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CCNP Routing
Semester 5
Chapter 2
IP Addressing
IP Addressing Summary
• IP address is 32 bits long
• Network/host boundary can be anywhere in
the 32 bits
• The Internet allocates a unique bit pattern
• Internet authority ARIN will provide the left
portion of the address
• Network mask is the identification of the
bits allocated to the network
CIDR Solves the Following
Problems
• Address exhaustion was solved; the Internet
was running out of numbers
• Network resources required to manage huge
routing tables were becoming untenable
Multicasting Addresses
•
•
•
•
224.0.0.5
224.0.0.6
224.0.0.9
224.0.0.10
All OSPF routers
All OSPF designated routers (DRs)
All RIP2 routers
All EIGRP routers
IPv6 Address Format
• Unicast – An identifier for a single interface
– A packet sent to a unicast address is delivered to the
interface identified by that address
• 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
CIDR
RFC 1517
Applicability statement for implementation of
CIDR
1518
An architecture for IP address allocation with
CIDR
1519
CIDR an address assignment and aggregation
strategy
1520
Method for exchanging routing information
across provider boundaries in a CIDR
environment – there are other RFC numbers
CIDR
/27
New Address Space – 12% of Class C – 30 hosts
/26
24% of Class C – 62 hosts
/25
50% of Class C – 126 hosts
/23
2 Class Cs – 510 hosts
/22
4 Class Cs – 1022 hosts
/21
8 Class Cs – 2046 hosts
/20
16 Class Cs – 4094 hosts
VLSM
• Hierarchical design is the goal
• Physical network design must reflect this
logical hierarchy
• After the physical design is mapped, logical
structure is placed on top of physical design
Rules for VLSM
• A subnet can be used to address hosts, or it can be
used for further subnetting
• The rule of not using all zeros or ones does not
apply to allocation of subsequent subnets
• The routing protocol must carry the subnet mask
in its updates
• Multiple IP addressed to be summarized must
share the same high-order bits
• Routing decisions are made on the entire address
• Prefers the longest bit pattern available
Two Reasons for VLSM
• To make efficient use of available
addressing
• To enforce a good hierarchical design,
allowing summarization and documentation
Advantages of Summarization
• Reduce the size of the routing table
• Reduce network overhead
• Make communication of routing updates more
efficient
• Reduce CPU and memory utilization
• Simplify management
• Maximize use of IP addresses
• Isolate topographical changes from other areas
Private Address Ranges
• 10.0.0.0 to 10.255.255.255
/8
1 Class A
• 172.16.0.0 to 172.31.255.255
/12
16 Class Bs
• 192.168.0.0 to 192.168.255.255
/16
256 Class Cs
IPv6 Topologies
• Public topology – The collection of
providers that provide Internet connectivity
• Site topology – The level local to an
organization that does not provide
connectivity to nodes outside itself
• Interface identifier – The level specific to a
node’s individual interface
IP Helper Address
Service
Time
TACACS
DNS
BOOTP/DHCP Server
BOOTP/DHCP Client
TFTP
NetBIOS Name Service
NetBIOS Datagram Service
Port
37
49
53
67
68
69
137
138
Glossary
Aggregated Route
(aka Route
Summarization)
Consolidation of advertised addresses in a
routing table. Summarizing routes reduces the
number of routes in the table, the update
traffic, and overall overhead
Classful Routing
Protocols
Do not transmit information about prefix
length – RIP and IGRP
Classless Interdomain Means by which the Internet assigns blocks of
Routing (CIDR)
addresses, typically Class C, and summarizes
them using prefix mask
Classless Routing
Protocols
Routing protocols that include the prefix
length with routing updates; routers running
classless routing protocols do not have to
determine the prefix themselves. Classless
routing protocols support VLSM
Glossary
Domain Name
System (DNS)
System used in the Internet for translating
names of network nodes into addresses
Dot Address
Common notation for IP addresses, n.n.n.n
where n (in decimal) is 1 byte of 4-byte
address, aka dotted notation or four-part
dotted notation
Dotted Decimal
Notation
Syntactic representation for a 32 bit integer
that consists of 4 8-bit numbers in base 10
with periods separating them to represent
Internet addresses, aka dotted quad notation
DHCP
Provides mechanism for allocating IP
address dynamically so it can be re-used by
host when needed
Glossary
1st Octet Rule
Layer 3 device identifies the class of IP
address; if protocol is classful address, it is
the only means available to determine the
network portion of an address to which it is
not directly connected
Flooding
Traffic-passing technique used by switches
and bridges to which traffic received on
interface is sent out to all interfaces of that
device except the interface on which the
info was originally received
IANA
Responsible for address allocation on the
Internet
Glossary
Layer 3 Switching
Used in context of VLANS; the mechanism
by which a switch can route between VLANS;
also refers to routers when the routing
decision has been made and the result has
been cached – the subsequent lookup involves
switching on a Layer 3 decision
Logical AND
Mechanism by which a subnet is derived from
an IP host address
Network Address
Translation
Mechanism for reducing the need for globally
unique IP address. NAT allows an
organization with addresses that are not
globally unique to connect to the Internet by
translating those addresses into globally
routable address space
Glossary
Prefix Mask
Identifies the number of bits in the subnet
mask – used in supernetting and router
aggregation
Private Addressing
Means by which organization can address its
network without using a registered address;
saves considerable address space in the
Internet and eases restrictions within the
organization
Routing Table
Stored on router RAM – keeps track of routes
to particular network destinations and metrics
associated with those routes
Subnet Mask
1s are network or subnet bits; 0s are host bits
Glossary
Supernet
Summarization of class addresses given out
by the Internet community. For example, a
group of Class C addresses 200.100.16.0
through 200.100.31.0 could be summarized
into the address 200.100.16.0 with a mask of
255.255.255.0 (/19)
Variable Length
Subnet Mask
Capability to specify a different subnet mask
for the same network number of different
subnets. VLSM can help optimize available
address space. Some protocols do not allow
the use of VLSM (classless routing protocols)
Glossary
Virtual LAN
Logical grouping of devices, identified on
switch ports instead of a physical segment
attached to a router. Devices associated with
the logical network do not have to be
geographically local to one another