Transcript Document

Ch.2 – Advanced IP Address
Management
CCNP 1 version 3.0 – Advanced Routing
Rick Graziani
Cabrillo College
1
Note to instructors
• If you have downloaded this presentation from the Cisco Networking
Academy Community FTP Center, this may not be my latest version of
this PowerPoint.
• For the latest PowerPoints for all my CCNA, CCNP, and Wireless
classes, please go to my web site:
http://www.cabrillo.cc.ca.us/~rgraziani/
• The username is cisco and the password is perlman for all of
my materials.
• If you have any questions on any of my materials or the curriculum,
please feel free to email me at [email protected] (I really don’t
mind helping.) Also, if you run across any typos or errors in my
presentations, please let me know.
• I will add “(Updated – date)” next to each presentation on my web site
that has been updated since these have been uploaded to the FTP
center.
Thanks! Rick
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2
Objectives
This module explores the evolution and extension of IPv4,
including the key scalability features that engineers have
added to it over the years:
• Subnetting
• Classless interdomain routing (CIDR)
• Variable length subnet masking (VLSM)
• Route summarization
Finally, this module examines advanced IP implementation
techniques such as the following:
• IP unnumbered
• Dynamic Host Configuration Protocol (DHCP)
• Helper addresses
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3
A few notes…
•
•
The following slides are NOT from the online curriculum.
However, they do cover the same topics, just with different
examples.
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4
IPv4 Address Classes
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5
IPv4 Address Classes
• No medium size host networks
• In the early days of the Internet, IP addresses were allocated to
organizations based on request rather than actual need.
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IPv4 Address Classes
Class D Addresses
• A Class D address begins with binary 1110 in the first octet.
• First octet range 224 to 239.
• Class D address can be used to represent a group of hosts called a
host group, or multicast group.
Class E Addresses
First octet of an IP address begins with 1111
• Class E addresses are reserved for experimental purposes and should
not be used for addressing hosts or multicast groups.
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IP addressing crisis
•
•
Address Depletion
Internet Routing Table Explosion
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IPv4 Addressing
Subnet Mask
• One 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.
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Subnet Example
Given the Class B address 190.52.0.0
Class B
Using /24
subnet...
Network Network
Network Network
Host
Subnet
Host
Host
Internet routers still “see” this net as 190.52.0.0
190.52.1.2
190.52.2.2
190.52.3.2
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But internal routers think all
these addresses are on different
networks, called subnetworks
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Subnet Example
Network Network
Subnet
Host
Using the 3rd octet, 190.52.0.0 was divided into:
190.52.1.0
190.52.5.0
190.52.9.0
190.52.13.0
190.52.17.0
190.52.2.0
190.52.6.0
190.52.10.0
190.52.14.0
190.52.18.0
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190.52.3.0
190.52.7.0
190.52.11.0
190.52.15.0
190.52.19.0
190.52.4.0
190.52.8.0
190.52.12.0
190.52.16.0
and so on ...
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All Zeros and All Ones Subnets
Using the All Ones Subnet
• There is no command to enable or disable the use of the all-ones subnet, it is
enabled by default.
Router(config)#ip subnet-zero
• The use of the all-ones subnet has always been explicitly allowed and the use
of subnet zero is explicitly allowed since Cisco IOS version 12.0.
RFC 1878 states, "This practice (of excluding all-zeros and all-ones subnets) is
obsolete! Modern software will be able to utilize all definable networks."
Today, the use of subnet zero and the all-ones subnet is generally accepted
and most vendors support their use, though, on certain networks,
particularly the ones using legacy software, the use of subnet zero and the
all-ones subnet can lead to problems.
CCO: Subnet Zero and the All-Ones Subnet
http://www.cisco.com/en/US/tech/tk648/tk361/technologies_tech_note09186a
0080093f18.shtml
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Need a Subnet Review?
•
If you need a Review of Subnets, please review the
following links on my web site:
– Subnet Review (PowerPoint)
– Subnets Explained (Word Doc)
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13
Long Term Solution: IPv6 (coming)
•
•
•
•
•
•
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.
IPv6 has been slow to arrive
IPv4 revitalized by new features, making IPv6 a luxury, and not
a desperately needed fix
IPv6 requires new software; IT staffs must be retrained
IPv6 will most likely coexist with IPv4 for years to come.
Some experts believe IPv4 will remain for more than 10 years.
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Short Term Solutions: IPv4 Enhancements
•
•
•
•
CIDR (Classless Inter-Domain Routing) – RFCs 1517,
1518, 1519, 1520
VLSM (Variable Length Subnet Mask) – RFC 1009
Private Addressing - RFC 1918
NAT/PAT (Network Address Translation / Port Address
Translation) – RFC
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CIDR (Classless Inter-Domain Routing)
• By 1992, members of the IETF were having serious concerns about the
•
•
•
•
•
exponential growth of the Internet and the scalability of Internet routing
tables.
The IETF was also concerned with the eventual exhaustion of 32-bit
IPv4 address space.
Projections were that this problem would reach its critical state by 1994
or 1995.
IETF’s response was the concept of Supernetting or CIDR, “cider”.
To CIDR-compliant routers, address class is meaningless.
– The network portion of the address is determined by the network
subnet mask, network-prefix or prefix-length (/8, /19, etc.)
– The network address is NOT determined by the first octet (first two
bits), 200.10.0.0/16 or 15.10.160.0/19
CIDR helped reduced the Internet routing table explosion with
supernetting and reallocation of IPv4 address space.
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Active BGP entries
Report last updated at Thu, 16 Jan 2003
http://bgp.potaroo.net/
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CIDR (Classless Inter-Domain Routing)
• First deployed in 1994, CIDR dramatically improves IPv4’s scalability
•
and efficiency by providing the following:
– Eliminates traditional Class A, B, C addresses allowing for more
efficient allocation of IPv4 address space.
– Supporting route aggregation (summarization), also known as
supernetting, where thousands of routes could be represented by a
single route in the routing table.
• Route aggregation also helps prevent route flapping on Internet
routers using BGP. Flapping routes can be a serious concern
with Internet core routers.
CIDR allows routers to aggregate, or summarize, routing information
and thus shrink the size of their routing tables.
– Just one address and mask combination can represent the routes to
multiple networks.
– Used by IGP routers within an AS and EGP routers between AS.
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Without CIDR, a
router must
maintain
individual
routing table
entries for these
class B
networks.
With CIDR, a
router can
summarize
these routes
into eight
networks by
using a 13-bit
prefix:
172.24.0.0 /13
Steps:
1. Count the number of left-most matching bits, /13
2. Add all zeros after the last matching bit:
172.24.0.0 = 10101100 00011000 00000000 00000000
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CIDR (Classless Inter-Domain Routing)
• By using a prefix address to summarizes routes, administrators can
•
•
•
•
keep routing table entries manageable, which means the following
– More efficient routing
– A reduced number of CPU cycles when recalculating a routing
table, or when sorting through the routing table entries to find a
match
– Reduced router memory requirements
Route summarization is also known as:
– Route aggregation
– Supernetting
Supernetting is essentially the inverse of subnetting.
CIDR moves the responsibility of allocation addresses away from a
centralized authority (InterNIC).
Instead, ISPs can be assigned blocks of address space, which they
can then parcel out to customers.
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ISP/NAP Hierarchy - “The Internet: Still hierarchical after all
these years.” Jeff Doyle (Tries to be anyways!)
NAP (Network Access Point)
Network
Service
Provider
Regional
Service
Provider
ISP
Subscribers
ISP
Subscribers
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ISP
Subscribers
Network
Service
Provider
Regional
Service
Provider
Regional
Service
Provider
ISP
ISP
Subscribers
Subscribers
Regional
Service
Provider
ISP
Subscribers
ISP
Subscribers
ISP
Subscribers
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Supernetting Example
• Company XYZ needs to address 400 hosts.
• Its ISP gives them two contiguous Class C addresses:
•
•
– 207.21.54.0/24
– 207.21.55.0/24
Company XYZ can use a prefix of 207.21.54.0 /23 to supernet
these two contiguous networks. (Yielding 510 hosts)
207.21.54.0 /23
– 207.21.54.0/24
– 207.21.55.0/24
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23 bits in common
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Supernetting Example
•
With the ISP acting as the addressing authority for a CIDR block of
addresses, the ISP’s customer networks, which include XYZ, can be
advertised among Internet routers as a single supernet.
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CIDR and the Provider
Another example of route aggregation.
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CIDR and the provider
200.199.48.0/25
200.199.56.0/23
Summarization from
the customer
networks to their
provider.
Even Better:
200.199.48.32/27 11001000 11000111 00110000 0 0100000
200.199.48.64/27 11001000 11000111 00110000 0 1000000
200.199.48.96/27 11001000 11000111 00110000 0 1100000
200.199.48.0/25 11001000 11000111 00110000 0 0000000
(As long as there are no other routes elsewhere within this range, well…)
200.199.56.0/24
200.199.57.0/24
200.199.56.0/23
11001000 11000111 0011100 0 00000000
11001000 11000111 0011100 1 00000000
11001000 11000111 0011100 0 00000000
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CIDR and the provider
200.199.48.0/25
200.199.56.0/23
Further summarization
happens with the next
upstream provider.
200.199.48.0/25
200.199.49.0/25
200.199.56.0/23
11001000 11000111 0011 0000 00000000
11001000 11000111 0011 0001 00000000
11001000 11000111 0011 1000 00000000
200.199.48.0/20
11001000 11000111 0011 0000 00000000
20 bits in common
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CIDR Restrictions
• Dynamic routing protocols must send network address and mask
•
•
(prefix-length) information in their routing updates.
In other words, CIDR requires classless routing protocols for dynamic
routing.
However, you can still configure summarized static routes, after all, that
is what a 0.0.0.0/0 route is.
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Summarized and Specific Routes: Longest-bit Match
(more later)
Merida
Summarized Update
Specific Route Update
172.16.0.0/16
172.16.1.0/24
172.16.5.0/24
172.16.5.0/24
Quito
Cartago
172.16.2.0/24 172.16.10.0/24
• Merida receives a summarized /16 update from Quito and a more
•
•
•
specific /24 update from Cartago.
Merida will include both routes in the routing table.
Merida will forward all packets matching at least the first 24 bits of
172.16.5.0 to Cartago (172/16/5/0/24), longest-bit match.
Merida will forward all other packets matching at least the first 16 bits
to Quito (172.16.0.0/16).
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28
Short Term Solutions: IPv4 Enhancements
•
•
•
•
CIDR (Classless Inter-Domain Routing) – RFCs 1517,
1518, 1519, 1520
VLSM (Variable Length Subnet Mask) – RFC 1009
Private Addressing - RFC 1918
NAT/PAT (Network Address Translation / Port Address
Translation) – RFC
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VLSM (Variable Length Subnet Mask)
•
•
•
Limitation of using only a single subnet mask across a
given network-prefix (network address, the number of
bits in the mask) was that an organization is locked into a
fixed-number of of fixed-sized subnets.
1987, RFC 1009 specified how a subnetted network could
use more than one subnet mask.
VLSM = Subnetting a Subnet
– “If you know how to subnet, you can do VLSM!”
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VLSM – Simple Example
•
•
1st octet
2nd octet
3rd octet
4th octet
10.0.0.0/8
10
Host
Host
Host
10.0.0.0/16
10
Subnet
Host
Host
10.0.0.0/16
10
0
Host
Host
10.1.0.0/16
10.2.0.0/16
10.n.0.0/16
10.255.0.0/16
10
10
10
10
1
2
…
255
Host
Host
Host
Host
Host
Host
Host
Host
Subnetting a /8 subnet using a /16 mask gives us 256 subnets with
65,536 hosts per subnet.
Let’s take the 10.2.0.0/16 subnet and subnet it further…
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VLSM – Simple Example
Network
Subnet
Host
Host
10.2.0.0/16
10
2
Host
Host
10.2.0.0/24
10
2
Subnet
Host
10.2.0.0/24
10.2.1.0/24
10
10
2
2
0
1
Host
Host
10.2.n.0/24
10.2.255.0/24
10
10
2
2
…
255
Host
Host
•
•
Note: 10.2.0.0/16 is now a summary of all of the 10.2.0.0/24
subnets.
Summarization coming soon!
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32
VLSM – Simple Example
10.0.0.0/8
Subnet
10.0.0.0/16
10.1.0.0/16
“subnetted using /16”
1st host
Last host
Broadcast
10.0.0.1
10.0.255.254
10.0.255.255
10.1.0.1
10.1.255.254
10.1.255.255
10.2.0.0/16 “sub-subnetted using /24”
–Subnet
1st host
Last host
Broadcast
–10.2.0.0/24
10.2.0.1
10.2.0.254
10.2.0.255
–10.2.1.0/24
10.2.1.1
10.2.1.254
10.2.1.255
–10.2.2.0/24
10.2.2.1
10.2.2.254
10.2.2.255
– Etc.
–10.2.255.0/24 10.2.255.1 10.2.255.254 10.2.255.255
10.3.0.0/16
Etc.
10.255.0.0/16
10.3.0.1
10.3.255.254
10.0.255.255
10.255.0.1 10.255.255.254 10.255.255.255
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33
VLSM – Simple Example
Subnets
10.0.0.0/16
10.1.0.0/16
10.2.0.0/16
10.2.0.0/24
10.2.1.0/24
10.2.2.0/24
Etc.
10.2.255.0/24
10.3.0.0/16
Etc.
10.255.0.0/16
•
•
•
An example of VLSM, NOT of good network design.
10.1.0.0/16
10.2.0.0/24
10.2.1.0/24
10.7.0.0/16
10.3.0.0/16
10.2.6.0/24
10.4.0.0/16
10.2.3.0/24
10.2.8.0/24
10.5.0.0/16 10.8.0.0/16
10.2.5.0/24
10.6.0.0/16
10.2.4.0/24
Your network can now have 255 /16 subnets with 65,534 hosts each AND
256 /24 subnets with 254 hosts each.
All you need to make it work is a classless routing protocol that passes
the subnet mask with the network address in the routing updates.
Classless routing protocols: RIPv2, EIGRP, OSPF, IS-IS, BGPv4 (coming)
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34
Another VLSM Example using /30 subnets
207.21.24.0/24 network subnetted into eight /27 (255.255.255.224)
subnets
207.21.24.192/27 subnet, subnetted into eight /30
(255.255.255.252) subnets
•
•
This network has seven /27 subnets with 30 hosts each
AND eight /30 subnets with 2 hosts each.
/30 subnets are very useful for serial networks.
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35
207.21.24.192/27
0
1
2
3
4
5
6
7
207.21.24.192/30
207.21.24.196/30
207.21.24.200/30
207.21.24.204/30
207.21.24.208/30
207.21.24.212/30
207.21.24.216/30
207.21.24.220/30
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207.21.24. 11000000
/30
207.21.24. 110 00000
207.21.24. 110 00100
207.21.24. 110 01000
207.21.24. 110 01100
207.21.24. 110 10000
207.21.24. 110 10100
207.21.24. 110 11000
207.21.24. 110 11100
Hosts Bcast
01 10 11
01 10 11
01 10 11
01 10 11
01 10 11
01 10 11
01 10 11
01 10 11
2 Hosts
.193 & .194
.197 & .198
.201 & .202
.205 & .206
.209 & .210
.213 & .214
.217 & .218
.221 & .222
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207.21.24.192/30
207.21.24.204/30
207.21.24.216/30
207.21.24.96/27
207.21.24.128/27
207.21.24.64/27
207.21.24.196/30
207.21.24.160/27
•
•
207.21.24.208/30
207.21.24.200/30
207.21.24.224/27
207.21.24.32/27
207.21.24.212/30
207.21.24.0/27
This network has seven /27 subnets with 30 hosts each AND seven
/30 subnets with 2 hosts each (one left over).
/30 subnets with 2 hosts per subnet do not waste host addresses on
serial networks .
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37
VLSM and the Routing Table (more later)
Displays one subnet mask for all child routes.
Classful mask is assumed for the parent route.
Routing Table without VLSM
RouterX#show ip route
207.21.24.0/27 is subnetted,
C
207.21.24.192 is directly
C
207.21.24.196 is directly
C
207.21.24.200 is directly
C
207.21.24.204 is directly
4 subnets
connected,
connected,
connected,
connected,
Serial0
Serial1
Serial2
FastEthernet0
Each child routes displays its own subnet mask.
Classful mask is included for the parent route.
Routing Table with VLSM
RouterX#show ip route
207.21.24.0/24 is variably subnetted, 4 subnets, 2 masks
C
207.21.24.192 /30 is directly connected, Serial0
C
207.21.24.196 /30 is directly connected, Serial1
C
207.21.24.200 /30 is directly connected, Serial2
C
207.21.24.96 /27 is directly connected, FastEthernet0
• Parent Route shows classful mask instead of subnet mask of the child
routes.
• Each Child Routes includes its subnet mask.
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Final Notes on VLSM
•
Whenever possible it is best to group contiguous routes
together so they can be summarized (aggregated) by
upstream routers. (coming soon!)
– Even if not all of the contiguous routes are
together, routing tables use the longest-bit
match which allows the router to choose the
more specific route over a summarized route.
– Coming soon!
•
•
You can keep on sub-subnetting as many times and as
“deep” as you want to go.
You can have various sizes of subnets with VLSM.
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39
Route flapping
•
Route flapping occurs when a router interface alternates rapidly between the
up and down states.
• Route flapping, and it can cripple a router with excessive updates and
recalculations.
• However, the summarization configuration prevents the RTC route flapping
from affecting any other routers.
• The loss of one network does not invalidate the route to the supernet.
• While RTC may be kept busy dealing with its own route flap, RTZ, and all
upstream routers, are unaware of any downstream problem.
• Summarization effectively insulates the other routers from the problem of route
Rick flapping.
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40
Short Term Solutions: IPv4 Enhancements
•
•
•
•
CIDR (Classless Inter-Domain Routing) – RFCs 1517,
1518, 1519, 1520
VLSM (Variable Length Subnet Mask) – RFC 1009
Private Addressing - RFC 1918
NAT/PAT (Network Address Translation / Port Address
Translation) – RFC
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41
Private IP addresses (RFC 1918)
If addressing any of the following, these private addresses can be used instead of globally
unique addresses:
• A non-public intranet
• A test lab
• A home network
Global addresses must be obtained from a provider or a registry at some expense.
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42
Discontiguous subnets
• “Mixing private addresses with globally unique addresses can create
•
•
discontiguous subnets.” – Not the main cause however…
Discontiguous subnets, are subnets from the same major network that
are separated by a completely different major network or subnet.
Question: If a classful routing protocol like RIPv1 or IGRP is being used, what
do the routing updates look like between Site A router and Site B router?
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43
Discontiguous subnets
•
•
•
•
Classful routing protocols, notably RIPv1 and IGRP, can’t support
discontiguous subnets, because the subnet mask is not included in routing
updates.
RIPv1 and IGRP automatically summarize on classful boundaries.
Site A and Site B are all sending each other the classful address of
207.21.24.0/24.
A classless routing protocol (RIPv2, EIGRP, OSPF) would be needed:
– to not summarize the classful network address and
– to include the subnet mask in the routing updates.
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44
Discontiguous subnets
•
•
RIPv2 and EIGRP automatically summarize on classful boundaries.
When using RIPv2 and EIGRP, to disable automatic summarization (on both
routers):
Router(config-router)#no auto-summary
•
•
SiteB now receives 207.21.24.0/27
SiteB now receives 207.21.24.32/27
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45
Short Term Solutions: IPv4 Enhancements
•
•
•
•
CIDR (Classless Inter-Domain Routing) – RFCs 1517,
1518, 1519, 1520
VLSM (Variable Length Subnet Mask) – RFC 1009
Private Addressing - RFC 1918
NAT/PAT (Network Address Translation / Port Address
Translation) – RFC
Rick Graziani [email protected]
46
Network Address Translation (NAT)
NAT: Network Address Translatation
• NAT, as defined by RFC 1631, is the process of swapping one address
for another in the IP packet header.
• In practice, NAT is used to allow hosts that are privately addressed to
access the Internet.
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47
Network Address Translation (NAT)
•
•
TCP Source Port 1026
2.2.2.2 TCP Source Port 1923
TCP Source Port 1026
2.2.2.2 TCP Source Port 1924
NAT translations can occur dynamically or statically.
The most powerful feature of NAT routers is their capability to use port
address translation (PAT), which allows multiple inside addresses to map to
the same global address.
• This is sometimes called a many-to-one NAT.
• With PAT, or address overloading, literally hundreds of privately addressed
nodes can access the Internet using only one global address.
• The NAT router keeps track of the different conversations by mapping TCP and
UDP port numbers.
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48
Using IP unnumbered
There are certain drawbacks that come with using IP unnumbered:
• The use of ping cannot determine whether the interface is up because the interface has
no IP address.
• A network IOS image cannot boot over an unnumbered serial interface.
• IP security options cannot be supported on an unnumbered interface.
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49
DHCP
•
•
•
•
DHCP overview
DHCP operation
Configuring IOS DHCP server
Easy IP
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50
DHCP overview
• Administrators set up DHCP servers to assign addresses from
•
•
predefined pools. DHCP servers can also offer other information:
– DNS server addresses
– WINS server addresses
– Domain names
Most DHCP servers also allow the ability to define specifically what
client MAC addresses can be serviced and to automatically assign the
same number to a particular host each time.
Note: BootP was originally defined in RFC 951 in 1985. It is the
predecessor of DHCP, and it shares some operational characteristics.
Both protocols use UDP ports 67 and 68, which are well known as
BootP ports because BootP came before DHCP.
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51
DHCP operation
•
•
•
•
•
•
The client sends a DHCPREQUEST broadcast to all nodes.
If the client finds the offer agreeable, it will send another broadcast.
This broadcast is a DHCPREQUEST, specifically requesting those particular
IP parameters.
Why does the client broadcast the request instead of unicasting it to the
server?
A broadcast is used because the very first message, the DHCPDISCOVER,
may have reached more than one DHCP server.
After all, it was a broadcast. If more than one server makes an offer, the
broadcasted DHCPREQUEST lets the servers know which offer was
accepted, which is usually the first offer received.
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Configuring IOS DHCP server
Basic
More
options…
• Note: The network statement enables DHCP on any router
interfaces belonging to that network.
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Configuring IOS DHCP server
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Easy IP
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Using helper addresses
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Configuring IP helper addresses
By default, the ip helper-address command forwards the eight UDPs services.
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Configuring IP helper addresses
Broadcast
Unicast
To configure RTA e0, the interface that receives the Host A broadcasts, to
relay DHCP broadcasts as a unicast to the DHCP server, use the
following commands:
RTA(config)#interface e0
RTA(config-if)#ip helper-address 172.24.1.9
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Configuring IP helper addresses
Broadcast
Unicast
Helper address configuration that relays broadcasts to all servers on the
segment.
RTA(config)#interface e0
RTA(config-if)#ip helper-address 172.24.1.255
But will RTA forward the broadcast?
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Directed Broadcast
•
•
•
•
Notice that the RTA interface e3, which connects to the server farm, is not
configured with helper addresses.
However, the output shows that for this interface, directed broadcast
forwarding is disabled.
This means that the router will not convert the logical broadcast 172.24.1.255
into a physical broadcast with a Layer 2 address of FF-FF-FF-FF-FF-FF.
To allow all the nodes in the server farm to receive the broadcasts at Layer 2,
e3 will need to be configured to forward directed broadcasts with the following
command:
RTA(config)#interface e3
RTA(config-if)#ip
directed-broadcast
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Configuring IP helper addresses
L3 Broadcast
L2 Broadcast
Helper address configuration that relays broadcasts to all servers on the
segment.
RTA(config)#interface e0
RTA(config-if)#ip helper-address 172.24.1.255
RTA(config)#interface e3
RTA(config-if)#ip directed-broadcast
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IP address issues solutions
This module has shown that IPv4 addressing faces two major issues:
• The depletion of addresses, particularly the key medium-sized space
• The pervasive growth of Internet routing tables
In 1994, the Internet Engineering Task Force (IETF) proposed IPv6 in RFC 1752
and a number of working groups were formed in response. IPv6 covers issues
such as the following:
• Address depletion
• Quality of service
• Address autoconfiguration
• Authentication
• Security
It will not be easy for organizations deeply invested in the IPv4 scheme to migrate
to a totally new architecture. As long as IPv4, with its recent extensions and
CIDR enabled hierarchy, remains viable, administrators will shy away from
adopting IPv6. A new IP protocol requires new software, new hardware, and
new methods of administration. It is likely that IPv4 and IPv6 will coexist, even
within an autonomous system, for years to come.
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IPv6
Three general types of addresses exist:
• 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 that typically belong 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 that typically belong to different
nodes. A packet sent to a multicast address is delivered to all interfaces in the
multicast group.
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IPv6
• To write 128-bit addresses so that they are readable to human eyes,
•
the IPv6 architects abandoned dotted decimal notation in favor of a
hexadecimal format.
Therefore, IPv6 is written as 32 hex digits, with colons separating the
values of the eight 16-bit pieces of the address.
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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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Summary
This module described how all of the following could enable
more efficient use of IP addresses:
• Subnet masks
• VLSMs
• Private addressing
• Network address translation (NAT)
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