Archive for July, 2009

If you’ve ever wanted to check on the status of your Ethernet links, you’ve probably used the ip commands (or ifconfig) to view some basic information.  However, you might have noticed these commands do not tell you what the current link speed is, or other possibly important details.  That’s where ethtool comes in.

[jonmoore@megaton ~]$ sudo ethtool eth0
Settings for eth0:
Supported ports: [ MII ]
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: MII
PHYAD: 1
Transceiver: external
Auto-negotiation: on
Supports Wake-on: g
Wake-on: d
Link detected: yes

As you can see, ethtool will show you the support modes, as well as the current mode.  From the above example, I’m currently connected at 1000Mb/s at Full Duplex.  Very nice.

Check out the ethtool man page for more useful commands.

Many times I’ve started a traceroute to either a mistyped IP address, the wrong IP or something else that I would really rather not wait for 30 hops to time out before moving on. When doing the traceroute the device tells yous to “Type escape sequence to abort,” but doesn’t share what exactly this escape sequence is. After a bit of googling and finding a few references here and here I’ve found an answer.

This elusive key combination is CTRL+SHIFT+6 twice. I’ve had mixed results using it, but it appears, that holding CTRL+SHIFT while hitting 6 works sometimes, and others retyping the entire combination works. Either way, it’s been a help.