10 tips, each summarized in a sentence or two. Speed up your WAN, Build a lab, know your apps, virtualization pitfalls, speed up backups, and more.

If you’re running an older distribution of Linux or you just find that the kernel module is unavailable because your RealTek RTL series PCI-Express Ethernet card is just too new, then you’ll need to install the driver manually.

Synergy lets you easily share a single mouse and keyboard between multiple computers with different operating systems, each with its own display, (and here’s the key part) without special hardware. It’s intended for users with multiple computers and monitors on their desk. Run synergys (the server daemon) pointing to your configuration file on one computer. You can run it as your regular desktop user too Then run the synergyc (client daemon) on the other computer and give it the ip address of the server computer.

The Category 5e standard guarantees performance of attenuation, return loss, propagation delay, delay skew, NEXT, Power-sum NEXT, ACR, power-sum ACR, ELFEXT, and power-sum ELFEXT to a nominal range of values at 100 MHz. The Category 6 standard guarantees to 250mhz. Cat6 is more expensive and doesn’t get you any improvement right now unless you’re running 10Gbase-T hardware. Cat5e are easy to make. Just get a spool, a crimper tool, and some rj45 jacks. If money isn’t a factor, run cat6 or fiber, and run multiple cables at a time. Get fancy punch down terminals and build a wiring closet with fancy lighting. And pay a high end home theater company to do it all for you.

These two scripts are called when you start a qemu or kvm virtual machine. I removed the openvpn –mktun and –rmtun commands because qemu handles it for you.

TUN is for IP tunneling. TAP is for Ethernet tunneling. Check out vtun if you’re looking to get networking working in qemu or kvm for virtual tunnels over tcp/ip networks with traffic shaping, compression, and encryption. vtun also supports serial and pipe tunnels.

Capture filters are completely different than display filters, and for some reason it’s not immediately evident when you’re in Wireshark to understand what the syntax is for capture filters. Capture filters don’t follow these rules at all. But if you’re familiar with tcpdump, then you already know how to limit the capture with filters.

CK’s that contain no data are not reliably transmitted by TCP. If zero window probing is not supported, a connection may hang forever when an ACK segment that re-opens the window is lost. This type of attack has been realized since 2006. This means that an application or firewall must selectively abort TCP connections that appear malicious by staying in the persist state and consume large amounts of resources.

Assuming you’ve already installed and configured your directory to use TLS encryption, you should verify LDAP is working as you expect before you start streaming passwords and other important data across the wire. You can use Wireshark and it’s full blown gui interface, but it’s faster just to fire up tethereal for this test.

So you want to setup networking so virtual machines will have access to the outside world through your hosts network connection. To do this you’ll need to share your host’s external interface with virtual machines through a bridge. A bridge can join two network segments and be used to inspect all Ethernet frames that pass between them. Create a bridge and a tunnel interface. Assign the tunnel and your host’s Ethernet interface to the bridge. Connect the bridge to the outside world. Your host uses the network card in promiscuous mode to handle packets for other interfaces connected to the bridge.