Download Class A and B IP addresses

CCNP 1 v3.0 Module 2
Advanced IP Addressing
Management
Cisco Networking Academy
© 2003, Cisco Systems, Inc. All rights reserved.
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Objectives
• IPv4 Addressing
• IP Addressing Crisis and Solutions
• VLSM
• Route Summarization
• Private Addressing and NAT
• IP Unnumbered
• DHCP and Easy IP
• Helper Addresses
• IPv6
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Address Architecture of the Internet
Dotted Decimal Notation
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Class A and B IP addresses
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IPv4 Address Classes
1st octet
2nd octet
3rd octet
4th octet
Class A
Network
Host
Host
Host
Class B
Network Network
Host
Host
Class C
Network Network Network
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Host
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IP Addresses Available to Internet Hosts
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One Problem - No Medium Size
• 16 million
• 65,536
• 256
For most organizations, 256 is too small a
limit on hosts, yet 65,536 is far too many.
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The Subnet Mask
• The solution to the IP address shortage
was thought to be the subnet mask.
• Formalized in 1985 (RFC 950), the subnet
mask breaks a single class A, B or C
network in to smaller pieces.
Subnetting
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Subnet Masking
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IP Addressing Crisis
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Classless Interdomain Routing (CIDR)
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Variable-Length Subnet Masks (VLSM)
• VLSM allows an organization to use more than
one subnet mask within the same network
address space.
• Implementing VLSM is often referred to as
subnetting a subnet and it can be used to
maximize addressing efficiency.
• Over the past 20 years, network engineers have
developed three critical strategies for efficiently
addressing point-to-point WAN links:
Use VLSM
Use private addressing (RFC 1918)
Use IP unnumbered
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Enabling the use of subnet 0
• The Cisco IOS allows you to use subnet 0.
On pre-IOS 12.x releases, this feature is
not enabled by default:
router(config)#ip subnet-zero
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Using the all-ones subnet
• Although this Cisco IOS will allow you to
configure addresses in the all-ones
subnet.
• Some literature still states that, as a
general rule, you should not use the allones subnet.
However, it is perfectly legal to use these
addresses according to the RFCs.
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Classless and Classful Routing Protocols
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Supernetting and Address Allocation
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Route Aggregation and Supernetting
1st octet
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2nd octet
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Route Summarization
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Private IP Addresses (RFC 1918)
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Discontiguous Subnets
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Network Address Translation (NAT)
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Using IP Unnumbered
168.71.8.0/24
168.71.5.0/24
This is fine as long as both of the routers have a route for
the address used for in the unnumbered configuration.
•Default routes will work too
These ‘unnumbered’ addresses do not need to be on the same subnet
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DHCP Overview: Step 1
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DHCP Overview: Step 2
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DHCP Operation
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Key DHCP Server Commands
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Key Commands for Monitoring DHCP
Operation
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Easy IP
• Easy IP is a combination suite of Cisco IOS features that
allows a router to negotiate its own IP address and to do
NAT through that negotiated address.
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Easy IP
• Easy IP is a combination suite of Cisco IOS
features that allows a router to negotiate its own
IP address and to do NAT through that
negotiated address.
• Easy IP is typically deployed on a small office,
home office (SOHO) router.
• It is useful in cases where a small LAN connects
to the Internet by way of a provider that
dynamically assigns only one IP address for the
entire remote site.
– DHCP or PPPoE
http://www.cisco.com/warp/public/cc/pd/iosw/ioft/ionetn/tech/ezip1_wp.htm
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Purpose of Helper Addresses
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Default Forwarded UDP Services
Router(config-if)#exi
To add a forwarded protocol
Router(config)#ip forward-protocol ?
nd
Sun's Network Disk protocol
sdns
Network Security Protocol
spanning-tree Use transparent bridging to flood UDP broadcasts
turbo-flood
Fast flooding of UDP broadcasts
udp
Packets to a specific UDP port
Router(config)#ip forward-protocol udp 571
Router(config)#no ip forward-protocol udp 69
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IP Helper Address Example
Router(config)#int fa0/1
Router(config-if)#ip helper-address 172.24.1.9
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IP Address Issues Solutions
Growth of Routing Tables
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Long-term solution: IPv6
• IP v6, or IPng (IP – the Next Generation)
uses a 128-bit address space, yielding
340,282,366,920,938,463,463,374,607,431,768,211,456
possible addresses.
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IPv6
•
IPv6 has been slow to arrive
– IPv4 revitalized by new features, making
IPv6 a luxury, and not a desperately needed
fix
•
(RFC 1918 address, VLSM)
– IPv6 requires new software; IT staffs must
be retrained
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IPv6
• IPv6 will most likely coexist with IPv4 for
years to come.
Some experts believe IPv4 will remain for more
than 10 more years.
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IPv6 address format
• IPv6 can be written as 32 hex digits, with colons
separating the values of the eight 16-bit pieces of
the address:
FEDC:BA98:7654:3210:FEDC:BA98:7654:3210
http://www.faqs.org/rfcs/rfc1884.html
http://www.faqs.org/rfcs/rfc2373.html
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IPv6 address format
Because IPv6 addresses, especially in the early
implementation phase, may contain consecutive
16-bit values of zero, one such string of 0s per
address can be omitted and replaced by a double
colon, so this:
1080:0:0:0:8:800:200C:417A
can be shortened to become this:
1080::8:800:200C:417A
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IPv6 Loopback address
0:0:0:0:0:0:0:1
(the IPv6 loopback address)
Can be written list this:
: :1
http://playground.sun.com/pub/ipng/html/INET-IPng-Paper.html
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IPv6 Address Format
• Three general types of addresses:
Unicast
Anycast
Mulicast
• IPv6 global unicast addresses feature three
levels of hierarchy:
Public topology
Site topology
Interface Identifier
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IPv6 Address format
• Unicast: An identifier for a single interface.
• Anycast: An identifier for a set of interfaces
(typically belonging to different nodes). A packet
sent to an anycast address is delivered to the
“nearest,” or first, interface in the anycast group.
• Multicast: An identifier for a set of interfaces
(typically belonging to different nodes). A packet
sent to a multicast address is delivered to all
interfaces in the multicast group.
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IPv6 address format
IPv6 address has three levels of hierarchy
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Summary
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