Think Like A Computer

24 08, 2011

The Routing Table

By D.A.R.Y.L.|2020-02-02T18:16:23+10:00August 24th, 2011|Categories: TCP/IP|Tags: Networking, routers, Routing, routing table, TCP/IP|6 Comments

Welcome to part 2 in a 3 part series of articles about routers and routing . If you have arrived here directly through a search engine you may wish to read Part 1 – How Does a Router Work? first. Here we are going to look at the routing table. All network devices that use the TCP/IP protocol have a routing table, even your Windows PC has one. ALL devices use their routing table to determine where to send packets. Without a routing table your PC wouldn’t even be able to communicate with computers on the same subnet. Here is a screenshot of the routing table of my PC. To see your own routing table open a command prompt by typing CMD in the run or search box. Then at the command prompt type “”route print” and press enter.

19 08, 2011

Network Address Translation

By D.A.R.Y.L.|2020-02-02T18:16:23+10:00August 19th, 2011|Categories: TCP/IP|Tags: NAT, TCP/IP|10 Comments

This article assumes you have an understanding of computer networking basics. Network Address Translation has several advantages but its primary goal is to allow a single Internet IP address to be shared on a network by multiple devices. Your home router has built in NAT capabilities and does all this automatically. It works by your ISP assigning you ONE IP address to your router, NAT then allows multiple computers to access the Internet through this shared IP address.

9 08, 2011

Why Multiple VPN Connections To The Same IP Fail

By D.A.R.Y.L.|2020-02-02T18:16:23+10:00August 9th, 2011|Categories: TCP/IP|Tags: NAT, Networking, pptp, pptp passthrough, TCP/IP, vpn|7 Comments

In a previous article I explained what PPTP passthrough is and how it works. In this article I will explain why multiple VPN connections fail with certain routers. This issue only affects PPTP connections and it is directly related to PPTP passthrough. Here is a brief comparison of how NAT handles PPTP VPN connections differently to normal connections. Read the PPTP passthrough link above for more details: When computers make normal outbound connections the source IP address is NATed to the public IP. Source ports are used to uniquely identify the multiple connections. When PPTP clients make outbound connections the same thing happens but the call ID AND destination IP is used instead of source ports to uniquely identify the VPN connections.

28 07, 2011

PPTP Passthrough and How It Works

By D.A.R.Y.L.|2020-02-02T18:16:24+10:00July 28th, 2011|Categories: TCP/IP|Tags: NAT, Networking, pptp, pptp passthrough, TCP/IP, vpn|11 Comments

Most computers connect to the Internet through a NAT device (usually a router). PPTP natively doesn’t work with NAT. Since most VPN connections start from behind a router this is a very common problem. PPTP passthrough addresses this by allowing VPN connections to traverse a NAT with ease. NAT (or more specifically PAT) can’t function without the use of ports. It is important you understand how NAT functions and it’s reliance on ports. If unsure I would advise reading up on network address translation first. NOTE: With some routers multiple VPN connections is not supported.

24 07, 2011

Moving Files on the Same NTFS Volume DOES Inherit Permissions

By D.A.R.Y.L.|2020-02-02T18:16:24+10:00July 24th, 2011|Categories: Hardware, Windows 2008, Windows 7|Tags: ACL, NTFS, NTFS Permissions, permissions, Windows|11 Comments

Most of you reading this will no doubt already have some idea of how file permissions are handled when moving or copying files to and from NTFS drives. The following behaviour is expected: When copying a file from one NTFS volume to a folder on another volume the file inherits the permissions of the destination folder. When copying a file from one folder to new a folder on the same NTFS volume the file inherits the permissions of the destination folder. When moving a file from one NTFS volume to a folder on another volume the file inherits the permissions of the destination folder. When moving a file from one folder to new a folder on the same NTFS volume the file retains the permissions.

18 07, 2011

How A Router Works (and IP routing)

By D.A.R.Y.L.|2020-02-07T16:34:12+10:00July 18th, 2011|Categories: TCP/IP|Tags: Networking, routers, Routing, TCP/IP|8 Comments

Welcome to part 1 in a 3 part series of articles about routers and routing. In part 1 we will cover how routers works, part 2 talks about the routing table and part 3 covers IP routing. So, how does a router work? Well, before we get into that you should know the basics of what the IP address is, subnet mask and default gateway before continuing. If you don’t have a read of networking basics first.

16 06, 2011

Login Scripts Fail to Map Network Drives

By D.A.R.Y.L.|2020-02-02T18:16:24+10:00June 16th, 2011|Categories: Windows 7|Tags: Group Policiy, Login Scripts, Network Drives, UAC, Vista, Windows 7|1 Comment

This only applies to you if UAC is enabled and users are a member of the local administrators groups. I was doing some work recently for a client when I noticed that a login script was failing to map network drives if deployed through group policy. The strange thing is that if I ran the script manually it worked. Also, at other sites this same login script works perfectly fine whether it’s run by itself or deployed through group policy. The only difference I could find was that users were local admins at the site where the script fails. When users are local administrators UAC comes into play.

11 06, 2011

DNS Zones Explained

By D.A.R.Y.L.|2020-02-02T18:16:24+10:00June 11th, 2011|Categories: DNS|Tags: DNS|21 Comments

Recently I was doing a bit of promotional work for my blog by participating in some IT related forums. I was going through the post as you do when an interesting question came up. The poster was reading up on about DNS Zones, what their purpose is and how they work. He was having trouble understanding the following paragraph in a study book he was reading: A DNS zone contains all the domain names the domain with the same domain name contains, except for domain names in delegated subdomains. For example, the top-level domain ca (for Canada) has subdomains called ab.ca, on.ca, and qc.ca, for the provinces Alberta, Ontario, and Quebec. Authority for the ab.ca, on.ca, and qc.ca domains may be delegated to nameservers in each province. The domain ca contains all the data in ca plus all the data in ab.ca, on.ca, and qc.ca. However, the zone ca contains only the data in ca (see Figure 2-10), which is probably mostly pointers to the delegated subdomains. ab.ca, on.ca, and qc.ca are separate zones from the ca zone. Can you understand that?? No wonder he was having trouble,

31 05, 2011

How To Open NAT For Xbox 360 And PS3

By D.A.R.Y.L.|2020-02-02T18:17:45+10:00May 31st, 2011|Categories: Xbox|Tags: NAT, open nat, ps3, routers, TCP/IP, xbox, xbox 360, xbox live|10 Comments

To get open NAT on your xbox 360 or PS3 you need to open the ports on your router/NAT and forward them to your console. This can be achieved several ways.

11 05, 2011

Shadow Copy 0x80070005 Access Denied

By D.A.R.Y.L.|2020-02-02T18:17:45+10:00May 11th, 2011|Categories: Windows 2008, Windows 7|Tags: Access Denied, UAC, Vista, Windows 2008, Windows 7|0 Comments

There are different reason why you may get an access denied error 0x80070005. This particular one and the following fix is only applicable when the following is met: Your operating system is Windows Server 2008/Vista. If it is Windows 7 or 2008 Server R2 then this fix does not apply. You have no other problems at all with shadow copies/previous versions. It works perfectly fine accessing previous versions of all other folders except just one (or a few) folders. UAC (User access control) is enabled. More info about UAC can be found here. You are logged in as an Administrator who should be able to access these folders/shadow copies. The error is caused because of a bug in Windows Explorer and how it handles UAC. It is exactly the same reason as to why you get an access denied message when trying to access certain folders you should have access to. In these scenarios you have given the administrators group full control of the folder, you are a member of this group but you still get an access denied message. See the following UAC access denied for the cause and fix. It talks about Explorer having problems accessing certain folders.