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Traceroute- A Networking Tool

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Traceroute is a utility that send an ICMP packets from our computer to user input destination and displays information about what is happening to the packet on each point along the path.

Traceroute- A Networking Tool

  1. 1. NETWORKING TOOL TRACERT/TRACEROUTE Introduction Traceroute is a utility that send an ICMP packets from our computer to user input destination and displays information about what is happening to the packet on each point along the path. The path displayed is the list of near-side interface of the routers between a source host and a destination. It also calculates and displays the amount of time each hop took. Hops are nothing but the computers, routers, or any devices that comes in between the source and the destination.
  2. 2. Purpose of Traceroute The purpose of traceroute is to identify the problematic server that is causing the error, and that is why we send traceroute info only if there is an error before reaching our servers. Traceroute is a very resource consuming operation and it will slow down our servers a lot if we do it all the time. Network administrators and system administrators use this tool most commonly in their day to day activities. Types of Traceroute Program There are different types of traceroute programs. Each of them works slightly differently. But the overall concept behind each of them is the same. All of them use the TTL value. The different types are mentioned below. 1) UDP Traceroute- It’s the default protocol used by Linux traceroute program. However we can also use ICMP instead of UDP by giving the below command in Linux. root@workstation:~# traceroute -I -n 8.8.8.8 2) ICMP Traceroute- ICMP for traceroute works the same way as UDP traceroute. Traceroute program will send ICMP Echo Request messages and the hops in between will reply with a ICMP Time exceeded messages. But the final destination will reply with ICMP Echo reply. Tracert command available in windows operating system by default uses ICMP traceroute method. 3) TCP Traceroute- Its used because almost all firewall and routers in between allows you to send TCP traffic. And if the packet is toward port 80, which is the web traffic then most of the routers allow that packet. TCPTRACEROUTE by default sends TCP SYN requests to port 80. Objectives of Traceroute ● Traceroute determines how packets are being routed to a particular host. ● It also helps in determining the entire path that a packet travels through ● Determines names and identity of routers and devices in your path ● Helps in determining the Network Latency or more specifically the time taken to send and receive data to each devices on the path ● It is useful in determining where a network outage is occurring, test connectivity and determining congestion in traffic.
  3. 3. ● Traceroute is a handy tool both for understanding where problems are in the Internet network and for getting a detailed sense of the Internet itself. ● TRACERT is useful for troubleshooting large networks where several paths can lead to the same point or where many intermediate components (routers or bridges) are involved. How Traceroute Works When we connect to a website – say, google.com – the traffic has to go through several intermediaries before reaching the website. The traffic goes through our local router, our Internet service provider’s routers, onto larger networks, and so on. Traceroute shows us the path traffic takes to reach the website. It also displays the delays that occur at each stop. If we’re having issues reaching a website and that website is working properly, it’s possible there’s a problem somewhere on the path between our computer and the website’s servers. Traceroute would show us where that problem is.
  4. 4. In more technical terms, Traceroute sends a sequence of packets using the ICMP protocol. The first packet has a time-to-live (also known as TTL, or hop limit) of 1, the second packet has a TTL of 2, and so on. Each time a packet is passed to a new router, the TTL is decreased by 1. When it reaches 0, the packet is discarded and the router returns an error message. By sending packets in this manner, traceroute ensures that each router in the path will discard a packet and send a response. Traceroute Command The tracert command is CMD command that's used to show several details about the path that a packet takes from the computer or device you're on to whatever destination you specify. It also sometimes referred as the traceroute command. Tracert Command Syntax The command for Unix systems is traceroute, whereas on Linux systems the command is tracepath and current windows base systems used the command tracert. Syntax tracert [-d] [-h MaxHops] [-w TimeOut] [-4] [-6] target [/?] ● -d = This option prevents tracert from resolving IP addresses to hostnames, often resulting in much faster results. ● -h MaxHops = This tracert option specifies the maximum number of hops in the search for the target. ● -w TimeOut = You can specify the time, in milliseconds, to allow each reply before timeout using this tracert option. ● -4 = This option forces tracert to use IPv4 only.
  5. 5. ● -6 = This option forces tracert to use IPv6 only. ● target = This is the destination, either an IP address or hostname. ● /? = Use the help switch with the tracert command to show detailed help about the command's several options. How to Use Traceroute Suppose we want to do a traceroute to Google’s publicly available DNS server (8.8.8.8). My traceroute command and its result will look something like the below. tracert 8.8.8.8 When we fire that command of tracert 8.8.8.8, my computer makes a UDP packet. This UDP packet will contain the following things. 1) My Source Address (Which is my IP address) 2) Destination address (Which is 8.8.8.8) 3) And a destination UDP port number which is invalid. Means the traceroute utility will send packet to a UDP port in the range of 33434 to 33534, which is normally unused.
  6. 6. Save the tracert output in a text file as follows: 1) Right-click the title bar of the Command Prompt window and choose Edit > Select All. 2) Right-click the title bar of the Command Prompt window again and choose Edit > Copy. 3) Open the Windows Notepad program: Windows Start icon > All Programs > Accessories > Notepad. 4) To paste the output into Notepad, choose Edit > Paste. 5) Choose File > Save As and save the Notepad file to your desktop as tracert1.txt. Traceroute session may be stopped by pressing [Ctrl]+[C]. Note: - The tracert command is often used with other networking related Command Prompt commands like ping, ipconfig, netstat, nslookup, and others. Thank You

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