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CCNA Exploration 2 Chapter 6: VLSM and CIDR

Introduces VLSM and CIDR notation RFC 1519
Introduces Network Address Translator (NAT) in 1994 RFC 1631
RFC for private addressing RFC 1918
Original specification for IPv4 RFC 791
Range for class A addresses to
Range for class B addresses to
Range for class C addresses to
Range for multicast addresses to
Range for experimental addresses to
Protocols that use designated multicast addresses RIPv2, EIGRP, AND OSPF
Classful subnet mask for Class A networks
Number of hosts that Class A can support 16 million host addressses
What happened when companies received Class A addresses? There was a tremendous waste of address space
How many host addresses can a Class B network have? 65534 host addresses
How many host addresses can a Class C network have? 254 host addresses
What is the problem with Class C networks? There are too many networks with too little hosts each one
How can a subnet mask of a network address can be determined using classful IP addresses? It can be determined by the value of the first three bits of the address
Another method to determine and apply a subnet mask for a classful IP address The router applies its ingress interface mask for subnetted routes
What does the router do if it does not have any subnet that belongs to an IP address? It applies the classful mask for the corresponding type of network
What does IETF mean? Internet Engineering Task Force
What was a fundamental cause of the eventual exhaustion of 32-bit IPv4 address space? The lack of a class fit to serve a mid-sized organization that needed thousands of IP addresses but not 65000
What does the use of CIDR allow with respecto to IPv4 addresses? More efficient use of IPv4 address space and refix aggregation (reduction of routing tables)
What characteristic do prefixes have when using CIDR? They can have any length
Allocation of IP addresses with CIDR is based on: Individual needs rather than by class
Another name for route summarization Prefix aggregation
This helps to reduce the size of the Internet routing tables The ability for routes to be summarized
What is a supernet route? A route that summarizes multiple network addresses with a mask less than the classful mask
Why do the propagation of VLSM and supernet routes require the use of classless routing protocols? The subnet mask can no longer be determined by the value of the first octet
How does a router know which subnet mask to apply with classless routing? The subnet mask is included with the network address
When are classless routing protocols needed? When the mask cannot be assumed or determined by the value of the first octet
What type of routes cannot be send by classful routing protocols? Supernet routes
What happens if a supernet route is present in a routing table and a classful protocol is being used? The protocol will not include that route in its updates
For practical uses, what is in fact VLSM? It is subnetting a subnet
If the subnet is subnetted into /24 subnets, to which network does the address belong to? The more specific subnet
An advantage of using VLSM and classless routing More flexibility to create additional network addresses and use a mask that fits your needs
Another name for route summarization Route aggregation
What is route summarization? The process of advertising a contiguous set of addresses as a single address with a shorter subnet mask
Synonim with supernetting CIDR
Some advantages of using CIDR Ignores the limitation of classful boundaries, allows summarization with masks that are less than that of the default mask, helps reduce the number of entries in local routing tables, helps reduce bandwidth
A packet with an address of is sent to a router that has a network and a summary route, to which route is the packet forwarded? To the more specific match which is the network
What is the summary route for networks,,, and
Created by: 100002135751056
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