电（POWER）；那么<BROADCAST,MULTICAST,UP>此UP相较于LOWER_UP似乎是OSI的第一层物理层的联通。
不知道猜测的对不对！