3C Flashcards
As discussed earlier, routing involves two basic activities: determination of optimal routing paths (____ ____) and the transport of packets through an internetwork (___ ___).
Path Determination
Packet Switching
Routers use routing tables to determine the best path. Routers populate their routing tables by learning paths to network destinations. The paths can be learned from ____ routes, ____ routes or ____ routes.
static, default or dynamic
Routers chose the path with the lowest ____ ____ (AD) when they know about multiple paths to the same destination from more than one routing source.
Administrative Distance (AD)
Static routes are manually configured by the system administrator as the ____ path to the destination.
only
Static routes are useful for controlling what?
They are useful for controlling security and reducing traffic.
Static routes are basically nothing more than ____ ____ entries established by the network administrator prior to the beginning of routing.
router table
____ ____ entries do not change unless the network administrator alters them.
Static route
Static routes are simple to configure and work well in environments where network traffic is relatively predictable and where network design is relatively simple. However, because static routing systems cannot react to network changes, they generally are considered ____ for today’s large, diverse networks.
unsuitable
Routers know about networks that are directly connected to them if their _____ are functional.
interfaces
When configuring static routes, look for paths that are not directly connected to the router that you want to be part of a path from source to destination. These routes are added to the routing table as ____ ____ reachable.
network destinations
A ___ ____ is a special static route manually defined by the system administrator as the path to take when no route to the destination is known.
default route
A default route, often called the ____ ____ ____ _____,
is a route to which all non-routable packets are sent.
gateway of last resort
___-____ is defined as a network that is not listed in a router’s routing table.
Non-routable
A ____ ____ is a Network Layer protocol that exchanges information packets with other internetwork routers to build and maintain a routing table.
routing protocol
Most of the dominant routing algorithms used today are dynamic routing algorithms such as…?
such as RIP, IGRP, OSPF, EIGRP, and BGP.
What metrics are involved in routing algorithms?
- Path Length
- Reliability
- Delay
- Bandwidth
- Load
- Communication cost
___ ____ is the most common routing metric used in routing algorithms.
Path length
The following describes which routing metric?
Some routing protocols allow network administrators to assign arbitrary costs to each network link. In this case, ___ ____ is the sum of the costs associated with each link traversed. Other routing protocols define hop count as 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.
path length
The following describes which routing metric?
In the context of routing algorithms, refers to the dependability (usually described in terms of the bit-error rate) of each network link. Some network links might go down more often than others. After a network fails, certain network links might be repaired more easily or more quickly than other links. Any reliability factors can be considered in the assignment of a reliability rating. These are arbitrary numeric values usually assigned to network links by network administrators
Reliability
The following describes which routing metric?
refers to the length of time required to move a packet from source to destination through the internetwork. ____ depends on many factors, including the bandwidth of intermediate network links, the port queues (information waiting to be processed) at each router along the way, network congestion on all intermediate network links, and the physical distance to be traveled. Because ____ is a conglomeration of several important variables, it is a common and useful metric.
Delay
The following describes which routing metric?
refers to the available traffic capacity of a link. All other things being equal, a 10Mbps Ethernet link would be preferable to a 64kbps leased line. Although ____ is a rating of the maximum attainable throughput on a link, routes through links with greater ____ do not necessarily provide better routes than routes through slower links. For example, if a faster link is busier, the actual time required to send a packet to the destination could be greater.
Bandwidth
The following describes which routing metric?
refers to the degree to which a network resource, such as a router, is busy. _____ can be calculated in a variety of ways, including CPU utilization and packets processed per second. Monitoring these parameters on a continual basis can be resource intensive.
Load
The following describes which routing metric?
Is another important metric especially because some organizations may not care about performance as much as they care about operating expenses. Even though line delay may be longer, they will send packets over their own lines rather than through the public lines that cost money for usage time. This metric, when used, is set by the Network Administrator.
Communication cost
Algorithms can be classified in several ways; however, we will focus on the two primary types of ____ ____ and ____ ____ algorithms
Distance Vector and Link State algorithms
____ ____ initialize and maintain routing tables, which contain
route information that can vary depending on the routing algorithm used.
Routing Algorithms
____ ____ algorithms use an approach that determines the direction (vector) and distance to any link in the internetwork.
Distance Vector
The network topology changes and at regular intervals. ____ ____ algorithms call for each router to send its entire routing table, but only to its neighbors by way of limited broadcasts.
Distance Vector algorithms
The routing updates do not include subnet masks for the advertised networks. This means all routers in the network must use the same subnet mask. This is known as ____ routing.
classful routing
When a router receives a routing update that includes changes to an entry, it updates its routing table to reflect the new route. After updating its routing table, the router immediately begins transmitting routing updates to inform its neighbor routers of the change. These updates are sent independently of any regularly scheduled updates. This form of routing update is often called “___ ___ ___” since the routers don’t know where the information initially came from and must assume the information is correct
routing by rumor
What are the advantages of distance vector algorithms?
- Simple to understand and configure.
- Do not require much from the router’s processor to maintain the routing table.
- Less expensive to implement and support.
What are the disadvantages of distance vector algorithms?
- Limited by hop count thereby making them unsuitable for large networks
- Variable length subnet masking not supported in RIPv1.
- 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
Link State algorithms are also known as what name?
Shortest path first algorithms
____ _____ algorithms build 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 is the best path available.
Link State algorithms
Link state algorithms use ____ ____ state advertisements to notify other routers in the routing area about the status of their connected links.
multicast link state advertisements
The following is describing which of the algorithms?
When routers receive the message, they copy the information for their own use and immediately resend the message through their other interfaces. This allows for very fast convergence of new information.
Link State algorithms
Benefits provided by ___ ___ algorithms are support for variable length subnet masks (VLSM) and each router sending information describing the state of its own links.
Link State algorithms
Basically, link state algorithms send small updates everywhere, while distance vector algorithms send larger updates but only to their ___ ____.
neighboring routers
Because they converge more quickly, link state algorithms are less prone to ____ ____ than distance vector algorithms.
routing loops
On the other hand, link state algorithms require more ___ _____ and
______ than distance vector algorithms. Link state algorithms, therefore, can be more expensive to implement and support.
CPU power and memory
Interior routing protocols are used to exchange information between routers within ____ ____.
Autonomous Systems
We will look at the most common interior gateway routing protocols which are based on either a distance vector algorithm (___), a link state algorithm (OSPF), or a balanced hybrid of the two algorithm types. (EIGRP)
(RIP)
Routing Information Protocol or RIP, as it is more commonly called, utilizes a ____ ____ algorithm.
Distance Vector algorithm