Configure a Radius server on Windows Server to authenticate Cisco VPN users

A Virtual Private Network (VPN) allows to connect to a private network through the Internet, from anywhere in the world.

It may be very helpful to business users willing to access from outside the internal resources of their company.

In this post we’ll see how you can allow Active Directory users to perform the login to a VPN, configured on a Cisco router.

The setup includes a Cisco 1801 router, configured with a Road Warrior VPN, and a server with Windows Server 2012 R2 where we installed and activated the domain controller and Radius server role.
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How to balance the network traffic with Hot Standby Router Protocol (HSRP)

We’ve already wrote about the Hot Standby Router Protocol (HSRP) in our previous article. HSRP is a proprietary protocol developed by Cisco, that allows to decouple the IP addresses from the physical interfaces and to associate them to groups of interfaces, providing hardware redundancy.

In this article we’ll see how to balance the network load with the 2 HSRP groups, allowing to assign 2 virtual gateways to every group of PCs. The result will be a network scheme with load balancing that allows the 2 hosts to connect to the Internet even in case of failure of a gateway.
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How to configure Hot Standby Router Protocol (HSRP) with Cisco routers

When high-availability isn’t a priority but a requirement, router redundancy is mandatory. As every router has its own layer 3 address, it would be useful to have the possibility to use a single layer-3 address able to “move” from a router to another. Hot Standby Router Protocol (HSRP), a proprietary protocol developed by Cisco, allows to decouple the IP addresses from the physical interfaces and to associate them to groups of interfaces, providing hardware redundancy.

Technically speaking, HSRP sends its hello message to the multicast address 224.0.0.2 (all the routers inside the network) using the 1985 UDP port, to contact the other HSRP-enabled routers and estabilish the priorities between them: the primary router – with the higher priority – will work as virtual router (with its own IP and MAC addresses) and it will be used by the hosts as gateway; in case of failure of the primary router, the router with the second highest priority will become the default gateway.
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How to configure DHCP failover on Windows Server 2012 R2

Configuring the DHCP failover in your LAN is a simple operation to improve the reliability of the network.

There are two main ways to provide DHCP failover:

  • Load balancing
  • Hot standby

Load balancing allows to share the load between two or more DHCP servers while the Hot standby mode simply provide DHCP redundancy.

In this guide we adopted the Hot standby mode. The DHCP servers are two Windows 2012 R2 machine in the same domain (mandatory requirement).
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How to configure NIC Teaming on Windows Server 2012

Load balancing and failover (LBFO), also known as NIC Teaming, is a powerful feature introduced by Microsoft only with Windows Server 2012. With previous versions of Windows you could only rely on third party software, a curious limitation.

NIC Teaming allows an administrator to place in a team multiple network adapters being part of the same machine.

Working as a team, the network adapters improve bandwidth and protect from failures, sharing the same IP and network configuration.

The reason is pretty straightforward, if one of the adapters breaks, the others will take care of the local connectivity. Windows supports up to 32 adapters placed in a single team.
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How to reset NTFS permissions with ICACLS

File and folder permissions are really important to Windows. Sometimes a user may mess with the permissions causing software or even the operating system to work in an undesired way.

There’s a simple way to solve this kind of problems without headaches, using the ICACLS command.

Launch the command prompt as an Administrator and navigate through the tree of folders you need to fix.

Then launch the command ICACLS * /T /Q /C /RESET.

ICACLS will reset the permissions of all the folders, files and subfolders. After a while, depending on the number of file, the permissions will be fixed.

Sometimes, you may need to take the ownership of a tree of folders. You can use the command takeown /R /F * before launching the ICACLS.

Be careful, taking the owenership of system folders may break your operating systems.

Configuring and using Windows Deployment Services (WDS)

Windows Deployment Services (WDS) is a really interesting tool from Microsoft. It allows an administrator to remotely deploy Windows operating systems to machines booting from a network adapter.

In environments with a high number of clients WDS can be very useful, a new computer can be formatted just plugging the Ethernet, without any physical support like Windows DVDs or USB drives.

The configuration isn’t difficult but there are some requirements:

  • There must be an Active Directory Domain Services
  • At least one partition on the server must be formatted as NTFS
  • A DHCP server must be active to assign IP addresses to the WDS clients

Let’s see how you can configure and use the Windows Deployment Services.
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