Transcript ICSA412 Internetworking Lab

Address Resolution
 The
process of mapping protocol addresses
to hardware addresses
 Only addresses on the same network as the
host are resolved
 Remote addresses are never resolved
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Address Resolution
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Address Resolution
Techniques
 Table
Look up
 Closed-Form Computation
 Message Exchange
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Address Resolution with Table
Lookup
IP ADDRESS
197.15.3.2
197.15.3.3
197.15.3.4
197.15.3.5
HARDWARE ADDRESS
0A:07:4B:12:82:36
0A:08:23:32:4C:44
0A:00:44:24:5D:EF
0A:32:86:23:E3:C1
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Address Resolution with
Closed-Form Computation
 Usually
used where hardware addresses are
configurable
 Usually a simple formula is used to
compute the last part of the hardware
address from the host part of the Protocol
address
 ex. IP addr=
192.168.2.44 -> 01-02-03-04-05-44
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Address Resolution with
Message Exchange
 Distributed
approach
 Host send out a message with the request
and receives back a reply
 Two configurations: server and individual
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Address Resolution Protocol
 Table
lookup is usually used to resolve
WAN addresses
 Closed-form is used on configurable
networks
 Message exchange is used on LANs with
static addressing
 ARP is part of the TCP suite - standard
 Two type messages defined: request & reply
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ARP Message Format
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Sending an ARP Message
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ARP Packet Exchange
192.168.2.1
192.168.2.160
PING 192.168.2.160
ARP Request
ARP Reply
Echo Request
Echo Reply
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