A collection of individual networks, connected by intermediate networking devices that function as a single large network.
What are the four common challenges to internetworks?
Connectivity, Reliable Service, Network Management, and Flexibility
A group of devices connected to the same physical media so that when two devices try to access the media at the same time, the two signals will collide with each 1-3
other and destroy the data stream.
A portion of the network, limited by its router connection to a specific group of host computers in a common LAN segment.
What devices are used to segment networks into collision domains?
Switches and Bridges
What devices are used to subdivide a network into broadcast domains?
A formal set of rules and conventions that governs how computers and other network entities exchange information over a network medium.
What type of address is commonly referred to as a virtual or logical address?
Network or IP address
How many network-layer addresses do routers require?
Routers and other internetworking devices require one network-layer address per physical network connection for each network-layer protocol supported.
What's the difference between routing and routed protocols?
Routing protocols build routing tables whereas routed protocols encapsulate data to be sent over the network.
Protocols within a protocol suite that are responsible for providing the logical addressing that routers use to determine where to send the data packet on its way to the destination network.
What are some examples of routed protocols?
IP, ARP, Hello protocol, and ICMP.
What are some examples of routing protocols?
RIP, IGRP, OSPF, Enhanced IGRP, and BGP.
The primary routed network-layer protocol and is considered the heart of the Internet protocols.
What are the two primary responsibilities of IP?
Providing connectionless, best-effort delivery of packets through an internetwork based on logically assigned addresses; and providing fragmentation and reassembly of packets to support data links with different maximum-transmission unit (MTU) sizes.
Which protocol is used to map IP network addresses to Media Access Control addresses?
Address Resolution Protocol (ARP)
A network layer protocol that is used to send packets, which act as keep-alives, between routers.
A network-layer internet protocol that provides message packets to report errors and other information regarding IP packet processing back to the source.
Internet Control Message Protocol (ICMP)
What kind of useful messages does ICMP generate?
Destination Unreachable, Time Exceeded, Router Advertisement, Router Solicitation, Echo Request and Echo Reply (PING).
Network-layer protocols that are responsible for path determination and packet (traffic) switching.
A collection of networks under a common administration that share a common routing strategy.
List 4 examples of Interior Gateway Protocols.
Routing Information Protocol (RIP), Interior Gateway Routing Protocol (IGRP), Open Shortest Path First (OSPF), and Enhanced IGRP.
What is an example of an Exterior Gateway Protocol?
Border Gateway Protocol (BGP)
An IP address on a layer 3 network device that serves as an access point to or from a network.
The act of moving information across a packet switching internetwork from a source to a destination.
What layer does bridging/switching occur at?
What layer does routing occur at?
What are the two major functions of routing?
Path determination and packet switching.
What must a router have to perform its functions on the network?
• A destination address from the layer 3 packet header
• Other routing sources it can learn from
• A list of possible routes
• The ability to select the best route
• A process to maintain and verify its routing information
What does the router use to best decide how to forward packets across the internetwork?
A standard of measurement, such as path length, that is used by routing algorithms to determine the optimal path to a destination.
A mathematical formula used to calculate the cost in network resources associated with a specific pathway to a destination network; used to initialize and maintain routing tables.
Electronic tables or databases containing updated information about available networks and best paths to known networks.
A message that generally consists of all or a portion of a routing table that is sent to its neighbor routers.
Broadcast (routing update message)
An example of a message sent between routers throughout the network to inform other routers of the state of the sender's links.
Multicast (link-state advertisement)
What are three external components that most routers usually have?
Console port, auxiliary port, and network interfaces.
Port that allows you to configure the router locally by providing direct access to the router using a computer running terminal emulation software.
Port that allows you to configure the router remotely using a modem
What are the internal components of a router?
ROM, flash memory, NVRAM, and RAM
The internal component of a router where the diagnostic and boot up routines are stored.
The internal component of a router which holds the Internetwork Operating Systems (IOS)
The internal component of a router that is used to store the startup-configuration file.
The internal component of a router that is a working memory for the router; contains the running-configuration file, a copy of the IOS, the routing tables, and any associated data required by the routing process.
Manually defined by the system administrator as the only path to the destination; they are useful for controlling security and reducing traffic.
What are the advantages of static routes?
They're simple to configure and work well in environments where network traffic is relatively predictable and where network design is relatively simple.
What's the disadvantage of static routes?
Because static routing systems cannot react to network changes, they are generally considered unsuitable for today's large, diverse networks.
A special static route manually defined by the system adminstrator as the path to take when no route to the destination is known; also known as the gateway of last resort, a router to which all non-routable packets are sent.
A network layer protocol that exchanges information packets with other internetwork routers in order to build and maintain a routing table.
Dynamically learned route (routing protocol)
The most common routing metric; the sum of the costs associated with each link traversed.
A metric that specifies the number of passes (hops) through internetworking devices, such as routers, that a packet must take from a source to a destination.
In the context of routing algorithims, refers to the dependability (usually described in terms of the bit-error rate) of each network link.
Refers to the length of time required to move a packet from source to destination through the internetwork.
Refers to the available traffic capacity of a link.
Refers to the degree to which a network resource, such as a router, is busy.
Routing metric set by the network adminstrator that is important, especially becuase some organizations may not care about performance as much as they care about operating expenses.
Class of algorithm that sends packets to a destination using the same or single path unless there is a topology change that affects the available route.
Class of algorithm that supports multiple paths to the same destination by load balancing or load sharing; permit traffic multiplexing over multiple lines.
Class of algorithm in which the routers are peers of all others (all routers in the domain use the same subnet masking, sometimes referred to as "Classful" routing.
Class of algorithm whose routing structure is called "Classless" routing and supports Variable Length Subnet Masks (VLSM).
Class of algorithm that works only within a routing domain and used with Interior Gateway Protocols to exchange routing information within an Autonomous System or routing domain.
Class of algorithm used with Exterior Gatway Protocols that exchange routing information within and between Autonomous Systems such as on the Internet.
Class of algorithm that uses an approach that determines the direction (vector) and distance to any link in the internetwork.
Distance vector algorithm
Class of algorithms that call for each router to send all or some portion of its routing table, but only to its neighbors by way of Limited Broadcasts which is the 255.255.255.255 broadcast that routers are designed not to pass.
Distance vector algorithm
What are the advantages of Distance-Vector protocols?
They are simple to understand and configure as well as not requiring much from the router's processor to maintain the routing table. They are also less expensive to implement and support.
What are the disadvantages of Distance-Vector protocols?
They are limited by hop count, thereby making them unsuitable for large networks. Also, they update by broadcast and build their routing tables from their neighbor's routing tables. This means they are routing based on information that cannot be verified as accurate (routing by rumor).
Classification of algorithm also known as the shortest path first algorithm, that builds a complete topological map of the entire area in memory, which allows them to "see" the entire path to the destination network ensuring the path is valid and the best path available.
Link state algorithm
What are the advantages of link-state algorithms?
Because they converge more quickly, liink-state algorithms are less prone to routinng loops than distance-vector algorithms.
What are the disadvantages of link state algorithms?
They require more CPU power and memory than distance-vector algorithms, therefore they can be more expensive to implement and support.
What are the three classes of protocols?
Distance Vector protocols, Link State protocols and Balanced Hybrid protocols
What are two examples of Distance Vector protocols?
Router Information Protocol (RIP) and Interior Gateway Routing Protocol (IGRP).
Which protocol is considered a pure distance vector routing protocol?
Routing Information Protocol (RIP)
Protocol that uses only path length or hop count for its calculations to insert routes into the routing table.
Routing Information Protocol (RIP)
Protocol that is a distance vector routing protocol that is designed to operate within autonomous systems that have a complex topology.
Interior Gateway Routing Protocol (IGRP)
A link-state routing protocol that only sends information which describes the state of its own links to all the routers within the hierarchical area.
Open Shortest Path First (OSPF)
What algorithm do OSPF routers use to calculate the shortest path to each router.
A collection of networks, also called a routing domain, under a common administration that share a common routing strategy and is the largest entity within the hierarchy.
What type of routing occurs when the source and destination are in the same area?
What type of routing occurs when they are in different areas?
Term for routers with multiple interfaces that can participate in multiple areas and maintain separate topological databases for each area.
Area border routers
What is an OSPF backbone responsible for?
An OSPF backbone is responsible for distributing routing information between areas.
When an ospf router is initializing, what protocol does it use to acquire neighbors?
When a router discovers a new neighbor, it records the neighbor's address and interface as an entry where?
The neighborship database
An overall picture of networks in relationship to routers that contains the collection of Link State Advertisements (LSAs) received from all routers in the same areas.
When the link-state databases of two neighboring routers are synchronized, they are said to be what?
Which routers is responsible for generating Link State Advertisements for the entire area so only one router is responsible for sending multicast updates?
Table that compiles the shortest routing pathways from the topological database.
What are the advantages of OSPF?
• Hierarchical routing supports very large networks.
• Shortest Path First algorithm allows for fast convergence.
• Does not suffer from the routing loop issues (unlike distant vector protocols).
• Smaller routing updates and they only occur when there is a topology change (less bandwidth and CPU utilization).
• Hierarchical routing supports very large networks.
What are the disadvantages of OSPF?
• Complex, requires a structured topology (otherwise efficiency will be reduced).
• Requires highly trained staff to understand and configure a large OSPF network due to complex configurations.
• Link State database requires considerable memory due to numerous tables and databases.
• SPF algorithm utilizes more processing power as the size of the topology database increases.
Enhanced Interior Gateway Routing Protocol (EIGRP) is an example of what class of protocol?
Balanced Hybrid Protocol
Protocol that maintains copies of its neighbor’s routing tables and uses these distance vectors to determine the best paths to destination networks, but resembles link-state protocols in the way it uses topology changes only to trigger link state updates by using multicast messages.
What are the three key technologies employed by EIGRP?
Neighbor Discovery/Recovery, Reliable Transport Protocol (RTP), and DUAL Finite-State Machine.
Key technology used by EIGRP routers to dynamically learn about other routers on their directly attached networks in a process achieved by low overhead by periodically sending small Hello protocol packets.
Key technology used by EIGRP that is responsible for guaranteed, ordered delivery of EIGRP packets to all neighbors.
Reliable Transport Protocol (RTP)
Key technology used by EIGRP that embodies the decision process for all route computations by tracking all routes advertised by all neighbors.
The best, least cost path to a destination that is guaranteed not to be part of a loop.
Where is the successor stored?
It is stored in thhe topology table but also copied to the routing table as the best route to a destination.
What is the next best path to the successor available to a destination that is guaranteed not to be part of a routing loop.
Where are feasible successors stored?
Feasible successors are stored in the topology until needed.
EIGRP relies on what fundamental routing concepts for route discovery and maintenance?
Protocol-Dependent Modules, Neighbor tables, Topology tables, and Route states
Routing concept that maintains a separate set of neighbor tables, topology tables and routing tables containing the routing information that applies to a specific protocol such as IP, IPX, IPv6 or AppleTalk.
Protocol-Dependent Modules (PDM)
When a router discovers a new neighbor, it records the neighbors address and interface as an entry where?
The neighbor table
Contains all destinations advertised by neighboring routers.
What are the two states a topology-table entry for a destination can exist in?
Active or passive
What does it mean when a destination is in passive or active state?
A destination is in the passive state when the router is not performing a recomputation or in the active state when the router is performing a recomputation.
In EIGRP, the best paths (successors) to each known network are extracted from the topology table to build what as computed by DUAL?
What radical improvements does EIGRP have over RIP and IGRP?
• Fast convergence when a feasible successor is available.
• Variable Length Subnet Masks are supported - subnet mask information is exchanged in EIGRP updates.
• Smaller routing updates only sent when a topology change occurs.
• Ease of configuration - similar to RIP.
What are the disadvantages of EIGRP?
• Higher memory requirements for its tables (topology, neighbor, and routing).
• Routing Algorithm is complex and can be CPU-intensive during periods of network instability and recalculations.
• EIGRP is Cisco proprietary.
A measure of trustworthiness attached to each source of routing information.
Type of routing protocol used when communications are required between autonomous systems.
Exterior Gateway Protocol (EGP)
What is the predominant EGP (exterior gateway protocol) in use today, the one that runs the internet?
Border Gateway Protocol
What is the primary function of BGP?
The primary function of BGP is to exchange routing information between autonomous systems while guaranteeing loop-free path selection.
What type of routes are designed to work well where network traffic is extremely predictable and network design is relatively simple?
________ routes use algorithms to build and maintain routing tables that adjust to changing network topology.
Protocols such as RIP, IGRP, EIGRP, OSPF and BGP are classified as ______ routes.
Distance Vector algorithms build routing tables by using __________ messages to and from their neighbors only.
broadcast routing updates
A disadvantage of distance vector algorithms is they are limited by _____ ______ making them unsuitable for large networks.
Explain why link-state protocols have a shorter convergence time than distance vector protocols.
Link-state protocols only message link-status updates while distance vector protcols broadcast the entire routing table.
The _______ _______ is responsible for generating link-state advertisements for an entire area so only one router is responsible for sending out multicast messages.
_____ _____ _____ sends small “hello” packets to establish communication with neighboring routers.
What algorithm does EIGRP use for route determination?
DUAL (Diffusing Update Algorithm)
When is an administrative distance used?
Administrative distance is used if there are multiples sources for a routing table entry.
Which protocol path would be used if OSPF and EIGRP both provided a path to the same destination?
How does BGP discover its neighbor routers?
The network administrator must manually define BGP neighbors (during configurations) and initiate a TCP connection-oriented session between the neighbor routers.