Netscout OneTouch AT: quickly discover DNS and DHCP problems

Netscout OneTouch AT

Running a reliable and fast network is not something that just happens. It requires the right tools and the right skill sets to tackle the steps to reduce the number of problems that occur, and when they do occur resolve them in a timely manner. Many problems can be prevented just by taking a few simple steps prior to connecting the network connection to the end device, be it a host computer or a server.

Two of the most basic and critical services on the network are DHCP and DNS. The Dynamic Host Configuration Protocol (DHCP) provides the end device with the addressing information required to communicate on the network and the Domain Name System (DNS) resolves names to IP addresses. If either of these two services stops working or provides inaccurate information, the reachability of devices on the network could be strongly affected. By performing a validation test at the time of installation, any problems with these services can be resolved before the end device is connected.

The NETSCOUT OneTouch AT Network Assistant provides a simple and easy way to validate DHCP and DNS services. Regardless of copper, fiber or wireless interfaces, the OneTouch AT is capable of validating these critical services on any of the physical layer technologies found in a corporate environment. This allows one set of tests to be developed and used consistently across all of these technologies.

While a laptop could be used to grab an IP address via DHCP and ping a DNS server, the issue comes when that ping times out. Is it a problem with the VLAN? Which switch and port are we using? The OneTouch AT provides all of this information as part of the AutoTest feature. While running the basic service tests, the OneTouch AT checks for the presence of Power Over Ethernet (PoE) and measures the voltage. It listens for Cisco Discovery Protocol (CDP) and Link Layer Discovery Protocol (LLDP) to determine the switch and port. If these are not available, it will use Simple Network Management Protocol (SNMP) to determine the switch and port. In a Wi-Fi environment, the OneTouch AT will provide information about the Access Point, signal strength, and cross-channel interference. For fiber, the device can measure the optical signal strength. [feature_box style=”14″ only_advanced=”There%20are%20no%20title%20options%20for%20the%20choosen%20style” top_margin=”3″ bottom_margin=”5″ top_padding=”3″ bottom_padding=”3″ alignment=”center”]

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The vast majority of the time, the validation test will show that things are working properly. In this case, we can click a button, generate a report, and move on. When things aren’t working, we need as much information as possible to get to the root of the problem.

What can go wrong with DHCP? One of the most common problems is rogue DHCP server. This occurs when someone connects a router with a DHCP server to the network. This can be a very difficult one to troubleshoot since it requires tracking down the offending device. With the OneTouch AT, we can use the Path Analysis feature to locate the switch and port where the router is connected and shut it down. Without that information, we would be crawling under desks, tracing cables to unmarked switches, and logging into the switch to determine the location of the device.

Verifying DHCP and DNS is just the beginning of the tests that can be performed with the OneTouch AT. With a click of the screen, tests can be added to check websites, file services, custom TCP ports, and throughput. By developing and using these test profiles to validate connections, you will be well on your way to maintaining a reliable and fast network.

Lisa Schwartz

Lisa Schwartz

Lisa Schwartz is the Sr. Product Manager for LinkRunner AT, LinkSprinter and Link-Live Cloud Service and is currently based in Colorado Springs, CO. Lisa has worked in the Test & Measurement field as product manager, business development and product marketing since 1992 at Microtest, Inc., Datacom Textron, Fluke Networks, Visual Network Systems, and currently with NETSCOUT Systems.

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