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Little about Organizational Units

January 26, 2011

An Overview of Organizational Units (OUs) An organizational unit (OU) is a container that is used to logically organize and group Active Directory objects within domains. OUs are not part of the DNS namespace. They are used to organize Active Directory objects into logical administrative groups. OUs therefore serve as containers in which you can [...]

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Special Purpose Network Addresses Every System admin need to know

January 25, 2011

Different types of Classes of Network Class A Addresses Class A address must be between 0 and 127 network.node.node.node Class B Addresses Class B address must be between 128 and 191 network.network.node.node Class C Addresses Class C address must be between 192 and 223 network.network.network.node Network Addresses: Special Purpose Some IP addresses are reserved for special purposes, [...]

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Cisco Layer 2 Switch Functions

January 25, 2011

Layer 2 switch is A network device that forwards traffic based on MAC layer (Ethernet or Token Ring) addresses. Bridging technology has been around since the 1980s (and maybe even earlier). Bridging involves segmentation of local-area networks (LANs) at the Layer 2 level. A multiport bridge typically learns about the Media Access Control (MAC) addresses [...]

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Setting Port Security on a Cisco Catalyst Switch

January 25, 2011

If you want to ensure that only a certain device—for example, a server—is plugged into a particular switch port, you can configure the MAC address of the server as a static entry associated with the switch port. Configure port security Configuring the Port Security feature is relatively easy. In its simplest form, port security requires [...]

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NetBEUI

January 24, 2011

NetBIOS, NetBEUI, and SMB are Microsoft Protocols used to support Microsoft Networking. The NetBIOS stack includes SMB, NetBIOS, and NetBEUI which are described in the table below. The following are parts of the Microsoft networking stack: Name Network Layer Description Redirector Application Directs requests for network resources to the appropriate server and makes network resources [...]

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User Datagram Protocol (UDP)

January 24, 2011

User Datagram Protocol (UDP) supports the network at the transport layer. User Datagram Protocol (UDP) is an unreliable connection-less protocol and is defined by RFC 768 and 1122. It is a datagram service. There is no guarantee that the data will reach its destination. UDP is meant to provide serivce with very little transmission overhead. [...]

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Address Resolution Protocol

January 24, 2011

ARP and RARP Address Translation Address Resolution Protocol (ARP) provides a completely different function to the network than Reverse Address Resolution Protocol (RARP). ARP is used to resolve the ethernet address of a NIC from an IP address in order to construct an ethernet packet around an IP data packet. This must happen in order [...]

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Again Domain Name Service (DNS)

January 24, 2011

Host Names Domain Name Service (DNS) is the service used to convert human readable names of hosts to IP addresses. Host names are not case sensitive and can contain alphabetic or numeric letters or the hyphen. Avoid the underscore. A fully qualified domain name (FQDN) consists of the host name plus domain name as in [...]

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Virtual Private Networking (VPN)

January 24, 2011

The most confusing part of VPN is that many acronyms show up. This is partly because VPN requires data encryption to be “private” and there are many encryption techniques and terms. Also there are many complicated security issues relating to VPN concerning encryption and user authentication. This section will first explain the concept and methodology [...]

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Little About Dynamic Routing

January 24, 2011

Dynamic routing performs the same function as static routing except it is more robust. Static routing allows routing tables in specific routers to be set up in a static manner so network routes for packets are set. If a router on the route goes down the destination may become unreachable. Dynamic routing allows routing tables [...]

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Internet Group Management Protocol (IGMP)

January 24, 2011

Internet Group Management Protocol (IGMP) is the protocol used to support multicasting. To use multicasting, a process on a host must be able to join and leave a group. A process is a user program that is using the network. Group access is identified by the group address and the interface (NIC). A host must [...]

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Little about BOOTP Protocol

January 24, 2011

BOOTP (Boot Protocol) may be used to boot remote computers over a network. BOOTP messages are encapsulated inside UDP messages and therefore its requests and replies are forwarded by routers. BOOTP is defined by RFCs 951 and 1542. The drawing below illustrates the data encapsulation: The diskless system reads its unique hardware address from its [...]

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Little about DHCP

January 24, 2011

Dynamic Host Configuration Protocol (DHCP) This protocol is used to assign IP addresses to hosts or workstations on the network. Usually a DHCP server on the network performs this function. Basically it “leases” out address for specific times to the various hosts. If a host does not use a given address for some period of [...]

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Windows Server 2003 DNS Troubleshooting

January 22, 2011

1) Start Troubleshooting with Ping Can you ping the target machine? a) By IP address. Ping 10.1.0.100 b) By Hostname. Ping BigServer c) By fully qualified domain name. Ping BigServer.guybay.com Examine the replies for clues, for example is the reply BigServer or BigServer.domain.com. Depending on the results from Ping, check the Default Gateway and Subnet [...]

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Little about DNS Queries in Windows Server 2003

January 21, 2011

There are two sides to DNS.  Firstly, registration which adds resource records such as Host (A) into the DNS database.  Secondly there are queries where clients seek those resource records, for example where is BigServer?  Back comes the reply from DNS: BigServer IP = 10.10.55.21. Authoritative DNS Servers The goal of a DNS query is [...]

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