Tag: hardware

WoL – Wake On LAN

If a computer on local LAN network is turned off and administrator needs to do some regular maintenance on it, he will need to use Wake-On-LAN (WoL) to power the system up remotely.

Of course, network devices need to be configured to enable that kind of “magic” packet forwarding.

NIC cards on machines need to support WoL for this to work, but we don’t bother with this here..

WoL is sending “magic packets” to computer NIC card in order to start the system up. NIC which supports WoL is still receiving power when PC is turned off. NIC then keeps listening on the network for the magic packet and if received it will initialise the system boot process and power up the PC.

Magic packet is specially crafted network directed broadcast packet typically sent with connectionless UDP, port 7.

You would usually have a WoL server somewhere on you network which will be used to source magic packets. If you send magic packets across network segments (between VLANs or from some remote subnet), last router in the path, one having client subnet locally connected, needs to be configured with directed broadcast. The first router on the path, router with server subnet locally connected, should have ip helper configured pointing to directed broadcast IP address (in our case

In our example below, both ip helper and directed broadcast are configured on the same L3 device since this is the only router connecting two subnets.

Directed broadcast on Cisco devices is off by default since IOS 12.0 and needs to be configured on specific subnets where WoL will be needed.

You need directed broadcast because PC which needs to be woken up is asleep and while asleep it will not have an IP nor it will respond to ARP. Only way to get some packets to that PC without an ARP resolution is by using local subnet L2 broadcast.

Furthermore, we can surely assume that your PCs are connected to L2 Access Switch. That switch will not know to which port is the PC connected while that PC is asleep. Only a Layer 2 broadcast (and unknown unicast) will be sent out all ports on a switch.

Network – What is network exactly?

The term “network” is by and large referred to computer’s network that is encompassed different types of hardware and computers. The key reason of such set up is to have the transportation of data and communication lenience. Nowadays, versatile technologies are used in these systems which are generally included: wired equipment, wireless and exotic technologies.

What is network?But whenever you will think about the major threats that lurk towards these networking systems, the point of their security will first come to your mind. Commonly, two types of security are significant in order to prevent invasions from somewhere else to your system. And these security measures can be installed in the form of personal firewall and encryption systems. You can avoid potential security vulnerability to your network by putting in firewall while another renowned approach to secure your computers connection is by encrypting traffic at the top level in TCP/IP stack that is known as packet level encryption.

In short, networking endows with manifold benefits and these are file sharing, hardware sharing, computer’s mobility and internet connection sharing etc. Get advantage from these facilities if you are an owner of an institute or organization.