Network Issues

Network Issues

There are some other network issues which are discussed as follows:

  Name not resolved 

ERR NAME_NOT_RESOLVED i.e. the name not resolved error usually appears when a user tries to access a website. An error message is displayed on the screen which shows the web page is not available. It simply means cannot to that website. A possible reason can be that the browser cookies have blocked a user’s Internet DNS. However, try to delete browser cookies to resolve this issue.

Incorrect Gateway

While troubleshooting network services, a user may encounter a problem in which the system displays error the default gateway is not available. This error generally appears when a user tries to access any website. Further, it might be possible that the Internet connectivity shows limited access. However, a user can resolve such issues by assigning the default gateway and IP address manually.

Incorrect Netmask

The subnet mask can be defined as the 32-bit number which enables the receiving node to identify the network and host address. Further, it identifies the network on which a user is working. Thus, if a user has incorrectly configured a subnet mask, then the system will generate an error and the Internet connectivity will get affected.

Duplicate IP Addresses Duplicate

IP address is a situation where two devices in the same network have similar IP addresses and it is generally termed as IP address conflicts. One way to detect the presence of duplicate IP address is sending ARP packets to that IP address. Thus, all the systems with the same IP will reply with the MAC address and then a duplicate IP address can be easily detected. In addition, Nmap, a powerful network scanning tool, can also be used to detect users having duplicate IP addresses.

Duplicate MAC addresses

MAC address can be defined as the. Physical address any network device such as a router, switch and laptop. It might be possible that two hosts or devices have the same MAC address due to spoofing. If their exit two devices with the same MAC address, the switch will update its MAC table every time it receives a packet from either host and this will affect the performance of the network.

Expired IP address

A DHCP server keeps record of time (referred as lease time) while assigning an IP address to a device. Thus, a client can only use the given an IP address for a limited period and it expires once the lease period gets over.

Rogue DHCP server

A rogue DHCP server are set up by the cyber attackers or unauthorised user and are not maintained by the administrative department of the organization An IDS (Intrusion Detection System) can be used to detect and disable rogue DHCP servers. In addition, there are some other software available to detect rogue DHCP servers such as Microsoft Network Monitor 3.4, soft perfect Network Scanner, Rogue Detect and DHCP Sentry.

Untrusted SSL Certificate

An error such as SSL certificate for this website is not trusted occurs when a user tries to access a SSL enabled website without establishing a secure connection with the server of the website. Thus, a warning message gets displayed on the browser screen such as “This connects is untrusted” or “The site’s security certificate is not trusted”.

Incorrect Time

If a system displays incorrect date and time the following steps can be taken to update date and time settings of the system:

  1. Click on the date and time on the Taskbar, and then click on date and time settings.
  2. A dialog box will appear on the screen. Select Date and Time tab, and click on the Change date and time
  3. Now, a dialog box will appear on screen where a user can update date and time settings of his system.

Exhausted DHCP scope

An exhausted DHCP scope indicates that the specified address range has An e  already been allocated to the network devices and no more address value is available to be assigned. To resolve this issue, DHCP scope needs to be recreated with the sufficient number of IP addresses. Further, DHCP address pool can be viewed and managed with the help of DHCP manager utility. This utility can be accessed from the tool option available in the server manager.

Blocked TCP/UDP Ports

Ports are the logical connection between two computers or network resources which are used for data transmission. A user can easily determine which ports are open and blocked on his system with the help of port scanning tools. Some commonly used port scanning tools are Nessus, Nmap and OpenVAS. In addition, a user can also perform a port scan on Windows with the help of Microsoft command line utility. For example, to test a specific port, following command can be used:

portqry.exe -n 192.168.1.1 -e 80

This command may generate an output such as TCP port 80 (http service): NOT LISTENING. It means that there is no response from the destination and output indicates that either the port is blocked or not working properly.

Incorrect Host-Based Firewall Settings

Host-based firewall provides security against threats such as viruses and worms. It also controls network traffic from public networks. Incorrect host-based firewall configuration results in a security breach which may lead to malware invasion in the entire network. Further, this can affect all the computer systems connected to the network.

Incorrect ACL settings

ACL (Access Control List) contains two types of statements namely, permit • and deny which are used to manage data traffic coming in and out of the network.

A user needs to be careful while configuring ACL and its associated rules as ACL is placed right at the firewall’s interface. Incorrect ACL configuration causes not only network issues but any unwanted data or malicious code may also get into a network.

Unresponsive service

There are some conditions which may arise due to unresponsive services such as timeouts, terminated sessions, and data loss. Thus, it is important that each application and its dependent services as well as the drivers should respond to system power and shutdown notifications.

In order to respond appropriately to system shutdown notifications, each application must generate a prompt message such as WM_ QUERYENDSESSION and WM_ENDSESSION to specify that a shutdown is in progress.

The system initiates a time-out of 20 seconds for each process to respond. If any process or service fails to respond in time to system shutdown notifications, the system stops and declares such service as unresponsive. Further, a system also adds 20 seconds to the shutdown time. Thus, services having device driver dependencies must respond to IRP MJ SHUTDOWN notification in their DispatchShutdown routines.

Hardware failure

A network cannot continue to operate in case of a hardware failure such as router failure or switch failure. A h d it should be replaced with a new one.

Are failure may result in data loss and A user can perform network maintenance tasks at regular intervals of time to ensure continuous functioning of a network. This helps in detecting the loopholes in the network and preventing a problem.

We have outlined the possible issues related to network performance till now. To do any task, there should be a general or standardized procedure follow. Similarly, tackling or trouble a problem requires certain basic steps to be followed. Let us discuss these steps in the following section.

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