2015 年 9 月 11 日
Experiencing speed and performance issues with the WAN? There are multiple potential causes, but how can one go about isolating the true cause quickly and easily? Here is a series of steps to help restore WAN to its optimal speed and performance in no time.
|Begin troubleshooting by checking the most basic, simple things. Then work upwards in terms of complexity and probability (or how likely that item is to cause problems with the WAN).|
1. Check the Speed of the Router and Switch Ports
This seems like a no-brainer, but it's sometimes too easy to overlook the basics. Check to see that the speed and duplex of the router and switch ports are configured the same. This is usually governed by automatic negotiation, but that doesn't always work as it should. Never assume that a 10/100/1000 port is properly auto-negotiating.
2. Use Monitoring Tools
In order to troubleshoot a WAN, it is imperative to know whether the issues are totally random or if the problems occur at predictable intervals. Some problems are consistent and leave a clear trail of evidence to make it easy to find the problems. Other issues can be intermittent, with no clear cause at all. Only with the right monitoring tools can network administrators determine which type of issues they are dealing with.
3. Check the Settings and Configurations of the WAN
Other frequently seen issues involve the configuration of things like Class of Service on the WAN or DSCP on a LAN, or perhaps the mapping of the DSCP values to the Class of Service. Check the settings and configurations before assuming that the problem is more serious, such as a hardware failure.
4. Verify Whether the Issues Affect All Applications the Same
Sometimes, the issue can affect a particular application or type of application, while all of the other applications experience no issues at all traveling the WAN. Again, good monitoring tools can be extremely helpful. Check to see whether the problems are related to any certain application or type of application.
5. Verify if Any of the MPLS Ports Are Becoming Saturated
WAN issues can also be the result of bandwidth utilization. Check the carrier's web portal to see if the MPLS ports of any particular locations are becoming saturated, even for very short periods of time. This is often the result of transferring huge files, such as CAD drawings or large videos.
6. Determine Whether System Backups are Indeed Completed Before the Workday Begins
As systems and networks grow and mature, the time it takes to complete backups grows, too. Sometimes it is possible for backups that begin at midnight to run past the time when workers arrive and begin their productive mornings. This is especially true in workplaces where there is a significant number of remote workers accessing the network. It might be necessary to bump back the time that system backups start, say to 9 or 10 pm instead of midnight to allow the backup to complete before workers begin logging in. Data synchronization activities are another possible cause.
7. Check the Routing Tables
|Usually, examining the trends and patterns over the past two weeks of WAN activity is sufficient to determine a pattern that will showcase any issues causing problems.|
It is also possible that routing activities are taking multiple paths instead of using the most direct possible path. Take a look at the routing tables to see if this could be causing some speed issues.
8. Look at the Long Term Activity Trends & Statistics
If the above steps fail to produce an answer to the WAN problems, look at the longer term trends. Usually it is sufficient to go back a couple of weeks into the statistics. Check the SNMP streams from each individual router until it becomes evident where the problem is coming from.
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