文档介绍：EIGRP 路由交換協定
王振生
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EIGRP Overview
Improved version of IGRP
patible with IGRP
Improved convergence
Sends updates like a link state routing protocol
Supports VLSM/CIDR
Supports many layer 3 routed protocols (IP, IPX, AppleTalk etc)
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Comparing EIGRP and IGRP
IGRP
EIGRP
Classless Routing Support
No
Yes
Multi-protocol Support
No
Yes
Length of Metric
24 bits
32 bits
Maximum Hop Count
255
224
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Metric Formula of EIGRP and IGRP
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4 ponents of EIGRP
Neighbor Discovery/Recovery
The process that routers use to dynamically learn of other routers on their directly works
Send hello packet to neighbor
Build neighbor table
Reliable Transport Protocol
Responsible for guaranteed, ordered delivery of EIGRP packets to all neighbors.
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4 ponents of EIGRP
DUAL Finite State pute all routes by metrics
Build routing table
Select the best route(essors) from a set of feasible essors to routing table.
Build topology table which contains essors and feasible essors
Protocol Dependent Modules
Responsible for parsing EIGRP packets and informing DUAL of the new information received
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Feasible essor Route Selection Rules
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EIGRP Features
Hellos sent every 5 secs
Neighbour table
Topology table
DUAL takes information in neighbour & topology table and calculates best routes (‘essors’) and adds them to the Routing Table
‘Feasible essors’ are alternative, backup routes
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Metrics – HOP COUNT
EIGRP also imposes a maximum hop count of 224
IGRP maximum hop count of 255
RIP maximum hop count of 15
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EIGRP Technologies
Hellos multicast every 5 seconds to
Holdtime (route dead) - 3 x hello interval
RTP used as a reliable transport protocol to remain protocol independent
Sequence numbers used on replies/acknowledgements to hellos – unicast NOT multicast
Multicast update packets sent when topology changes
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