Post on 13-Dec-2015
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 1
Cisco Systems CCNA Version 3 Semester 1
Module 10
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 2
Overview
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 3
Module 10: Routing Fundamentals and Subnets10.1 Routed Protocol
10.1.1 Routable and routed protocols 10.1.2 IP as a routed protocol 10.1.3 Packet propagation and switching within a router 10.1.4 Internet Protocol (IP) 10.1.5 Anatomy of an IP packet
10.2 IP Routing Protocols10.2.1 Routing overview 10.2.2 Routing versus switching 10.2.3 Routed versus routing 10.2.4 Path determination 10.2.5 Routing tables 10.2.6 Routing algorithms and metrics 10.2.7 IGP and EGP 10.2.8 Link state and distance vector 10.2.9 Routing protocols
10.3 The Mechanics of Subnetting10.3.1 Classes of network IP addresses 10.3.2 Introduction to and reason for subnetting 10.3.3 Establishing the subnet mask address 10.3.4 Applying the subnet mask 10.3.5 Subnetting Class A and B networks 10.3.6 Calculating the resident subnetwork through ANDing
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 4
10.1.1 Routable and routed protocols
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 5
• The network address is obtained by ANDing the address with the network mask.
• The reason that a network mask is used is to allow groups of sequential IP addresses to be treated as a single unit.
10.1.1 Routable and routed protocols
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 6
IP is a connectionless, unreliable, best-effort delivery
protocol.
IP determines the most efficient route for data, based on the routing protocol.
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 7
10.1.2 IP as a routed protocol
MACd MACs IPs IPd Ps Pd
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 8
10.1.3 Packet propagation and switching within a router
MACd MACs
IPs IPd
Ps Pd
• Reliable• connection-
oriented
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 9
Frame Header
MAC destinatio
n
IP Header
IP sourceMAC
source IP destinatio
n
Frame Trailer(FCS/CRC)
Segment Header
Port source
Port destinatio
n
MACd MACs IPs IPd Ps Pd
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 10
One Complete Maximum Frame
MACd MACs IPs IPd Ps Pd
Frame Header
MAC addresses
IP Header
IP addresses
Data…
…Data…
…Data…
FCS
…Data
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 11
10.1.3 Packet propagation and switching within a router
Each time a packet is switched from one router interface to another the packet is de-encapsulated then encapsulated once
again.
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 12
10.1.3 Packet propagation and switching within a router
MACd MACs
IPs IPdPs Pd
The Empty Frame is Thrown Away…
• The MAC address is changed each time the packet passes through a router.
• The Router interface is part of the attached LAN. Like a host, the router uses the MAC address to exchange topological (physical) information.
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 13
10.1.3 Packet propagation and switching within a router
Discarded MAC addresses
Eventually these discarded Mac addresses will pile up and should be
returned to the Manufacturer for recycling.
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 14
10.1.3 Packet propagation and switching within a router
MACd MACs IPs IPd
…and a new one is created with the Router’s Mac address.
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 15
10.1.3 Packet propagation and switching within a router
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 16
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 17
10.1.3 Packet propagation and switching within a router
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 18
10.1.3 Packet propagation and switching within a router
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 19
10.1.3 Packet propagation and switching within a router
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 20
10.1.3 Packet propagation and switching within a router
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 21
10.1.3 Packet propagation and switching within a router
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 22
10.1.3 Packet propagation and switching within a router
Routers determine the subnet network address based upon a given IP address and subnet mask by binary ANDing the two together.
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 23
10.1.3 Packet propagation and switching within a router
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 24
10.1.3 Packet propagation and switching within a router
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 25
MACd MACs
IPs IPd
Ps Pd
10.1.3 Packet propagation and switching within a router
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 26
10.1.3 Packet propagation and switching within a router
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 27
10.1.4 Internet Protocol (IP)
IP is a connectionless service. The route that the packet takes is determined by the
routers.
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 28
WAN Services
Dedicated Physical - PPP
ISDN – Private Physical Switched
VPN - Public Packet Switchedinternet
privateFrame Relay - Private Packet
Switched
Point of Demarcatio
n
The Telephone Company owns all the infrastructure
Many ways to do this.
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 29
10.1.5 Anatomy of an IP packet
MACd MACs IPs IPd Ps Pd
IP Stuff
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 30
• Version – Indicates the version of IP currently used; four bits. If the version field is different than the IP version of the receiving device, that device will reject the packets.
• *IP header length (HLEN) – Indicates the datagram header length in 32-bit words. This is the total length of all header information, accounting for the two variable-length header fields.
• Type-of-service (TOS) – Specifies the level of importance that has been assigned by a particular upper-layer protocol, eight bits.
• Total length – Specifies the length of the entire packet in bytes, including data and header, 16 bits. To get the length of the data payload subtract the HLEN from the total length.
• Identification – Contains an integer that identifies the current datagram, 16 bits. This is the sequence number.
• *Flags – A three-bit field in which the two low-order bits control fragmentation. One bit specifies whether the packet can be fragmented, and the other specifies whether the packet is the last fragment in a series of fragmented packets.
• Fragment offset – Used to help piece together datagram fragments, 13 bits. This field allows the previous field to end on a 16-bit boundary.
• *Time-to-live (TTL) – A field that specifies the number of hops a packet may travel. This number is decreased by one as the packet travels through a router. When the counter reaches zero the packet is discarded. This prevents packets from looping endlessly.
• Protocol – indicates which upper-layer protocol, such as TCP or UDP, receives incoming packets after IP processing has been completed, eight bits.
• Header checksum – helps ensure IP header integrity, 16 bits. • IP Source• IP Destination• Options – allows IP to support various options, such as security, variable length. • *Padding – extra zeros are added to this field to ensure that the IP header is always a
multiple of 32 bits.
IP Stuff
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 31
Module 10: Routing Fundamentals and Subnets10.1 Routed Protocol
10.1.1 Routable and routed protocols 10.1.2 IP as a routed protocol 10.1.3 Packet propagation and switching within a router 10.1.4 Internet Protocol (IP) 10.1.5 Anatomy of an IP packet
10.2 IP Routing Protocols10.2.1 Routing overview 10.2.2 Routing versus switching 10.2.3 Routed versus routing 10.2.4 Path determination 10.2.5 Routing tables 10.2.6 Routing algorithms and metrics 10.2.7 IGP and EGP 10.2.8 Link state and distance vector 10.2.9 Routing protocols
10.3 The Mechanics of Subnetting10.3.1 Classes of network IP addresses 10.3.2 Introduction to and reason for subnetting 10.3.3 Establishing the subnet mask address 10.3.4 Applying the subnet mask 10.3.5 Subnetting Class A and B networks 10.3.6 Calculating the resident subnetwork through ANDing
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 32
10.2.1 Routing overview
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 33
10.2.1 Routing overview
The router compares available routing table information to select the best path.
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 34
10.2.1 Routing overview
• Routing metrics are values used in determining the advantage of one route over another. • Routing protocols use various combinations of metrics for determining the best path for data.
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 35
10.2.1 Routing overview
MACd MACs IPs IPd Ps Pd
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 36
10.2.2 Routing versus Switching
Routing is a hierarchical organizational scheme that allows individual addresses to be grouped together; the same as area codes in the telephone network.
• Routers must maintain routing tables and make sure other routers know of changes in the network topology.
• This function is performed using a routing protocol.
• The router must use the routing table to determine where to send packets.
• The router switches the packets to the appropriate interface, adds the necessary framing information for the interface, and then transmits the frame.
016139337917IP address ? Telephone number ? Social Security
Number ?You need a subnet mask to know.
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 37
• This course focuses on Internet Protocol (IP). • Other routable or routed protocols include DecNet,
IPX/SPX, XNS and AppleTalk.• These protocols provide Layer 3 support. • Non-routable protocols do not provide Layer 3
support. • The most common non-routable protocol is
NetBEUI. • NetBEUI is a small, fast, and efficient protocol that
is limited to frame delivery within one segment.
Routable Protocols
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 38
10.2.2 Routing versus Switching 3
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 39
10.2.2 Routing versus Switching
E1 is just another NIC on the network. The router keeps the same arp table as any of the hosts on that network.
On the WAN side, the router keeps a Routing Table.
S1S1
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 40
10.2.2 Routing versus Switching
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 41
• Includes any network protocol that provides enough information in its network layer address for a router to forward it to the next device and thence to its destination.
• Defines the format and use of the fields within a packet.• The Internet Protocol (IP) and Novell's Internetwork Packet Exchange (IPX) are
examples of routed protocols. Other examples include DECnet, AppleTalk, Banyan VINES, and Xerox Network Systems (XNS).
RoutED
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 42
10.2.3 Routed versus routing
RoutING
1. Routing Information Protocol (RIP)2. Interior Gateway Routing Protocol (IGRP)3. Open Shortest Path First (OSPF)4. Border Gateway Protocol (BGP)5. Enhanced IGRP (EIGRP).
Distance Vector
Link State
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 43
Distance Vector
Link State
EGPIGP
IGP
IGP
IGP
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 44
10.2.4 Path determination
• Routes configured manually by the network administrator are static routes. • Routes learned by others routers using a routing protocol are dynamic
routes.
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 45
10.2.4 Path determination
Each intersection is a router
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 46
10.2.4 Path determination
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 47
• Routing Information Protocol (RIP) uses hop count as its only routing metric. • Interior Gateway Routing Protocol (IGRP) uses a combination of bandwidth,
delay, load, and reliability metrics to create a composite metric value.
10.2.5 Routing tables
S0
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 48
10.2.6 Routing algorithms and metrics
• Bandwidth• Delay• Load• Reliability
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 49
10.2.6 Routing algorithms and metrics
1. Bandwidth – The data capacity of a link. Normally, a 10-Mbps Ethernet link is preferable to a 64-kbps leased line.
2. Delay – The length of time required to move a packet along each link from source to destination. Delay depends on the bandwidth of intermediate links, the amount of data that can be temporarily stored at each router, network congestion, and physical distance.
3. Load – The amount of activity on a network resource such as a router or a link. 4. Reliability – Usually a reference to the error rate of each network link. 5. Hop count – The number of routers that a packet must travel through before
reaching its destination. Each router the data must pass through is equal to one hop. A path that has a hop count of four indicates that data traveling along that path would have to pass through four routers before reaching its final destination. If multiple paths are available to a destination, the path with the least number of hops is preferred.
6. Ticks – The delay on a data link using IBM PC clock ticks. One tick is approximately 1/18 second.
7. Cost – An arbitrary value, usually based on bandwidth, monetary expense, or other measurement, that is assigned by a network administrator.
Bad Dogs Love Routing Hairy Tom Cats
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 50
10.2.6 Routing algorithms and metrics
1. Optimization – Optimization describes the capability of the routing algorithm to select the best route. The route will depend on the metrics and metric weightings used in the calculation. For example, one algorithm may use both hop count and delay metrics, but may consider delay metrics as more important in the calculation.
2. Simplicity and low overhead – The simpler the algorithm, the more efficiently it will be processed by the CPU and memory in the router. This is important so that the network can scale to large proportions, such as the Internet.
3. Robustness and stability – A routing algorithm should perform correctly when confronted by unusual or unforeseen circumstances, such as hardware failures, high load conditions, and implementation errors.
4. Flexibility – A routing algorithm should quickly adapt to a variety of network changes. These changes include router availability, router memory, changes in bandwidth, and network delay.
5. Rapid convergence – Convergence is the process of agreement by all routers on available routes. When a network event causes changes in router availability, updates are needed to reestablish network connectivity. Routing algorithms that converge slowly can cause data to be undeliverable.
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 51
10.2.7 IGP and EGP
Interior Gateway Protocols
Exterior Gateway Protocols
(RIP) and (RIPv2) (IGRP) (EIGRP) (OSPF) (IS-IS)
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 52
10.2.8 Link state and distance vector IGPs can be further categorized as either:1. Distance-Vector protocols - RIP IGRP EIGRP
• Routing by rumor2. Link-State protocols.
Link-state advertisements are caused by…
topology changes link-state refresh packets
1. Distance-Vector protocols “Psst! Hey neighbor, remember who I know about?”
2. Link-State protocols. “Listen up everybody, there’s a change to the networks that I’m connected to.”
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 53
Module 10: Routing Fundamentals and Subnets10.1 Routed Protocol
10.1.1 Routable and routed protocols 10.1.2 IP as a routed protocol 10.1.3 Packet propagation and switching within a router 10.1.4 Internet Protocol (IP) 10.1.5 Anatomy of an IP packet
10.2 IP Routing Protocols10.2.1 Routing overview 10.2.2 Routing versus switching 10.2.3 Routed versus routing 10.2.4 Path determination 10.2.5 Routing tables 10.2.6 Routing algorithms and metrics 10.2.7 IGP and EGP 10.2.8 Link state and distance vector 10.2.9 Routing protocols
10.3 The Mechanics of Subnetting10.3.1 Classes of network IP addresses 10.3.2 Introduction to and reason for subnetting 10.3.3 Establishing the subnet mask address 10.3.4 Applying the subnet mask 10.3.5 Subnetting Class A and B networks 10.3.6 Calculating the resident subnetwork through ANDing
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 54
10.3.1 Classes of network IP addresses
EG: An IP address 172.32.65.13 and a default subnet mask, the host belongs to the 172.32.0.0 network.
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 55
10.3.2 Introduction to and reason for subnetting
The benefits of Subnetting1. smaller broadcast domains 2. low-level security provided 3. increased address flexibility
EG: In a class C network a subnet mask of 255.255.255.224 will create 6 useable subnets each with 32 useable hosts.
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 56
10.3.2 Introduction to and reason for subnetting
Host bits are reassigned as network bits.
• Host bits of the network address are all equal to 0.
• Host bits of the broadcast address are all equal to 1.
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 57
10.3.2 Introduction to and reason for subnetting
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 58
10.3.3 Establishing the subnet mask address
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 59
10.3.3 Establishing the subnet mask address
Assume Class C subnetting
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 60
10.3.3 Establishing the subnet mask address
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 61
10.3.3 Establishing the subnet mask address
Magic Numbers
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 62
10.3.4 Applying the subnet mask
Assumes subnet mask of 255.255.255.224 resulting
in a magic number = 32
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 63
10.3.4 Applying the subnet mask
Magic Numbers
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 64
10.3.5 Subnetting Class A and B networks
16 bits are available for Class B host IP addresses using the default subnet mask.
If you applied the subnet mask 255.255.255.0 to a Class B network it would give you 254
useable subnets and 254 useable hosts/subnet.
Applying the subnet mask 255.255.255.240 (/28) to a Class B network will give 4094 useable
subnets and 14 useable hosts/subnet.
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 65
10.3.5 Subnetting Class A and B networks
To borrow 20 bits you would use subnet mask 255.255.255.240 = /28
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 66
10.3.5 Subnetting Class A and B networks
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 67
10.3.5 Subnetting Class A and B networks
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 68
10.3.5 Subnetting Class A and B networks
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 69
10.3.6 Calculating the resident subnetwork through ANDing
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 70
10.3.6 Calculating the resident subnetwork through ANDing
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 71
Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod10 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 72
FIN