CCNP RoutingSemester 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 All OSPF routers

• 224.0.0.6 All OSPF designated routers (DRs)

• 224.0.0.9 All RIP2 routers

• 224.0.0.10 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

CIDRRFC 1517

1518

1519

1520

Applicability statement for implementation of CIDR

An architecture for IP address allocation with CIDR

CIDR an address assignment and aggregation strategy

Method for exchanging routing information across provider boundaries in a CIDR environment – there are other RFC numbers

CIDR/27

/26

/25

/23

/22

/21

/20

New Address Space – 12% of Class C – 30 hosts

24% of Class C – 62 hosts

50% of Class C – 126 hosts

2 Class Cs – 510 hosts

4 Class Cs – 1022 hosts

8 Class Cs – 2046 hosts

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 PortTime 37TACACS 49DNS 53BOOTP/DHCP Server 67BOOTP/DHCP Client 68TFTP 69NetBIOS Name Service 137NetBIOS Datagram Service 138

GlossaryAggregated Route(aka Route Summarization)

Classful Routing Protocols

Classless Interdomain Routing (CIDR)

Classless Routing Protocols

Consolidation of advertised addresses in a routing table. Summarizing routes reduces the number of routes in the table, the update traffic, and overall overhead

Do not transmit information about prefix length – RIP and IGRP

Means by which the Internet assigns blocks of addresses, typically Class C, and summarizes them using prefix mask

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

GlossaryDomain Name System (DNS)

Dot Address

Dotted Decimal Notation

DHCP

System used in the Internet for translating names of network nodes into addresses

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

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

Provides mechanism for allocating IP address dynamically so it can be re-used by host when needed

Glossary1st Octet Rule

Flooding

IANA

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

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

Responsible for address allocation on the Internet

GlossaryLayer 3 Switching

Logical AND

Network Address Translation

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

Mechanism by which a subnet is derived from an IP host address

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

GlossaryPrefix Mask

Private Addressing

Routing Table

Subnet Mask

Identifies the number of bits in the subnet mask – used in supernetting and router aggregation

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

Stored on router RAM – keeps track of routes to particular network destinations and metrics associated with those routes

1s are network or subnet bits; 0s are host bits

GlossarySupernet

Variable Length Subnet Mask

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)

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)

GlossaryVirtual 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