November 10th, 2009 -- Posted in Other |
Overview
The process of troubleshooting your network if it has wireless components is somewhat more complex than wired infrastructure. In fact you must troubleshoot both wired and wireless infrastructure to determine the problem. The methodology of starting with cabling from the client and working through the OSI model to the application layer is effective. The wireless client traffic doesn’t see any cabling until there has been association with the access point. In essence there is a data link between wireless client and access point. With that established there is data link traffic between access point and wired network switch.
The wired client has a Cat 5 cable plugged into the desktop that terminates at a wired switch. All clients associating at a specific access point now share a single Cat 5 cable run from access point to switch. That makes troubleshooting easier since cabling is a source of a lot of network problems, however any problems with that cable affects all clients. It is important to minimize the number of access point clients for maximum performance. Commercial network implementations average 10 – 24 clients per access point.
The key with troubleshooting is to determine what has changed. Sometimes it is hardware that isn’t working or some change made such as new software, configured equipment or additional employees stressing the network. It could be a specific issue or several problems. Start with the client adapter, determine the specific symptoms and go from there.
The following is a series of questions that can used as a guideline during the troubleshooting process:
1. Can the wireless client associate with any access point?
2. Can you ping the switch IP address?
3. Can you ping the router?
4. Can you ping the DHCP server?
5. Does the client obtain an IP address?
6. Is the WAN circuit available?
7. Has new software been installed on the client?
8. Do all clients experience the problem?
9. Is it random or a specific pattern?
10. Is it server specific or application specific?
11. Is the DNS server IP address setting correct?
12. Is there a firewall that is filtering traffic?
TOOLS:
a) Wireless client software shows status information such as access point association, DHCP enabled, IP address, default gateway, DNS server address.
b) Windows control panel shows wireless adapter settings, firewall configuration etc.
c) Ping will verify that network routing is working.
d) Network packet sniffers examine packet information such as protocols, filtered programs or errors with applications.
e) Spectrum analyzers detect frequency interference and possible sources.
COMMON WIRELESS PROBLEMS:
Wireless Client Settings
• Upgrade the manufacturer client adapter driver.
• Implement current Windows operating system service pack.
• Examine client data rate, transmit power, preamble, roaming decision, WPA settings.
• Confirm shared keys if implemented aren’t mismatched between client and AP.
• Examine IP address settings. DHCP will send specific settings to each client. Those clients without DHCP must configure IP address, subnet mask, default gateway and DNS server IP address.
• The client SSID name configured should match what is configured at the AP.
Access Point
• Confirm the APs have the recommended IOS version with the specific feature set.
• Examine AP mounting and modify if necessary using the installation instructions.
• Delete any configured loopback addresses.
• Configure transmit power setting and decrease when channel interference occurs.
• Mixed 802.11b/g environments must configure each AP with 802.11b basic data rates.
• Configure data rate and duplex settings to match between AP and switch.
Design
• Configure data rate and duplex setting to match between wireless bridges.
• Standard Cat 5 UTP cable should be a maximum of 328 feet between AP and switch.
• Distance from the wireless client to access point should not exceed the specified range.
• Maximum number of clients per access point should not exceed 17 – 24.
• Don’t assign channel overlap between neighbor APs.
• Configure spanning tree protocol at root bridges
• Configure non overlapping channels of 1, 6 and 11 at 802.11b and 802.11g APs.
• Don’t configure multiple root bridges on the same WLAN
• Implement the most current version of Windows Server, IAS RADIUS Server or Cisco ACS
• RF interference will occur in an unlicensed band. Minimize sources where possible.
Cisco Wireless Network Design Guide available at amazon.com and eBookmall.com
Shaun Hummel is an author of various technical books and has a web site focused on information technology job search solutions and certifications.
http://www.networkjobsolutions.com
Shaun Hummel, CCNP, is a Senior Network Engineer with 11 years experience in enterprise network planning, design, and implementation. He has worked for various private and public companies in Canada and the United States improving infrastructure, security, and management. He has written Network Planning and Design Guide, Cisco Wireless Network Design Guide and Network Assessment Guide.
www.networkjobsolutions.com
November 10th, 2009 -- Posted in Other |
Overview
The process of troubleshooting your network involves a methodology that starts with cabling and works through the OSI model to the application layer. The network devices have a network cable that terminates at a wired switch. Cabling is a source of a lot of network problems.
The key with troubleshooting is to determine what has changed. Sometimes it is hardware that isn’t working or some change was made such as new software, configured equipment or additional employees stressing the network. It could be a specific issue or several problems. Start with the client adapter, determine the specific symptoms and go from there.
The following is a series of questions that can used as a guideline during the troubleshooting process:
1. Can you ping the switch IP address?
2. Can you ping the router?
3. Can you ping the DHCP server?
4. Does the client obtain an IP address?
5. Is the WAN circuit available?
6. Has new software been installed on the client or server?
7. Do all clients experience the problem?
8. Is it random or a specific pattern?
9. Is the problem server specific or application specific?
10. Is the DNS server IP address setting correct?
11. Is there a firewall that is filtering traffic?
12. Ran traceroute and examined routing behaviour?
TOOLS:
1) Windows control panel shows network adapter settings, firewall configuration etc.
2) Ping and traceroute will verify that network routing is working.
3) Examine the ARP table on the desktop, switch and router confirming the device MAC address is there.
4) Network packet sniffers examine packet information such as protocols, filtered programs or errors with applications.
5) Verify change management activities and determine what if any device was changed and how.
6) Show interfaces at the router will reveal any interface errors pointing to a cable or hardware problem.
7) Examine router interface utilization patterns.
Working from the cable level and determining if the problem is affecting a single user, a department, building or city wide is a good place to start. A city wide problem sometimes indicates a data center outage. A building sometimes points to a circuit, router or primary switch. A department can indicate a problem with their network switch or fiber cabling. The single user problem could be a myriad of issues from a bad cable to network permissions. Because companies have in some cases hundreds of applications, network switches and routers the problem becomes more complex when it is a cross department issue. Not all employees have the same network permissions and use a variety of applications across departments, cities and countries.
Determining who is affected by the problem can be a key factor in resolving the issue. The ping is a popular tool since it verifies to the network layer all is working. In that case your then focusing on application issues although not always. Traceroute verifies how packets are traveling between source and destination. You could have packets using non optimal routing paths that are causing performance problems.
Network Planning and Design Guide is available at amazon.com and eBookmall.com
Shaun Hummel is an author of various technical books and has a web site focused on information technology job search solutions and certifications.
http://www.networkjobsolutions.com
Shaun Hummel, CCNP, is a Senior Network Engineer with 11 years experience in enterprise network planning, design, and implementation. He has worked for various private and public companies in Canada and the United States improving infrastructure, security, and management. He has written Network Planning and Design Guide, Cisco Wireless Network Design Guide and Network Assessment Guide.
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November 10th, 2009 -- Posted in Other |
When your work implicates receiving different important e-mails but your address is full with spam e-mails, you cannot be happy with that. You can even miss important information because it is misinterpreted as spam. The problem is that you can open these mails by mistake and corrupt your own computer without notice. This is the reason why using an antispam appliance is given so much importance. However, if you have considered using protection appliances, you should know that the best way to start is with a penetration testing application.In order to prevent spam e-mails, you must first detect these messages. A method of doing this is to determine the content of the e-mails by searching for different keywords or referring to statistical means. There are also different lists of IP addresses from where spam e-mails are sent to people. But these are sometimes pretty difficult to set without professional help. For this reason, different products, services, software programs as antispam appliance are developed, enabling people to safely open their e-mail addresses.Companies, institutions, individuals have now the possibility to buy an Unified Threat Management application – UTM, as a protection unit and antispam appliance, recommended for all the possible threats. It is an all-in-one application and a single device can protect a whole network of 5 until 500 users. It is a really useful application, because it is just one single device with a plug and play architecture unit. Under circumstances, it works like antispam appliance, antivirus, firewall, content filter, application against worm’s attacks, etc. It is a very effective tool for guaranteeing the complete protection of computers.The penetration testing application is a really helpful method used to protect computers. It can be used for each IP address and it offers a report, showing the level of risk for each computer. In this way, each IT system is scanned and checked for all the vulnerabilities that can be used to breach the security appliances. Therefore, every router, firewall, operation system, any application with IP address can be checked and a report with two parts will show all the potential problems found in the system. The advantage of the penetration testing application is that not only it shows you the security vulnerabilities of your network, but it also gives you the alternatives and solutions to repair these issues. It also gives you the possibility with the technical output from the second part of the report to reproduce the path of attack, so you can understand how it works. Another advantage is that you can schedule for regular and self-acting scanning. In this way, you can compare data from different reports, so you can see if your security level is rising or falling down.It is understandable why penetration testing application and antispam appliance mean so much for the good unfolding of activities in a company. These are powerful tools to prevent potential losses and wasting precious time with unwanted e-mails. More powerful attacks mean more powerful security applications. So, when it comes to protecting your hard work, security measures are never too many.
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