Term
| What services does the network layer provide? |
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Definition
| provides services to exchange the individual pieces of data over the network between identified end devices |
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Term
| What are the 4 basic processes used at the network layer? |
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Definition
| Addressing * Encapsulation * Routing * Decapsulation |
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Term
| What is the PDU of the network layer? |
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Definition
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Term
| What information is contained in the layer 3 PDU? |
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Definition
| the header must contain, among other information, the address of the host to which it is being sent. This address is referred to as the destination address. The Layer 3 header also contains the address of the originating host. This address is called the source address. |
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Term
| What is the role of a router? |
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Definition
| to select paths for and direct packets toward their destination |
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Term
| What is it called when a packet passed through an intermediary device? |
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Definition
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Term
| What happens to the transport layer PDU as the packet moves through the network? |
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Definition
| manages the data transport between the processes running on each end host |
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Term
| What does the network layer protocol specify? |
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Definition
| specify the packet structure and processing used to carry the data from one host to another host. |
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Term
| List the 5 Network layer protocols. |
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Definition
Internet Protocol version 4 (IPv4)
Internet Protocol version 6 (IPv6)
Novell Internetwork Packet Exchange (IPX)
AppleTalk
Connectionless Network Service (CLNS/DECNet) |
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Term
| Which protocol will be the focus of this class? |
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Definition
| Internet Protocol (IPv4 and IPv6) |
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Term
| What are the basic characteristics of IPv4? |
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Definition
| 1.Connectionless - No connection is established before sending data packets. 2. Best Effort (unreliable) - No overhead is used to guarantee packet delivery. 3.Media Independent - Operates independently of the medium carrying the data. |
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Term
| Describe what a connectionless service in networking means? |
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Definition
| sending a letter to someone without notifying the recipient in advance |
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Term
| What is the main issue that may occur in a connectionless exchange? |
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Definition
| result in packets arriving at the destination out of sequence. If out-of-order or missing packets create problems for the application using the data, then upper layer services will have to resolve these issues. |
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Term
| What does unreliable mean in networking? |
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Definition
| does not have the capability to manage / recover undelivered/ corrupt packets |
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Term
| Which layer is responsible for adding reliability to packet delivery? |
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Definition
| TCP/IP suite, the Transport layer can choose either TCP or UDP |
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Term
| Describe media independent. |
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Definition
| The Network layer is also not burdened with the characteristics of the media on which packets will be transported. IPv4 and IPv6 operate independently of the media that carry the data at lower layers of the protocol stack. |
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Term
| What layer is responsible for preparing a packet for the media? |
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Definition
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Term
| What is the one characteristic of the network layer that is dependent on the media? |
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Definition
| the maximum size of PDU that each medium can transport. This characteristic is referred to as the Maximum Transmission Unit (MTU). an intermediary device - usually a router - will need to split up a packet when forwarding it from one media to a media with a smaller MTU. This process is called fragmenting the packet or fragmentation. |
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Term
| What portion of the IP packet does a router use to make forwarding decisions? |
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Definition
| only considers the contents of the packet header that encapsulates the segment |
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Term
| What remains untouched as packets travel through the network? |
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Definition
| the data portion of the packet - that is, the encapsulated Transport layer PDU - remains unchanged during the Network layer processes |
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Term
| What are the 6 key fields in an IP packet? |
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Definition
| 1.IP Source Address 2. IP Destination Address 3. Time-to-Live (TTL) 4. Type-of-Service (ToS) 5.Protocol 6.Fragment Offset |
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Term
| What happens to a packet if the TTL field reaches 0? |
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Definition
| the router discards or drops the packet and it is removed from the network data flow. Prevents a router loop. |
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Term
| What is the checksum field used for? |
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Definition
| error checking the packet header. |
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Term
| What are three methods of determining how to divide your network? |
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Definition
| Geographic location, Purpose, Ownership |
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Term
| Why would you group users geographically? |
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Definition
| can improve network management and operation |
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Term
| Why would you group users by task? |
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Definition
| typically use common software, common tools, and have common traffic patterns. We can often reduce the traffic required by the use of specific software and tools by placing the resources to support them in the network with the users |
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Term
| Why would you group networks by ownership? |
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Definition
| provides a boundary for security enforcement and management of each network. |
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Term
| What are the 3 main issues as networks grow larger? |
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Definition
| Performance degradation, Security issues, Address Management |
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Term
| What is a network broadcast? |
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Definition
| a message sent from one host to all other hosts on the network, a necessary and useful tool used by protocols to enable data communication on networks |
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Term
| What is broadcast domain? |
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Definition
| Broadcasts are contained within a network |
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Term
| Is it good or bad to increase the number of broadcast domains in your network? |
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Definition
| GOOD - ensures that network and host performances are not degraded to unacceptable levels |
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Term
| What is the major advantage of dividing networks by ownership? |
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Definition
| access to and from resources outside each network can be prohibited, allowed, or monitored. |
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Term
| What efficiency does dividing large networks into separate networks provide to the hosts? |
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Definition
| reduces the unnecessary overhead of all hosts needing to know all addresses |
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Term
| What is the device called that hosts send information to that must travel outside their network? |
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Definition
| This intermediary device is called a gateway. The gateway is a router on a network that serves as an exit from that network. |
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Term
| What is hierarchical addressing? |
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Definition
| uniquely identifies each host. It also has levels that assist in forwarding packets across internetworks, which enables a network to be divided based on those levels. |
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Term
| What is the example presented that describes hierarchical addressing in our daily lives? |
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Definition
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Term
| How many bits are in an IPv4 address? |
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Definition
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Term
| How is the ip address divided? |
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Definition
| divided in four groups of eight bits (octets). Each octet is converted to its decimal value and the complete address written as the four decimal values separated by a dot (period). For example - 192.168.18.57 |
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Term
| What portion of the IP address does a router use? |
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Definition
| and the last octet, identifies the host. Routers only need to know how to reach each network. – the last octet |
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Term
| What is the actual address used for a default gateway? |
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Definition
| To communicate with a device on another network, a host uses the address of this gateway, or default gateway, to forward a packet outside the local network. 198.168.2.0 |
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Term
| What is the route that the router forwards a packet to called? |
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Definition
| the next-hop address or router |
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Term
| What decisions do routers make as a packet enters an interface? |
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Definition
| forwarding decisions are based on the information in the IP packet header |
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Term
| How is the default gateway configured on a host running windows? |
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Definition
| The default gateway is configured on a host. On a Windows computer, the Internet Protocol (TCP/IP) Properties tools are used to enter the default gateway IPv4 address |
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Term
| What portion of the IP address must be the same for the host and gateway? |
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Definition
| Both the host IPv4 address and the gateway address must have the same network (and subnet, if used) portion of their respective addresses. |
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Term
| What command is issued at the command prompt of windows to see the default gateway setting? |
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Definition
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Term
| What is it called when a router makes forwarding decisions? |
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Definition
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Term
| What is the map called that a router uses to make forwarding decisions (Hint: look at the figure)? |
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Definition
| uses a route to map the destination network address to the next hop and then forwards the packet to this next-hop address. |
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Term
| What does a routing table contain? |
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Definition
| Tracks the routes to particular network destinations. |
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Term
| What are the 3 main features of routes in a routing table? |
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Definition
| Destination network, Next-hop, Metric |
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Term
| What happens if the packet does not have an address contained in the routing table? |
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Definition
| the packet will be dropped (that is, not forwarded) The router may also use a default route to forward the packet |
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Term
| What is a default route used for? |
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Definition
| used when the destination network is not represented by any other route in the routing table. |
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Term
| What is the command to view the routing table for a host? |
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Definition
| netstat -r, route, or route PRINT commands. |
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Term
| What is the destination network IP address and subnet mask for the default network interface? |
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Definition
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Term
| What three commands are listed that allow you to change the routing table? |
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Definition
| route ADD , route DELETE , route CHANGE |
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Term
| What does the address in the routing table represent? |
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Definition
| a range of host addresses and sometimes a range of network and host addresses. |
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Term
| If more than one route exists in the routing table for an address, which one will be selected? |
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Definition
| the router will select the most specific route |
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Term
| When is the default route used? |
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Definition
| used to forward packets for which there is no entry in the routing table for the destination network |
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Term
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Definition
| the address of the device that will process the packet next |
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Term
| Why does a directly connected device not have a next-hop? |
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Definition
| because there is no intermediate Layer 3 device between the router and that network - The router can forward packets directly out the interface onto that network to the destination host. |
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Term
| What are the three decisions a router can make about a packet? |
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Definition
| Forward it to the next-hop router, Forward it to the destination host, Drop it |
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Term
| Which layer does a router process packets at? |
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Definition
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Term
| What layer is the packet encapsulated at before it leaves the router? |
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Definition
| Data Link layer – Layer 2 |
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Term
| What is another name for a default gateway? |
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Definition
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Term
| Why would a packet take a different route than another packet that is part of the same data stream? |
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Definition
| Routers along the way may learn new routes while the communication is taking place and forward later packets to different next-hops. |
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Term
| Why are default routes so important to routers? |
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Definition
| because the gateway router is not likely to have a route to every possible network on the Internet. If the packet is forwarded using a default route, it should eventually arrive at a router that has a specific route to the destination network. This router may be the router to which this network is attached. In this case, this router will forward the packet over the local network to the destination host. |
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Term
| What happens if a router has no route for the packet and does not have a default route? |
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Definition
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Term
| Why doesn’t IP have error notification? |
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Definition
| Such a function would detract from the protocol's efficiency and low overhead. |
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Term
| What does a router need to forward a packet? |
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Definition
| have a route to forward the packet |
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Term
| What happens if routing table are not up to date? |
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Definition
| Out-of-date routing information means that packets may not be forwarded to the most appropriate next-hop, causing delays or packet loss |
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Term
| What are two ways a router can learn about routes? |
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Definition
| can be manually configured on the router or learned dynamically from other routers in the same internetwork |
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Term
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Definition
| Routes to remote networks with the associated next hops can be manually configured on the router - default route can also be statically configured |
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Term
| What must be done if the internetwork changes? |
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Definition
| internetwork structure changes or if new networks become available, these changes have to be manually updated on every router |
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Term
| What is the definition of a dynamic routing protocol? |
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Definition
| Routing protocols are the set of rules by which routers dynamically share their routing information. As routers become aware of changes to the networks for which they act as the gateway, or changes to links between routers, this information is passed on to other routers |
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Term
| What happens when a router receives information about changes in routes? |
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Definition
| it updates its own routing table and, in turn, passes the information to other routers. |
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Term
| What are 3 common routing protocols? |
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Definition
| Routing Information Protocol (RIP), Enhanced Interior Gateway Routing, Protocol (EIGRP), Open Shortest Path First (OSPF) |
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Term
| What are the 2 costs listed with using a dynamic protocol? |
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Definition
| First, the exchange of route information adds overhead that consumes network bandwidth. Second, the route information that a router receives is processed extensively by protocols such as EIGRP and OSPF to make routing table entries. |
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Term
| What advantages are listed for static routing? |
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Definition
| Static routing does not produce any network overhead and places entries directly into the routing table; no processing is required by the router. The cost for static routing is administrative - the manual configuration and maintenance of the routing table to ensure efficient and effective routing. |
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