Specialized Network Devices

Multilayer Switch – A high performance device can operate at both layers 2 and 3 of the OSI Model

Content Switch – Another specialized device use for load balancing and high performance

Intrusion Detection System – A mechanism use to monitor inbound and outbound network traffic

Intrusion Prevention System – A mechanism use to prevent network attacks and monitor traffic

Load Balancer – A device use to distribute network traffic evenly

Multifunction Network Devices – A device that can perform multiple function in a network

DHCP Server – A device use to automatically distribute IP information

DNS Server – A device use to provide name resolution from hostname to IP addresses

Bandwidth Shaper – A mechanism use to control bandwidth usage on a network (Monitor/Shaping)

Proxy Server – A device that sits between a client computer and the Internet, looking for web page requests the client sends. It is use for performance such as a caching engine

CSU/DSU – Channel Service Unit/Digital Service Unit acts a translator between LAN data format and the WAN data format

Media Converter – Interconnects older technology with new

Firewall – A hardware or software use to protect network from outside attacks

Advance Features of a Switch

POE- Power over Ethernet is a technology that allows electrical power to be transferred over cable

Spanning Tree – STP Protocol is used with bridges and switches it eliminates and avoids loops

Trunking – Use of multiple network cables or ports in parallel to increase link speed

Link Aggregation - A method use to increase throughput

Port Mirroring – A method of monitoring network traffic and to configure a copy of all inbound and outbound traffic to go to a certain port

Port Authentication – Authenticating users on a port-by-port basis (802.1x standards)


Link-state routing protocol is one of the two main classes of routing protocols used in packet switching networks for computer communications, the other major class being the distance-vector routing protocol.
Examples of link-state routing protocols include OSPF and IS-IS.

The link-state protocol is performed by every switching node in the network (i.e. nodes that are prepared to forward packets; in the Internet, these are called routers). The basic concept of link-state routing is that every node constructs a map of the connectivity to the network, in the form of a graph, showing which nodes are connected to which other nodes. Each node then independently calculates the next best logical hop from it to every possible destination in the network. The collection of best next hops will then form the node's routing table.

OSPF is an interior gateway protocol that routes Internet Protocol (IP) packets solely within a single routing domain (autonomous system). It gathers link state information from available routers and constructs a topology map of the network. The topology determines the routing table presented to the Internet Layer which makes routing decisions based solely on the destination IP address found in IP datagrams.

Intermediate system to intermediate system (IS-IS), is a protocol used by network devices (routers) to determine the best way to forward datagrams through a packet-switched network, a process called routing.

The Distance-vector routing protocol is one of the two major classes of routing protocols used in packet-switched networks for computer communications, the other major class being the link-state protocol.

RIP is a distance-vector routing protocol, which employs the hop count as a routing metric. Different versions of RIP includes RIP1 and RIP2

Border Gateway Protocol (BGP) is the core routing protocol of the Internet. It maintains a table of IP networks or 'prefixes' which designate network reach-ability among autonomous systems (AS).


Enhanced Interior Gateway Routing Protocol - (EIGRP) is a Cisco proprietary routing protocol loosely based on their original IGRP. EIGRP is an advanced distance-vector routing protocol, with optimizations to minimize both the routing instability incurred after topology changes, as well as the use of bandwidth and processing power in the router.

  • Interior Gateway Protocols
    • within a single autonomous system
      • single network administration
      • unique routing policy
      • make best use of network resources
  • Exterior Gateway Protocols
    • among different autonomous systems
      • independent administrative entities
      • communication between independent network infrastructures

Convergence is an important notion for a set of routers that engage in dynamic routing. For a set of routers to have converged, they must have collected all available topology information from each other via the implemented routing protocol, the information they gathered must not contradict any other router's topology information in the set, and it must reflect the real state of the network.