IFCONFIG Does Not give You Link Status; ETHTOOL Does
For some reason that is a complete mystery to me, RHEL does not give you the link status when you run
# ifconfig -a. This makes it incredibly hard to debug link integrity issues! Buried amongst all of Red Hat’s proprietary commands, however, is a utility called ethtool, which does give you the status of your link.
Since ethtool is used for querying settings of an ethernet device and changing them, it does a lot more than just give link status. Amongst other things, you can use it to turn on or off autonegotiation on your network card. Run # /sbin/ethtool -h for full usage.
Here’s how you use it to see if your server has link:
# /sbin/ethtool eth0
You should see something like this:
Settings for eth0:
Supported ports: [ TP ]
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
Supports auto-negotiation: Yes
Advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
Advertised auto-negotiation: Yes
Speed: 1000Mb/s
Duplex: Full
Port: Twisted Pair
PHYAD: 1
Transceiver: internal
Auto-negotiation: on
Supports Wake-on: g
Wake-on: d
Link detected: yes
Sun Happy Meal Card???
So we all know that Sun is a cool company with a great sense of humor, but they really outdid themselves when they named this combination SCSI / Ethernet card Happy Meal!
It’s a pretty old card, and honestly I had forgotten that I had installed it in my test system until I setup REL 3 on it last week. For some reason, the Red Hat installer wanted to remove the device before adding it back in. Luckily I had my camera with me when I saw the hardware detection message pop up.
