Checking Connectivity: Ping Me, Ping You
It’s 4 p.m. Friday, when several users call the help desk to complain that their e-mail isn’t working. You check the e-mail server, and everything looks fine. Where does the problem lie? Just because you have no trouble connecting doesn’t mean that the problem is user error. Typically, smaller networks don’t have a sophisticated monitoring utility. Even mid-sized environments may not have mechanisms that notify an on-call engineer when datagrams hit the proverbial bit bucket.
Nearly worth its weight in precious metal is WhatsUp Gold 8.0 (www.ipswitch.com) and its add-ons, a clever WAN-aware utility that is capable of monitoring connected segments and ports, providing various notifications, monitoring based on recorded system events and TCP/UDP service monitoring, mapping and discovery. Available in several versions, the premium solution boasts SQL Server and Exchange monitoring capability, but a newer, less expensive option for small businesses has only slightly fewer features (it is also limited to 10 hosts) and is upgradeable to the full version. What makes WhatsUp Gold (WUG) so compelling is the mapping combined with a color-coded display showing segments and activity, as well as a host of additional features: network tools, Web control (monitoring and notification) and reporting with some trend analysis. WUG has gone way beyond its original incarnation as a mostly ping utility on top of graphical network displays. Newer features include enhanced SNMP reporting and a failover provision.
Of course, there are WUG competitors, and some of them are nearly free. N-View (www.n-view.de) signals network changes and maps by discovering hosts and subnets. IPCheck Server Monitor is available at www.paessler.com. Though IPCheck was initially designed to monitor Web servers, a new version will monitor multiple types of servers.
What if you don’t have any monitoring utility? There are always the environments where even return on investment (ROI) arguments won’t merit consideration for preventive utilities. You may have to use the tools available through your network operating system (NOS). In some cases, that would be your first troubleshooting step—to verify IP connectivity, you ping the destination. A good primer on how to use ping and other tools to troubleshoot can be found at www.svrops.com/svrops/documents/tcpip.htm. Microsoft’s site offers guides to using netstat, nbtstat, arp, nslookup and others—search on “Using Graphical Administrative Tools.” The ’Net abounds with enhanced pings, but a good collection can be found at compnetworking.about.com/cs/pingtools. For other useful tools, see www.snapfiles.com/Shareware/network/swtraceroute.html. Some utilities herein combine functions, such as traceroute and ping, whereas others offer graphical displays.
Since Active Directory is based on a properly functioning DNS, simple steps may yield a solution to an otherwise intractable problem. Other DNS problems may arise for obscure reasons: We had a ’Net address blacklisted because of a previous owner. A favorite site to help track how the world sees your addresses is www.dnsstuff.com. Along the same lines, Network-Tools.com does nslookup and whois. On the Novell side, understanding the communication between servers is key—among native utilities, dstrace and tcpcon are generally underutilized. To use a more automated approach, try an inexpensive tool to monitor NetWare servers and other NOSs, such as GFI Network Server Monitor (www.gfi.com).
One of my favorite troubleshooting tools can be found at www.ixiacom.com, and is free for the registration. QCheck 3.0, originally by NetIQ, requires that performance endpoints be installed on the two computers to test, although one endpoint is built in to the monitor. QCheck can run several tests, including throughput, response time, streaming traffic rate and traceroute, which doesn’t need the endpoint installed at the target. QCheck is much better at simulating traffic flow for very common protocols than ping, though it lacks the flexibility of its bigger, more expensive brother, Chariot. Using QCheck, you can also show a workstation’s CPU utilization, memory and OS level.
Learning what tools your OS has to verify connectivity is a major part of troubleshooting failed connections. If you can’t afford enterprise monitoring utilities and hardware, there are good alternatives, from shareware to inexpensive commercial products. Lookup tools on the ’Net and enhanced utilities that are freely available should be a part of your front-line toolkit. Learning how to use these tools efficiently is what will distinguish you as a competent network administrator.
Douglas Mechaber, MCSE, MCNE, CCNA, BCSD, is always looking for cool utilities to make his job easier at a large, government health organization. Send him your favorite utility listing or comments at firstname.lastname@example.org.