DHCP

DHCP is a major new feature for WinGate 2.1. Many new and existing WinGate users will not have heard of DHCP so this section is an introduction to the topic. DHCP allocates IP numbers to your client machines. You have probably had a little experience with dynamic IP allocation already. When a modem makes a PPP connection to an ISP, an IP number is often dynamically allocated to the modem.

Note: DHCP is a feature that is only available with a licensed version of WinGate. Therefore, the free one user license does not provide DHCP capabilities.

What is DHCP?

DHCP stands for ‘Dynamic Host Configuration Protocol’.

What does it do?

DHCP is a means for networked computers to get their TCP/IP networking settings from a central server. Importantly, DHCP assigns IP addresses and other TCP/IP configuration parameters automatically. WinGate DHCP is different from other DHCP servers, in that it can even figure out what IP addresses to allocate without the Administrator having to predefine pools of addresses (Scopes). It can also figure out what to set the clients' gateway and several other parameters too, so now, not even the Administrator needs to be a TCP/IP expert to operate the WinGate DHCP server. Full manual override of all automatic settings is also available, so an Administrator with specific requirements can still cater for these.

Why is this better?

DHCP eases both TCP/IP and WinGate configuration. Without DHCP, all the machines on a network had to have unique private static IP addresses assigned to them. DNS also required configuration. Many options on the TCP/IP setup can be problematic, and one wrong setting can prevent a client from getting the desired access. Existing WinGate users may remember that client machine TCP/IP configuration had 6 stages, for each machine. With DHCP you simply install TCP/IP and that is all that is required, no IP number, no messing with DNS settings! The DHCP client is installed as part of TCP/IP. If you already have TCP/IP installed, you simply select "Obtain an IP address using DHCP" (Windows NT), or "obtain an IP address automatically" (Windows 95).

If you want the easiest network setup, use DHCP. Qbik recommend DHCP as insurance against IP conflict and configuration errors.

How does it work?

When Windows starts on a client machine, the DHCP client that is built into Windows TCP/IP sends a broadcast packet on the network requesting an IP address. Any DHCP server that hears this request sends a response, an ‘offer’ of an IP address. This IP address is chosen from a range of acceptable IP addresses configured in the DHCP server. Each range of IP addresses is referred to as a scope. The client can then ‘accept’ the IP address. Any further configuration information is also forwarded to the client at that stage, including DNS server details. When a client has had an IP lease for half the lease time, it will request a new lease. It may receive the same or a different IP number. WinGate records information about each active Lease, and also integrates these with the WinGate rules, so you now have more information about the machines using WinGate.

How about my static IP addresses?

You do not need to worry about computers on your network that cannot use DHCP. They can still use their existing IP address. WinGate checks to see if it can ping an IP address before it will allocate it. If it can ping an address, it knows the address is in use, and so it will not allocate it to any other machine. If you prefer, you can also set excluded IP addresses in each scope that you create, or that WinGate creates for you.

What are Reservations?

Reservations are used if you want to guarantee that a specific computer will always be allocated a certain IP address, and that this address will not be allocated to any other computer. This is sometimes used where you have purpose-built applications that connect to specific hosts, which may themselves use DHCP to configure their networking. However, with WinGate's integration of DHCP with WinGate DNS, this will become largely redundant, as you are able to look up the IP addresses of machines by their computer name (NetBIOS name as opposed to their host name)

Reservations are also used if you wish to specify specific TCP/IP settings on a machine-by-machine basis.