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Chapter 8
Interconnecting
Networks with
TCP/IP
© 1999, Cisco Systems, Inc.
8-1
Objectives
Upon completion of this chapter you will
be able to perform the following tasks:
• Identify the IP protocol stack, its protocol layer
functions, and commonly used IP protocols
• Identify IP address classes, IP addresses, IP subnet
masks, IP network numbers, subnet numbers, and
possible host numbers.
• Configure IP addresses and subnet masks on a
router interface and optionally configure a host table.
• Interconnect the VLANs with a layer three device
such as a router on a stick.
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-3
Introduction to TCP/IP
Host
Host
Internet
TCP/IP
Early protocol suite
Universal
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-4
TCP/IP Protocol Stack
7
Application
6
Presentation
5
Session
4
Transport
Transport
3
Network
Internet
2
Data Link
Data Link
5
Application
4
3
2
1
1
Physical
© 1999, Cisco Systems, Inc.
Physical
www.cisco.com
ICND—8-5
Application Layer Overview
Application
Transport
Internet
Data Link
File Transfer
- TFTP *
- FTP *
- NFS
E-Mail
- SMTP
Remote Login
- Telnet *
- rlogin *
Network Management
- SNMP *
Name Management
- DNS*
*Used by the router
Physical
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-6
Transport Layer Overview
Application
Transport
Transmission Control
Protocol (TCP)
ConnectionOriented
User Datagram
Protocol (UDP)
Connectionless
Internet
Data Link
Physical
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-7
TCP Segment Format
Bit 0
Bit 15 Bit 16
Bit 31
Destination port (16)
Source port (16)
Sequence number (32)
Acknowledgement number (32)
Header
length (4)
Reserved (6) Code bits (6)
Checksum (16)
20
Bytes
Window (16)
Urgent (16)
Options (0 or 32 if any)
Data (varies)
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-8
Port Numbers
Application
Layer
Transport
Layer
© 1999, Cisco Systems, Inc.
F
T
P
T
E
L
N
E
T
S
M
T
P
D
N
S
T
F
T
P
S
N
M
P
R
I
P
21
23
25
53
69
161
520
Port
Numbers
UDP
TCP
www.cisco.com
ICND—8-9
TCP Port Numbers
Source
Port
Dest.
Port
…
Telnet Z
Host Z
Host A
© 1999, Cisco Systems, Inc.
SP
DP
1028
23
…
www.cisco.com
Dest. port = 23.
Send packet to my
Telnet
application.
ICND—8-10
TCP Three Way
Handshake/Open Connection
Host A
1
Host B
Send SYN
(seq=100 ctl=SYN)
SYN received
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-11
TCP Three Way
Handshake/Open Connection
Host A
1
Host B
Send SYN
(seq=100 ctl=SYN)
SYN received
Send SYN, ACK 2
(seq=300 ack=101 ctl=syn,ack)
SYN received
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-12
TCP Three Way
Handshake/Open Connection
Host A
1
Host B
Send SYN
(seq=100 ctl=SYN)
SYN received
Send SYN, ACK 2
(seq=300 ack=101 ctl=syn,ack)
SYN received
3
Established
(seq=101 ack=301 ctl=ack)
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-13
TCP Simple Acknowledgment
Sender
Receiver
Window size = 1
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-14
TCP Simple Acknowledgment
Sender
Receiver
Send 1
Receive 1
Window size = 1
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-15
TCP Simple Acknowledgment
Sender
Receiver
Send 1
Receive 1
Send ACK 2
Receive ACK 2
Window size = 1
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-16
TCP Simple Acknowledgment
Sender
Receiver
Send 1
Receive 1
Send ACK 2
Receive ACK 2
Send 2
Receive 2
Window size = 1
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-17
TCP Simple Acknowledgment
Sender
Receiver
Send 1
Receive 1
Send ACK 2
Receive ACK 2
Send 2
Receive 2
Send ACK 3
Receive ACK 3
Window size = 1
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-18
TCP Simple Acknowledgment
Sender
Receiver
Send 1
Receive 1
Send ACK 2
Receive ACK 2
Send 2
Receive 2
Send ACK 3
Receive ACK 3
Send 3
Receive 3
Window size = 1
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-19
TCP Simple Acknowledgment
Sender
Receiver
Send 1
Receive 1
Send ACK 2
Receive ACK 2
Send 2
Receive 2
Send ACK 3
Receive ACK 3
Send 3
Receive 3
Send ACK 4
Receive ACK 4
Window size = 1
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-20
TCP Sequence and
Acknowledgment Numbers
Source
Port
Dest.
Port
Sequence
#
Acknowledgement
#
…
I just
sent #10.
Source Dest. Seq. Ack.
1028
23
© 1999, Cisco Systems, Inc.
10
1
www.cisco.com
ICND—8-21
TCP Sequence and
Acknowledgment Numbers
Source
Port
Dest.
Port
Sequence
#
Acknowledgement
#
I just
sent #10.
…
I just got #10,
now I need #11.
Source Dest. Seq. Ack.
1028
23
10
1
Source Dest. Seq. Ack.
23
1028
1
11
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-22
TCP Sequence and
Acknowledgment Numbers
Source
Port
Dest.
Port
Sequence
#
Acknowledgement
#
I just
sent #11.
…
I just got #10,
now I need #11.
Source Dest. Seq. Ack.
1028
23
10
1
Source Dest. Seq. Ack.
23
1028
1
11
Source Dest. Seq. Ack.
1028
23
© 1999, Cisco Systems, Inc.
11
2
www.cisco.com
ICND—8-23
TCP Sequence and
Acknowledgment Numbers
Source
Port
Dest.
Port
Sequence
#
Acknowledgement
#
I just
sent #11.
…
I just got #11,
now I need #12.
Source Dest. Seq. Ack.
1028
23
10
1
Source Dest. Seq. Ack.
23
1028
1
11
Source Dest. Seq. Ack.
1028
23
11
2
Source Dest. Seq. Ack.
23
1028
2
12
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-24
TCP Windowing
Sender
© 1999, Cisco Systems, Inc.
Receiver
www.cisco.com
ICND—8-25
TCP Windowing
Sender
Window size = 3
Send 1
Receiver
Window size = 3
Send 2
Window size = 3
Send 3
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-26
TCP Windowing
Sender
Window size = 3
Send 1
Receiver
Window size = 3
Send 2
Window size = 3
Send 3
© 1999, Cisco Systems, Inc.
ACK 3
Window size = 2
www.cisco.com
Packet 3 is
Dropped
ICND—8-27
TCP Windowing
Sender
Window size = 3
Send 1
Receiver
Window size = 3
Send 2
Window size = 3
Send 3
ACK 3
Window size = 2
Packet 3 is
Dropped
Window size = 3
Send 3
Window size = 3
Send 4
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-28
TCP Windowing
Sender
Window size = 3
Send 1
Receiver
Window size = 3
Send 2
Window size = 3
Send 3
Packet 3 is
ACK 3
Window size = 2 Dropped
Window size = 3
Send 3
Window size = 3
Send 4
ACK 5
Window size = 2
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-29
UDP Segment Format
Bit
1 0
Bit 15 Bit 16
Bit 31
Destination port (16)
Source port (16)
Length (16)
8
Bytes
Checksum (16)
Data (if any)
No sequence or acknowledgment fields
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-30
Internet Layer Overview
Internet Protocol (IP)
Application
Transport
Internet
Internet Control Message
Protocol (ICMP)
Address Resolution
Protocol (ARP)
Data Link
Physical
Reverse Address
Resolution Protocol (RARP)
OSI network layer corresponds to the
TCP/IP internet layer
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-31
IP Datagram
Bit
1 0
Version
(4)
Bit 15 Bit 16
Header
Length (4)
Priority & Type
of Service (8)
Total Length (16)
Flags
(3)
Identification (16)
Time to live (8)
Bit 31
Protocol (8)
Fragment offset (13)
Header checksum (16)
20
Bytes
Source IP Address (32)
Destination IP Address (32)
Options (0 or 32 if any)
Data (varies if any)
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-32
Protocol Field
Transport
Layer
UDP
TCP
6
Internet
Layer
17
Protocol
Numbers
IP
Determines destination upper-layer protocol
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-33
Internet Control Message
Protocol
Application
Destination
Unreachable
Transport
1
ICMP
Echo (Ping)
Internet
Other
Data Link
Physical
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-34
Address Resolution Protocol
I need the
Ethernet
address of
176.16.3.2.
172.16.3.1
172.16.3.2
IP: 172.16.3.2 = ???
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-35
Address Resolution Protocol
I need the
Ethernet
address of
176.16.3.2.
I heard that broadcast.
The message is for me.
Here is my Ethernet
address.
172.16.3.1
172.16.3.2
IP: 172.16.3.2 = ???
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-36
Address Resolution Protocol
I need the
Ethernet
address of
176.16.3.2.
I heard that broadcast.
The message is for me.
Here is my Ethernet
address.
172.16.3.1
172.16.3.2
IP: 172.16.3.2 = ???
IP: 172.16.3.2
Ethernet: 0800.0020.1111
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-37
Address Resolution Protocol
I need the
Ethernet
address of
176.16.3.2.
I heard that broadcast.
The message is for me.
Here is my Ethernet
address.
172.16.3.1
172.16.3.2
IP: 172.16.3.2 = ???
IP: 172.16.3.2
Ethernet: 0800.0020.1111
Map IP
© 1999, Cisco Systems, Inc.
Ethernet
Local ARP
www.cisco.com
ICND—8-38
Reverse ARP
What is
my IP
address?
Ethernet: 0800.0020.1111 IP = ???
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-39
Reverse ARP
I heard that
broadcast.
Your IP
address is
172.16.3.25.
What is
my IP
address?
Ethernet: 0800.0020.1111 IP = ???
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-40
Reverse ARP
I heard that
broadcast.
Your IP
address is
172.16.3.25.
What is
my IP
address?
Ethernet: 0800.0020.1111 IP = ???
Ethernet: 0800.0020.1111
IP: 172.16.3.25
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-41
Reverse ARP
I heard that
broadcast.
Your IP
address is
172.16.3.25.
What is
my IP
address?
Ethernet: 0800.0020.1111 IP = ???
Ethernet: 0800.0020.1111
IP: 172.16.3.25
Map Ethernet
© 1999, Cisco Systems, Inc.
www.cisco.com
IP
ICND—8-42
Introduction to TCP/IP
Addresses
172.18.0.1
172.18.0.2
10.13.0.0
10.13.0.1
172.16.0.1
HDR SADA DATA
172.17.0.1
172.16.0.2
172.17.0.2
192.168.1.0
192.168.1.1
• Unique addressing allows communication
between end stations
• Path choice is based on location
Location is represented by an address
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-43
IP Addressing
32 bits
Dotted
Decimal
Maximum
© 1999, Cisco Systems, Inc.
Network
255
255
www.cisco.com
Host
255
255
ICND—8-44
IP Addressing
32 bits
Dotted
Decimal
Network
© 1999, Cisco Systems, Inc.
16 17
255
24 25
32
11111111 11111111
11111111 11111111
128
64
32
16
8
4
2
1
128
64
32
16
8
4
2
1
8 9
255
128
64
32
16
8
4
2
1
128
64
32
16
8
4
2
1
1
Binary
255
255
Maximum
Host
www.cisco.com
ICND—8-45
IP Addressing
32 bits
Dotted
Decimal
Network
16 17
255
24 25
32
11111111 11111111
11111111 11111111
128
64
32
16
8
4
2
1
128
64
32
16
8
4
2
1
8 9
255
128
64
32
16
8
4
2
1
128
64
32
16
8
4
2
1
1
Binary
255
255
Maximum
Host
Example
172
16
122
204
Decimal
Example 10101100 00010000 01111010 11001100
Binary
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-46
IP Address Classes
8 bits
8 bits
8 bits
8 bits
Host
Host
Host
Host
Host
Class A:
Network
Class B:
Network Network
Class C:
Network Network Network
Class D:
Multicast
Class E:
Research
© 1999, Cisco Systems, Inc.
www.cisco.com
Host
ICND—8-47
IP Address Classes
Bits:
Class A:
Bits:
Class B:
Bits:
Class C:
Bits:
Class D:
© 1999, Cisco Systems, Inc.
1
8 9
0NNNNNNN
16 17
24 25
Host
Host
32
Host
Range (1-126)
1
8 9
10NNNNNN
16 17
Network
Range (128-191)
1
8 9
110NNNNN
Host
16 17
Network
Range (192-223)
1
8 9
1110MMMM
24 25
Host
24 25
Network
16 17
32
32
Host
24 25
32
Multicast Group Multicast Group Multicast Group
Range (224-239)
www.cisco.com
ICND—8-48
Host Addresses
172.16.2.1
10.1.1.1
10.6.24.2
E1
172.16.3.10
E0
172.16.2.1
10.250.8.11
172.16.12.12
172.16
Network
© 1999, Cisco Systems, Inc.
.
12 . 12
Host
10.180.30.118
Routing Table
Network
Interface
172.16.0.0
E0
10.0.0.0
E1
www.cisco.com
ICND—8-49
Determining Available Host
Addresses
Network
0
0
© 1999, Cisco Systems, Inc.
...
...
10101100 00010000 00000000 00000000
00000000 00000001
00000000 00000011
N
1
2
3
...
16
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
172
Host
11111111 11111101
11111111 11111110
11111111 11111111
65534
65535
65536
2
2N-2 = 216-2 = 65534
65534
www.cisco.com
ICND—8-50
IP Address Classes Exercise
Address
Class
Network
Host
10.2.1.1
128.63.2.100
201.222.5.64
192.6.141.2
130.113.64.16
256.241.201.10
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-51
IP Address Classes Exercise
Answers
Address
Class
10.2.1.1
A
10.0.0.0
0.2.1.1
128.63.2.100
B
128.63.0.0
0.0.2.100
201.222.5.64
C
201.222.5.0
0.0.0.64
192.6.141.2
C
192.6.141.0
0.0.0.2
130.113.64.16
B
130.113.0.0
0.0.64.16
256.241.201.10
© 1999, Cisco Systems, Inc.
Network
Host
Nonexistent
www.cisco.com
ICND—8-52
Addressing without Subnets
172.16.0.1 172.16.0.2 172.16.0.3
172.16.255.253 172.16.255.254
…...
172.16.0.0
Network 172.16.0.0
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-53
Addressing with Subnets
172.16.3.0
172.16.4.0
172.16.1.0
172.16.2.0
Network 172.16.0.0
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-54
Subnet Addressing
172.16.2.200
172.16.3.5
172.16.3.1
E1
172.16.2.2
E0
172.16.2.1
172.16.3.100
172.16.2.160
172.16
Network
© 1999, Cisco Systems, Inc.
.
172.16.3.150
2 . 160
New Routing Table
Network
Interface
Host
172.16.0.0
E0
172.16.0.0
E1
www.cisco.com
ICND—8-55
Subnet Addressing
172.16.2.200
172.16.3.5
172.16.3.1
E1
E0
172.16.2.1
172.16.2.2
172.16.3.100
172.16.2.160
172.16
Network
© 1999, Cisco Systems, Inc.
.
2
172.16.3.150
.
160
Subnet Host
New Routing Table
Network
Interface
172.16.2.0
E0
172.16.3.0
E1
www.cisco.com
ICND—8-56
Subnet Mask
Network
IP
Address
172
Host
16
0
Network
Default
Subnet
Mask
8-bit
Subnet
Mask
© 1999, Cisco Systems, Inc.
255
0
Host
255
0
0
11111111
11111111
00000000
00000000
Also written as “/16” where 16 represents the number of 1s
in the mask.
Network
Subnet
Host
255
255
255
0
Also written as “/24” where 24 represents the number of 1s
in the mask.
www.cisco.com
ICND—8-57
Decimal Equivalents of Bit
Patterns
128 64
32
16
8
4
2
1
1
0
0
0
0
0
0
0
=
128
1
1
0
0
0
0
0
0
=
192
1
1
1
0
0
0
0
0
=
224
1
1
1
1
0
0
0
0
=
240
1
1
1
1
1
0
0
0
=
248
1
1
1
1
1
1
0
0
=
252
1
1
1
1
1
1
1
0
=
254
1
1
1
1
1
1
1
1
=
255
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-58
Subnet Mask without Subnets
Network
Host
172.16.2.160
10101100
00010000
00000010
10100000
255.255.0.0
11111111
11111111
00000000
00000000
10101100
00010000
00000000
00000000
172
16
0
0
Network
Number
Subnets not in use—the default
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-59
Subnet Mask with Subnets
Network
172.16.2.160
Host
10101100
00010000
00000010
10100000
11111111
11111111
11111111
00000000
10101100
00010000
00000010
00000000
172
16
128
192
224
240
248
252
254
255
255.255.255.0
Subnet
Network
Number
2
0
Network number extended by eight bits
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-60
Subnet Mask with Subnets
(cont.)
255.255.255.192
Network
Number
Host
10101100
00010000
00000010
10100000
11111111
11111111
11111111
11000000
10101100
00010000
00000010
10000000
128
192
224
240
248
252
254
255
172.16.2.160
Subnet
128
192
224
240
248
252
254
255
Network
172
16
2
128
Network number extended by ten bits
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-61
Subnet Mask Exercise
Address
Subnet Mask
172.16.2.10
255.255.255.0
10.6.24.20
255.255.240.0
10.30.36.12
255.255.255.0
© 1999, Cisco Systems, Inc.
www.cisco.com
Class
Subnet
ICND—8-62
Subnet Mask Exercise
Answers
Address
Subnet Mask
Class
Subnet
172.16.2.10
255.255.255.0
B
172.16.2.0
10.6.24.20
255.255.240.0
A
10.6.16.0
10.30.36.12
255.255.255.0
A
10.30.36.0
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-63
Broadcast Addresses
172.16.3.0
172.16.4.0
172.16.1.0
172.16.2.0
172.16.3.255
(Directed broadcast)
255.255.255.255
(Local network broadcast)
X
172.16.255.255
(All subnets broadcast)
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-64
Addressing Summary
Example
172.16.2.160
172
16
10101100
00010000
2
160
00000010 10100000 Host
1
Mask
255.255.255.192
Subnet 4
Broadcast
First
Last
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-65
Addressing Summary
Example
172.16.2.160
255.255.255.192
172
16
10101100
00010000
11111111
11111111
2
160
00000010 10100000 Host
1
11111111 11000000 Mask 2
Subnet
Broadcast
First
Last
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-66
Addressing Summary
Example
172
16
2
160
3
172.16.2.160
255.255.255.192
10101100
00010000
11111111
11111111
00000010 10100000 Host
1
11111111 11000000 Mask 2
Subnet
Broadcast
First
Last
© 1999, Cisco Systems, Inc.
www.cisco.com
7
ICND—8-67
Addressing Summary
Example
172
16
2
160
3
172.16.2.160
255.255.255.192
10101100
00010000
11111111
11111111
00000010 10100000 Host
1
11111111 11000000 Mask 2
10000000 Subnet 4
Broadcast
First
Last
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-68
Addressing Summary
Example
172
16
2
160
3
172.16.2.160
255.255.255.192
10101100
00010000
11111111
11111111
00000010 10100000 Host
1
11111111 11000000 Mask 2
10000000 Subnet 4
10111111 Broadcast
5
First
6
Last
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-69
Addressing Summary
Example
172
16
2
160
3
172.16.2.160
255.255.255.192
10101100
00010000
11111111
11111111
00000010 10100000 Host
1
11111111 11000000 Mask 2
10000000 Subnet 4
10111111 Broadcast
5
10000001 First
6
Last
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-70
Addressing Summary
Example
172
16
2
160
3
172.16.2.160
255.255.255.192
10101100
00010000
11111111
11111111
00000010 10100000 Host
1
11111111 11000000 Mask 2
10000000 Subnet 4
10111111 Broadcast
© 1999, Cisco Systems, Inc.
www.cisco.com
5
10000001 First
6
10111110 Last
7
ICND—8-71
Addressing Summary
Example
172
16
2
160
3
172.16.2.160
255.255.255.192
10101100
00010000
00000010 10100000 Host
11111111
11111111
11111111 11000000 Mask 2
10101100
00010000
00000010 10000000 Subnet 4
10101100
00010000
00000010 10111111 Broadcast
10101100
00010000
5
00000010 10000001 First
6
10101100
00010000
00000010 10111110 Last
7
1
8
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-72
Addressing Summary
Example
172
16
2
160
3
10101100
00010000
255.255.255.192 11111111
8
9
172.16.2.128
10101100
11111111
11111111 11000000 Mask 2
00010000
00000010 10000000 Subnet 4
10101100
00010000
00000010 10111111 Broadcast
6
7
172.16.2.160
172.16.2.191
00000010 10100000 Host
172.16.2.129
10101100
00010000
5
00000010 10000001 First
172.16.2.190
10101100
00010000
00000010 10111110 Last
© 1999, Cisco Systems, Inc.
www.cisco.com
1
ICND—8-73
Class B Subnet Example
IP Host Address: 172.16.2.121
Subnet Mask: 255.255.255.0
Network
Network
Subnet
Host
172.16.2.121: 10101100
00010000
00000010
01111001
255.255.255.0: 11111111
11111111
11111111
00000000
Subnet: 10101100
00010000
00000010
00000000
Broadcast: 10101100
00010000
00000010
11111111
Subnet Address = 172.16.2.0
Host Addresses = 172.16.2.1–172.16.2.254
Broadcast Address = 172.16.2.255
Eight bits of subnetting
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-74
Subnet Planning
20 subnets
5 hosts per subnet
Class C address:
192.168.5.0
192.168.5.16
Other
subnets
192.168.5.32
© 1999, Cisco Systems, Inc.
192.168.5.48
www.cisco.com
ICND—8-75
Class C Subnet Planning
Example
IP Host Address: 192.168.5.121
Subnet Mask: 255.255.255.248
Network
Network
Network Subnet Host
192.168.5.121: 11000000
10101000
00000101
01111001
255.255.255.248: 11111111
11111111
11111111
11111000
Subnet: 11000000
Broadcast: 11000000
10101000
00000101
01111000
10101000
00000101
01111111
Subnet Address = 192.168.5.120
Host Addresses = 192.168.5.121–192.168.5.126
Broadcast Address = 192.168.5.127
Five Bits of Subnetting
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-76
Broadcast Addresses Exercise
Address
Subnet Mask
201.222.10.60
255.255.255.248
15.16.193.6
255.255.248.0
128.16.32.13
255.255.255.252
153.50.6.27
255.255.255.128
© 1999, Cisco Systems, Inc.
Class
www.cisco.com
Subnet
Broadcast
ICND—8-77
Broadcast Addresses Exercise
Answers
Address
Subnet Mask
Class
Subnet
Broadcast
201.222.10.60 255.255.255.248
C
201.222.10.56
201.222.10.63
15.16.193.6
255.255.248.0
A
15.16.192.0
15.16.199.255
128.16.32.13
255.255.255.252
B
128.16.32.12
128.16.32.15
153.50.6.27
255.255.255.128
B
153.50.6.0
153.50.6.127
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-78
Switch IP Address
Configuration
Switch(config)#ip address ip-address subnet-mask
• Assigns an address and subnet mask
• Starts IP processing on a switch
Switch(config)#ip default-gateway ip-address
• Specifies a default gateway
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-79
Router IP Address
Configuration
Router(config-if)#ip address ip-address subnet-mask
• Assigns an address and subnet mask
• Starts IP processing on a router interface
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-80
Router IP Address
Configuration
Router#term ip netmask-format {bitcount|
decimal | hexadecimal}
• Sets display format of network mask for
current session
Router(config-line)#ip netmask-format
{bitcount | decimal | hexadecimal}
• Sets format of network mask for a
specific line
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-81
Router IP Host Names
Router(config)#ip host name [tcp-port-number]
address [address]
• Defines static host name to IP address
mapping
ip host Norine 172.16.3.1
ip host Roger 172.16.4.3
192.168.3.1
• Hosts/interfaces selectable by name or IP
address
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-82
Router Name Server
Configuration
DNS Server
Router(config)#ip name-server server-address1
[[server-address2]...[server-address6]]
• Specifies one or more hosts that supply
host name to logical address resolution
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-83
Router Name System
Router(config)#ip domain-lookup
Router(config)#end
Router#pat
Translating ”pat"...domain server (255.255.255.255)
% Unknown command or computer name, or unable to find computer address
Router#config t
Router(config)#no ip domain-lookup
Router(config)#end
Router#pat
Translating ”pat"
% Unknown command or computer name, or unable to find computer address
Router#
DNS enabled by default
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-84
Router Display Host Names
Router#show hosts
Default domain is not set
Name/address lookup uses domain service
Name servers are 255.255.255.255
Host
Norine
Roger
Frank
Bob
Flags
(perm,
(perm,
(perm,
(perm,
OK)
OK)
OK)
OK)
Age Type
0
IP
0
IP
0
IP
0
IP
Address(es)
172.16.100.100
172.16.100.101
172.16.200.200
172.16.200.201
Shows the host table
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-85
VLAN to VLAN Overview
Fast
E0/0
ISL
VLAN 1
Router on
a stick
VLAN 2
Application
10.1.1.2
10.2.2.2
TCP
IP
ISL
Ethernet
Network layer devices combine multiple broadcast domains
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-86
Dividing a Physical Interface
into Subinterfaces
FastEthernet 0/0
FastEthernet 0/0.1
FastEthernet 0/0.2
FastEthernet 0/0.3
Physical interfaces can be divided into
multiple subinterfaces
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-87
ISL Encapsulation
Router(config-subif)#encapsulation isl domain
Enables ISL on a subinterface
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-88
Routing Between VLANs
Fast
E0/0
ISL
VLAN 1
10.1.1.2
© 1999, Cisco Systems, Inc.
VLAN 2
10.2.2.2
interface fastethernet 0/0
no ip address
!
interface fastethernet 0/0.1
ip address 10.1.1.1 255.255.255.0
encapsulation isl 1
interface fastethernet 0/0.2
ip address 10.2.2.1 255.255.255.0
encapsulation isl 2
www.cisco.com
ICND—8-89
Routing Between WANS
ISL
S0
172.16.1.1
VLAN 1
10.1.1.2
VLAN 2
Application
10.2.2.2
interface Serial0
ip address 172.16.1.1 255.255.255.0
© 1999, Cisco Systems, Inc.
172.16.1.2
www.cisco.com
TCP
IP
HDLC
Serial
ICND—8-90
Visual Objective
SUBNET
10.1.1.0
10.2.2.0
10.3.3.0
10.4.4.0
10.5.5.0
10.6.6.0
10.7.7.0
10.8.8.0
10.9.9.0
10.10.10.0
10.11.11.0
10.12.12.0
10.13.13.0
VLAN
1
2
3
4
5
6
7
8
9
10
11
12
13
POD
wg_ro_x, wg_sw_x, core_sw_a, core_sw_b
wg_pc_a, core_server, core_ro
wg_pc_b, core_server, core_ro
wg_pc_c, core_server, core_ro
wg_pc_d, core_server, core_ro
wg_pc_e, core_server, core_ro
wg_pc_f, core_server, core_ro
wg_pc_g, core_server, core_ro
wg_pc_h, core_server, core_ro
wg_pc_i, core_server, core_ro
wg_pc_j, core_server, core_ro
wg_pc_k, core_server, core_ro
wg_pc_l, core_server, core_ro
VLAN2
fa0/26
e0/1
(port A)
VLAN13
fa0/23
fa0/27
(port B)
...
fa0/1
fa0/24
© 1999, Cisco Systems, Inc.
wg_pc_l
10.13.13.12
wg_sw_l
10.1.1.120
fa0/0
core_ server
fa0/27
(port B)
wg_sw_a
10.1.1.10
fa0/26 e0/1
(port A)
Core_ro
wg_pc_a
10.2.2.12
fa0/12
fa0/13
core_sw_a fa0/14
10.1.1.2
www.cisco.com
fa0/12
fa0/13
fa0/1
fa0/14 core_sw_b
10.1.1.4
ICND—8-91
Summary
After completing this chapter, you should be
able to perform the following tasks:
• Identify the TCP/IP protocol stack and the
functions of each layer
• Separate an IP address into its subcomponents:
the network, subnet, and host portions
• Configure IP addresses on Cisco router and
switch interfaces
• Interconnect VLANs using a layer three device
such as a “router on a stick”
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-92
Review Questions
1. What is the difference between the TCP and
UDP transport layer protocols?
2. Given a host with IP address, 192.168.20.1
255.255.255.240, how many other hosts can
you have in that network?
3. What is required to interconnect separate
VLANs?
© 1999, Cisco Systems, Inc.
www.cisco.com
ICND—8-93