Network+ (N10-008) Cram Notes

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2. Network Installation and Configuration

2.3 Explain the purpose and properties of DHCP.

  • Static Addressing: You can request a static IP address it is one IP address for only one customer and is constant. These are more reliable for VOIP, for hosting gaming websites and to use VPN. Another advantage is that because you IP is static that is it will not be assigned to any other you need not worry of your IP getting blacklisted because of some only else sending SPAM.

  • Dynamic addressing: When DHCP client boots, it sends out a DHCP discover message. All DHCP servers answer with an offer message that includes an address which is available to the client. client machine typically repeats the discover message several times to make sure it hears from all the servers, then eventually chooses one server The currently active DHCP server is configured by hand to handle and reserve IP addresses and the IP configuration information that goes with them. Addresses are made available in an order that permits a client to have the best chance of getting back the same address it was using most recently. IP configuration information gets automatically configured for your client machine by the DHCP server.

  • DHCP reservation: If you set a DHCP Reservation the computer you set will get the same IP each time but it will be given out by the DHCP server. DHCP reservation is a permanent IP address assignment. It is a specific IP address within a DHCP scope that is permanently reserved for leased use to a specific DHCP client.

  • DHCP scope: DHCP scope is the consecutive range of possible IP addresses that the DHCP server can lease to clients on a subnet. These are the primary way for the DHCP server to manage distribution and assignment of IP addresses. These define a single physical subnet on network to which DHCP services are offered.

  • DHCP lease: DHCP clients get a lease for IP address from server. DHCP server must renew the lease before it expires for the client or client should obtain a new lease. DHCP server database provides an extension of one day after expiration that is database will retain lease information in database for one after expiration this grace period is provided to handle time zone difference , internal clock differences.

2.4 Given a scenario, troubleshoot common wireless problems.

  • Interference: Wireless networks use radio signals to transmit signals and are subjected to interference from many factors. Any electrical device around wireless access point that produce radio waves can cause interference.

  • Signal strength: User always want to connect to the network with highest signal strength. If a user is getting low signal strength either user or WAP can be moved to improve signal strength. Also changing the antenna type can improve signal strength.

  • Configuration: User should not be required to do many configuration changes. Broadcasting SSID will allow user to detect the network and make connection. Any security protocol information and password required by end user should also be communicated in order to make connection.

  • Encryption type: To ensure maximum security for wireless networks highest encryption protocols must be used that are supported by both WAP and clients. Both WAP and clients must be configured with same encryption type.

2.5 Given a scenario, troubleshoot common router and switch problems.

  • Bad Cables/ improper cables: For a network to work efficiently proper cable should be used. Use of improper cable can cause connection issues and low performance.

  • Port configuration: Port configurations should be done according to design of network , topology being used and main use of the port. Some port configuration include opening and shutting the port, setting duplex, encryption type, protocols etc..

  • VLAN assignment: It can be used to create virtual networks. This assignment should be done properly to include clients in specific subnet. If assignment is not done correctly it can lead to in efficiency, connectivity issues and some time security issues too.

  • Mismatched MTU/MTU black hole: Maximum Transmission Unit is Maximum Transmission Unit it is largest size packet that will be expected by a network. It interfaces used to connect devices are not with same MTU then packet drop can occur and client will not be able to receive data properly.

  • Power failure: power failure can can stop routers and switches to stop working and can effect working of the network so UPS should be used to provide continuous power.

  • Bad/missing routes: If some information in routing tables is incorrect or is missing it can effect routers ability to make proper decision. If a routing protocol is properly configured it will automatically provide all routing information.

  • Duplicate IP address: Because of some misconfiguration duplicate address can be placed in the network. This issue can be detected by operating system can will be reported easily.

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