Thursday, August 30, 2012

Error 1231 On Windows Vista

Error 1231 is a network problem that occurs due to connectivity problem or network trouble shooting. When this problem occurs, the information displayed on the screen is; - ‘location network cannot be reached'. Due to this problem, physical computers are unable to connect to the Internet.

Error code 1231 is associated with Windows Vista. Once it occurs, one cannot ping his or her own IP or default gateway because once one tries to ping this gateway the resultant error reads, ‘ping transmit failed error code 1231 message. When this problem occurs and that one is using V6, try deselecting TCP IP V6 setting under the LAN adapter. This seems to favor V6 over V4 since it is thought that this could cause the problem.

The error message suggests you have a problem with the IP configuration, settings, or with TCP/IP. To fix it reset the TCP/IP stack, below is the process on how to reset the TCP/IP Stack when error 1231 appears:

Go to the Start Menu, type cmd and right click or (Ctrl + Shift and hit Enter), and select "Run As Administrator"
Type the following commands, each followed by pressing enter. § ipconfig /flushdns
nbtstat -R
nbtstat -RR
netsh int reset all
netsh int ip reset
netsh winsock reset
Test connectivity, is the customer able to surf.
Second Fix Process if the first does not work:

Open an elevated command prompt.
Once at the command prompt, type: netsh int ip reset iplog.txt.
NOTE: The last part of the command: "iplog.txt," is the filename of the logged results of the command if you want to view it.

Wednesday, August 29, 2012

Understanding IPv6

What is an IP address?

IP, which stands for Internet Protocol, works like a street address to pinpoint exactly where you are accessing the Internet from. This allows information, like web pages and email, to be delivered to you. Every device (such as a mobile phone, a Wii, a PlayStation console or a computer) that accesses the Internet must have a unique IP address, which is generally provided by an internet service provider like Time Warner Cable and AT&T. Without an IP address, a device will not be able to get to internet to send and receive information.

An IP address is a unique number that identifies the location of a computer or device on a network. The current IP address version is called IPv4 and a typical public IP address looks like this:

What is IPv6?

IPv6 is the abbreviation for Internet Protocol version 6. We are currently on Internet Protocol version 4, or IPv4, but IPv6 will be the next generation protocol for Internet communication. Not only will IPv6 provide a much larger address space, but it will also provide features such as improved routing traffic and better security.

What does an IPv6 address look like?
An IPv6 address is much longer than an IPv4 address and looks something like 24da:db8:ac10:fe01:2aa:ff:fe00:56ab.

Here are a few characteristics of IPv6:
1. IPv6 contains a combination of both letters and numbers (0 through 9, and A through F).
2. IPv6 consists of 32 hexadecimal characters in an address and is 128 bits in length.
3. An IPv6 address could look like this: fd98:d3e2:f0fe:0:54ae:34ff:fecc:892, compared to an IPV4 address that looks like this:

What is the difference between IPv4 and IPv6 addresses?

An IPv4 address is a series of 4 numbers separated by periods. An example of an IPv4 address is
An IPv6 address is a series of 8 numbers separated by colons. An example of an IPv6 address is 2001:db8:ac10:fe01:2aa:00ff:fe00:56ab.

Why do we need IPv6?

The Internet has experienced a phenomenal increase of devices accessing the Internet. Because of this increase, IPv4 addresses are running out. The solution is for IPv6 to accommodate this increased demand by providing a much larger address space, along with improved traffic routing and better security.

Some of the major advantages of IPv6 are:

1. Larger IP address space: IPv6 has 128-bit address space or 4 times more address bits compared to IPv4's 32-bit address space. This large address space will provide enough address space for many decades to come.
2. Better security: IPv6 includes security in the underlying protocol. For example, encryption of packets (ESP: Encapsulated Security Payload) and authentication of the sender of packets (AH: Authentication Header).
3. Consideration to real time: To implement better support for real-time traffic (such as videoconference), IPv6 includes a flow label mechanism so routers can more easily recognize where to send information.
4. Plug and play: IPv6 includes plug and play, which is easier for novice users to connect their machines to the network. Essentially, configuration will happen automatically.
5. Better optimization: IPv6 takes the best of what made IPv4 successful and gets rid of minor flaws and unused features.

Why can’t IPv4 just be expanded?
There were many proposals regarding how to solve the problem with the availability of IPv4. The Internet community agreed that the approach of IPv6 is the best.

If we run out of IPv4 addresses, will that mean I will not be able to connect to the Internet?
No, you will still be able to connect to the Internet as you normally do.

Will I need to purchase new equipment to support IPv6?
Your computer probably already supports IPv6, but you should upgrade to the latest version of your operating system and browser. Most network-capable consumer electronics don’t use IPv6 yet, but may with a future software or firmware update. 

Will mobile and wireless devices work on IPv6?
Yes. Mobile and wireless devices will work with IPv6.

Is there any way for me to check my IPv6 readiness?
Yes. But call your internet service provider.

Websites that also provide general IPv6 information include:
The Internet Society -
The American Registry of Internet Numbers -
Wikipedia -

Monday, August 27, 2012

TCP/IP Utilities

Utility is a program or application that enhances an operating system's capabilities by performing a special function not provided by the operating system, such as a "print" utility or a "search and replace" utility.  There are three common TCP/IP utilities: Ping, Tracert, and NSlookup, which are available on both a Macintosh and Windows-based computer.

These utilities will help you diagnose and troubleshoot issues by verifying:

(PING) That a specific IP address or URL is active and also able to send/receive information

(TRACEROUTE) That a route/switch that could be causing an issue is identified

(NSLOOKUP) Who hosts the domain, either by IP address or URL

This command verifies that a specific destination IP address exists and is operating (i.e., accepting requests).  Ping works by sending an echo packet to a specified host and waiting for a reply.  All hosts are supposed to bounce the packet back so that the program can determine if the host is online or not.

Ping can also be used to:

1. Determine how long it takes to receive a response from a specific address (to calculate latency)

2. Determine a host's dot address.  Ping will not help if you are having any non-connectivity related problems with applications like Microsoft Office, etc.

The IPv4 syntax for the ping command is: ping [destination computer or IP address] and the IPv6 syntax for the ping command is: ping6 [destination computer or IP address]

You can set any of the following options when using the ping command:

-n – Specifies the number of packets to transmit.  Default is four.  In the example below, the ping count is 10.

-a – Resolves IP addresses to host names.

-l (Lowercase "L") – The size of the packet being transmitted (default is 32 bytes).  In the example below, the packet size is 50. 

NOTE: The larger the packet, the longer it takes to get a reply. 
 -t – Used for a number of things, such as detecting if the customer has a firewall.  This command will ping an IP address continuously until you press CTRL-C.  To determine if the customer has a firewall, run the command while the customer reboots the PC.  If a firewall loads, the ping replies will stop (unless you press CTRL-C). 

Tracert is a diagnostic utility used to identify equipment issues.  It traces the route taken to a destination by sending echo packets with varying Time-to-Live (TTL) values.  For example, we may only set the TTL to 10 hops.  This tells us the number of hops that a packet of information makes from one point to another in the network.  Each router/switch encountered along the path decreases the TTL value by 1 before forwarding it.  So, if the max TTL is set to 10 hops, it will count down from 10 to 9 and so on until it either is at 0 or finds the piece of equipment it was tracing to. 

When the TTL on a packet reaches 0, the router is supposed to send back a Time Exceeded message. Some servers just drop the request without sending back a message, or they block the packets and return a "Request Timed Out" message. In this case, a row of asterisks (*) is displayed. Tracert determines the route by sending the first echo packet with a TTL of 1 and incrementing the TTL by 1 on each subsequent transmission until the target responds or the maximum TTL is reached. The route is determined by examining the ICMP Time Exceeded messages sent back by intermediate routers.

NOTE: While tracert is an effective tool used to determine the path to a destination site, it is not always the best tool for determining packet loss or latency along that path. Because of the way that tracert works (it only pings each hop three times, therefore providing a very small sample of data), the times listed at each hop may give an inaccurate representation of the status of the network. Ping is a much more effective tool for determining packet loss and latency.

NOTE: The first column is the hop number.  The next three columns show ping times between you and that particular host.  The last column shows the name of that server, or gateway, and its IP address.

A few important facts about Internet speeds related to latency:

Hop times of less than (<) 100 milliseconds are normal for short (<100 distances.="distances." medium="medium" miles="miles" p="p" to="to">

Hop times of <200 although="although" applications.="applications." cause="cause" distances="distances" do="do" for="for" ideal="ideal" in="in" longer="longer" miles="miles" milliseconds="milliseconds" most="most" not="not" p="p" problems="problems" the="the" us="us">

Sustained, consistent hop times greater than (>) 250 milliseconds need to be investigated. Occasional response times of >250 milliseconds do not need to be investigated (these occur due to momentary network congestion). 

The Traceroute command line syntax is:

tracert [-d] [-h maximum_hops] [-w timeout] target_name >> textfile.txt

Traceroute Command Line Options:

-"d" – Does not resolve addresses to hostnames. 

-"h maximum_hops" – Maximum number of hops to search for target. 

-"w timeout" – Wait timeout milliseconds for each reply. 

">> textfile.txt" – Writes the results to textfile.txt in the same directory you run tracert from. 


This diagnostic tool displays information from the DNS name servers.  You can enter a host name and find the corresponding IP address.  You can also enter an IP address, and the corresponding host name will be displayed.  This is known as a "reverse lookup".

The command line for NSLookup is:

C:> nslookup [domain or IP address]

NSLookup Command Line Result
NSlookup by URL: 

When starting NSLookup, you may receive the following errors:

Can't find server name for address example: w.x.y.z Timed out.

NOTE: w.x.y.z is the first DNS server listed in the DNS Service Search Order list.

The error indicates that no servers have been defined in the DNS Service Search Order list.  To correct this problem, add the IP address of a valid DNS server to this list.

Can't find server name for address Timed out

This error indicates that the DNS server cannot be reached or the service is not running on that computer.  To correct this problem, either start the DNS service on that server or check for possible connectivity problems.