CompTIA® Network+ : Installing And Configuring Routers And Switches
2. Network Installation and Configuration
2.1 Given a scenario, install and configure routers and switches.
The most common configuration problems arise out of switching loops, bad cables, wrong switch/router port configuration, LAN segmentation, wrong IP subnetting, etc. In addition to the physical connections, it is important to configure your network properly. Protocols such as NAT, PAT, VLAN, PoE , QoS are widely used in configuring a network. Hence. it is important to know the types of problems that might occur due to misconfigurations and QoS will give you options within your net work
Some of these protocols have been explained in the following sections:
NAT - Network Address Translation : NAT is very widely used in computer networking. The NAT router has the job of translating the inside network IP addresses to the outside global IP address network (the Internet) enabling inside devices to talk to outside devices and vice-versa, but inside devices can only use addressing consistent with the local network addressing scheme. Similarly, outside devices cannot use local addressing. Thus, both inside and outside devices can be referred to with local or global address versions.
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Address Classification - Initially, it would be a little confusing to understand the terminology like Inside, Outside, Local, and Global. The figure attempts to clear the concepts associated with NAT terminology.
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Inside Global : An inside address seen from the outside. This is a global, publicly-routable IP address used to represent an inside device to the outside world. In a NAT configuration, inside global addresses are those "real" IP addresses assigned to an organization for use by the NAT router.
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Inside Local - An address of a device on the local network, expressed using its normal local device representation. So for example, if we had a client on a network using the 10.0.0.0 private address block, and assigned it address 10.0.0.207, this would be its inside local address.
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Outside Global : An address of an external (public Internet) device as it is referred to on the global Internet. This is basically a regular, publicly-registered address of a device on the Internet. In the example above, 204.51.16.12 is an outside global address of a public server.
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Outside Local : An address of an external device as it is referred to by devices on the local network.
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NAT Pool : A pool of IP addresses to be used as inside global or outside local addresses in translations.
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