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Posts in Networking
Getting DNS ping (aka nsping) to compile on Linux hosts
While debugging a DNS issue this week, I wanted to run my trusty old friend nsping on my Linux desktop. I grabbed the source from the FreeBSD source site, checked to make sure the bits were legit, then proceeded to compile it: Erf! The source archive I downloaded didn't compile, and from the error message it appears the function definition for dprintf conflicts with a function definition in libc. Instead of mucking around with map files, I changed all occurrences of dprintf to ddprintf…
$ read more →Getting notified when new hosts appear on your network
I had to debug an interesting network problem a few weeks back, and wanted to see when new hosts appeared on my network. While debugging the issue, I needed to find a way to get notified when a new host appeared (I didn't want to sit at a terminal reviewing the output from snoop and tcpdump). Enter arpwatch, which can be used to send alerts the first time a client issues an ARP request. This is actually quite handy, and the alerts you get my e-mail are rather useful: There are a slew of options to control who gets the e-mail, whether to use a saved packet capture instead of an active network connection, etc…
$ read more →Creating Linux bridging / tap devices with tunctl and openvpn
The more and more I play around with KVM virtualization, the more I realize just how useful Linux bridging is. In the Linux bridging world, a bridge device simulates a multiport Ethernet switch. To connect to the switch, you create a tap device that simulates a port on that switch. Once you have bridging configured on your host, there are two prevalent ways of going about creating taps…
$ read more →Configuring an OpenSolaris host to use a static IP address
I installed OpenSolaris 2009.06 yesterday, and noticed that the installer doesn't give you the option to configure a static IP address. Network address are retrieved via DHCP, which isn't an option for this host. To configure the host to use a static IP address, I changed the /etc/nwam/llp file. Here is the file before: And here is the file after: Now my host can take advantage of NWAM, and use the static IP I allocated for it!
$ read more →Viewing the status of NetworkManager managed links
As I mentioned in a previous post, I spent some time trying to get the NetworkManager to respect my custom DNS settings. When I was looking into this issue, I learned about the nm-tool utility. This nifty tool will print the status of each NetworkManager managed interface, as well as the connection state: I found the IPv4 settings section to be rather useful while I was debugging a network connectivity problem (nm-tool and ethtool make it SUPER easy to debug link problems), and will definitely be using this tool in the future!
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