Electrical Connection Summer 2016

66 E L EC TR I C AL CONNEC T I ON

SUMME R 20 1 6

GETTING TO THE BOTTOMOF THINGS

omplex and sprawling networks

can be difficult to troubleshoot,

and network professionals

spend approximately 25% of their time

troubleshooting.

NETSCOUT director – APAC channels

Amit Rao says, “Finding the root cause

of network issues is time consuming. If

they’re intermittent issues, it can seem

almost impossible to find and resolve

them. However, by taking a methodical

approach, it’s possible to troubleshoot

enterprise network problems.”

1. INFRASTRUCTURE PERFORMANCE

End user complaints often signify

that there is an infrastructure issue.

However, when application servers and

infrastructure devices are operating

normally, obvious error states can’t be

located and legacy network monitoring

tools report ‘green’. Finding the root cause

can be challenging.

Possible causes include bad cabling,

network congestion, server network

adapter issues or DNS issues.

There are four steps to troubleshooting

these issues:

use existing monitoring tools

and extract information from

SYSLOG receivers.

check server and network device log files

to understand if there are connectivity

issues from the NIC side.

examineWAN links and logs to

understandwhether traffic-shaping

devices or policies are affecting

performance.

check errors including web server, load

balancer, and application log errors.

2. NETWORKSERVICES

There are numerous issues that can

affect network services, such as DHCP

issues or a slow DNS response. Possible

causes include misconfigured DHCP or

DNS servers, duplicate IP addresses

caused by overlapping DHCP scopes, rogue

DHCP servers, or users manually assigning

static IPs. This can enable a ‘man-in-the-

middle’ attack and create significant

security issues.

To troubleshoot, first confirm proper

configuration of authorised DHCP servers.

3. PROVE IT’SNOT THENETWORK

Most of the time, the network is not to

blame for performance issues.

People blame the network due to lack

of visibility into network operations, not

enough bandwidth, network complexity,

insufficient network expertise and lack

of effective troubleshooting tools.

To troubleshoot, you should use packet

captures, gather network data, review

dropped packets, check for excessive

retries and congestion in capture files. You

should also check network device logs and

ping to check response times, as well as

using tracert to verify that the network

path is correct.

4.WIFI ANDBYODTHREATS

WiFi networks, combined with bring

your own device (BYOD) policies, can

create security and performance issues if

not managed carefully. These can include

chatter, dropped connections, excessive

bandwidth issues, and poor device

behaviour from users (such as streaming

music), congestion. The sheer number of

devices can swamp the network.

To troubleshoot, conduct regular WiFi

SSID surveys to detect rogue access points

and routers. Look up MAC addresses to

discover the types of devices attached to

networks and implement MAC address

filtering if necessary. Also, understand

that some devices are well known for

causing problems if improperly configured,

for example, Apple TV Airplay can badly

impact performance.

5. POORWIFI PERFORMANCE

When the WiFi network is

underperforming, network teams should

check for frequency interference, rogue

routers (such as phones being used as

hotspots), misconfiguredWiFi routers, and

compatibility issues between certainWiFi

clients and routers. Even excessive heat

can cause strange symptoms.

To troubleshoot, teams should

regularly use an SSID scanner to

identify rogue routers and APs in

infrastructure, remember that strange

DHCP behaviour is an indicator of rogue

DHCP servers, relocate routers that

may be suffering interference due to

proximity to EMI sources, and ensure

that all WiFi devices are within their

designed operating environment.

6. INTERMITTENT PERFORMANCE

Transient issues can take time and,

sometimes, luck to capture, diagnose, and

resolve. Causes can include cabling issues,

external sources, power fluctuations,

hardware failures and excessive heat.

To troubleshoot, rule out logical

sources, then look for illogical sources of

interference. Track occurrences of the

specific performance issue and look for

patterns. As always, start at the physical

layer, using a cable tester to see if the issue

is related to cabling.

Amit says, “Understanding how to

troubleshoot the most common issues

can reduce the amount of time network

professionals spend on issue resolution.”

> NETSCOUT

www.netscout.com

NETSCOUT

EXPLAINS HOW

TO CONQUER THE SIX MOST

COMMON ISSUES IN THE

ENTERPRISE NETWORK.

TROUBLESHOOTING