Scaling IP Addresses_NAT

7/28/2019 Scaling IP Addresses_NAT

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CCNA Semester 4: WAN Technologies

Module 1

SCALING IPADDRESSES


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Objectives

Discuss characteristics of NAT and PAT

Explain how to configure NAT and PAT

Describe the characteristics of DHCP Explain how to configure DHCP


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Table of Content

1 Scaling networks with Network Address

Translation and Port Address Translation

2 Dynamic Host Configuration Protocol


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SCALING NETWORKS WITHNAT AND PAT


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Private addressing

10.0.0.0 10.255.255.255

172.16.0.0 172.31.255.255

192.168.0.0 192.168.255.255


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Introducing NAT and PAT

Cisco defines the following NAT terms: Inside local address

Inside global address

Outside local address

Outside global address


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Major NAT and PAT features

Static NAT is designed to allow one-to-onemapping of local and global addresses.

Dynamic NAT is designed to map a privateIP address to a public address. Any IP

address from a pool of public IP addresses

is assigned to a network host.

Port Address Translation (PAT), mapsmultiple private IP addresses to a single

public IP address


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Configuring static NAT

Router(config)# ip nat inside source

static 10.1.1.2 171.69.68.10

Router(config)# interface ethernet 0Router(config-if)# ip nat inside

Router(config)# interface serial 0

Router confi -if # i nat outside

Inside host

10.1.1.2

Outside host

Inside interface

Ip nat inside

Outside interface

Ip nat outside

E0 S0


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Configuring dynamic NAT/PAT

Define private IP addresses range:Router(config)# access-list 1 permit 10.1.1.0 0.0.0.255

Define public IP addresses pool:

Router(config)# ip nat pool cisco 179.9.8.1 179.9.8.14netmask 255.255.255.240

Establish dynamic source translation:Router(config)# ip nat inside source list 1 pool ciscooverload

Specify the inside and outside interface.

InternetE0S0

10.1.1.2

10.1.1.3

10.1.1.1 179.9.8.1


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Verifying PAT configuration

Clear ip nat translation *

Clear ip nat translation inside global-iplocal-ip outside local-ip global-ip

Show ip nat translation

Show ip nat statistics


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Troubleshooting NAT and PAT

configuration1. Based on the configuration, clearly define

what NAT is supposed to achieve. (Da vocu hnh, nh ngha r rng, NAT g c nhim v hon thnh)

2. Verify that correct translations exist in thetranslation table.

3. Verify the translation is occurring by using

show and debug commands.4. Review in detail what is happening to the

packet and verify that routers have the

correct routing information to move the

acket alon with NAT or PAT


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Issues with NAT

NAT conserves the legally registeredaddressing scheme (NAT bo tn h thng t a ch 1

cch hp php)

NAT increases the flexibility ofconnections to the public network (NAT tng tnh

linh hot ca nhng kt ni n mng Public)

Consistency of the internal networkaddressing scheme

NAT increases delay


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Issues with NAT (cont.)

Cisco IOS NAT does not support thefollowing traffic types:

Routing table updates

DNS zone transfers

BOOTP

talk and ntalk protocols

Simple Network Management Protocol(SNMP)


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DHCP


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Introducing DHCP

Dynamic Host Configuration Protocol(DHCP) works in a client/server mode.

DHCP enables DHCP clients on an IP

network to obtain their configurations froma DHCP server.

A DHCP client is included in most modernoperating systems including the variousWindows operating systems, Novell

Netware, Sun Solaris, Linux, and MAC

OS.


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Dynamic addressing: DHCP

MAC: KnownIP: Unknown

DHCP DiscoverUDP Broadcast

DHCP Offer

UDP Broadcast

DHCP server

IP1

IP2

IP3

DHCP Request

DHCP Ack

IP Address

Gateway

IP of servers

And more


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Configuring DHCP Specify DHCP pool:

Router(config)# ip dhcp pool subnet12 Router(dhcp-config)# network 172.16.12.0

255.255.255.0

Router(dhcp-config)# default-router 172.16.12.254

Router(dhcp-config)# dns-server 172.16.1.2 Router(dhcp-config)# netbios-name-server

172.16.1.3

Router(dhcp-config)# domain-name cisco.com

Specify the excluded IP addresses range:

Router(config)# ip dhcp excluded-address start-ip-address

end-ip-address


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DHCP relay

E0: 192.168.1.1/24

Ip helper-address 192.168.2.254

E1: 192.168.2.1/24

IP???

A

server: 192.168.2.254

SRC MAC: MAC A

DST MAC:FFFF.FFFF.FFFF

IP SRC: ?

IP DST: 255.255.255.255

UD

P67

CIADDR: ? GIADDR: ?

MASK: ? CHADDR:MAC A

SRC MAC: E1

DST MAC: MAC

SERVER

IP SRC: 192.168.2.1

IP DST: 192.168.2.254

UD

P

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CIADDR: ? GIADDR:

192.168.1.1

MASK: ? CHADDR: MAC A


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DHCP relay (cont.)

E0: 192.168.1.1/24

Ip helper-address 192.168.2.254

E1: 192.168.2.1/24

IP???

A

server: 192.168.2.254

SRC MAC: E0

DST MAC: MACA

IP SRC:

192.168.2.254IP DST: 192.168.1.10

UD

P68

CIADDR: 192.168.1.10 GIADDR:

192.168.1.1MASK: 255.255.255.0 CHADDR: MAC A

SRC MAC:MAC

SERV

DST MAC: E1

IP SRC:

192.168.2.254

IP DST: 192.168.1.10

UD

P

68

CIADDR:192.168.1.10 GIADDR:

192.168.1.1

MASK: 255.255.255.0 CHADDR: MAC A


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Summary

Private addresses are for private, internal use andshould never be routed by a public Internet router.

NAT alters the IP header of a packet so that thedestination address, the source address, or both

addresses are replaced with different addresses. PAT uses unique source port numbers on the inside

global IP address to distinguish between translations.

NAT and PAT may be configured for static translation,

dynamic translation, and overloading DHCP works in a client/server mode, enabling clients

to obtain IP configurations from a DHCP server


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Q&A


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Scaling IP Addresses_NAT

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