eigrp fundamentals
TRANSCRIPT
11
Semester 5Semester 5
Chapter 6EIGRP
22
ObjectiveObjectiveUpon completion of this chapter, you will
be able to perform the following tasks:►Describe EIGRP features and operation►Explain how EIGRP discovers, chooses, and
maintains routes►Explain how EIGRP supports the use of VLSM
and route summarization►Explain how EIGRP operates in an NBMA
environment►Describe how EIGRP supports large networks►Configure and Verify EIGRP
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TopicTopic
1. EIGRP Fundamentals2. EIGRP Features3. EIGRP Components4. EIGRP Operation5. Configuring EIGRP6. Monitoring EIGRP7. Summary/Question and Answer
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EIGRP FundamentalEIGRP Fundamental
1. EIGRP Overview2. EIGRP and IGRP compatibility 3. EIGRP design 4. EIGRP support for Novell IPX and
AppleTalk 5. EIGRP terminology
55
EIGRP OverviewEIGRP OverviewCisco released EIGRP in 1994 as a
scalable, improved version routing protocol to replace IGRP.
EIGRP supports:►Rapid convergence►Reduced bandwidth usage►Multiple network-layer protocols
supported►Easy to configure….
66
EIGRP and IGRP compatibilityEIGRP and IGRP compatibility EIGRP uses a different metric calculation
►EIGRP scales IGRP's metric by a factor of 256. ►EIGRP uses a metric that is 32 bits long (IGRP 24-bit )
By multiplying or dividing by 256, EIGRP can easily exchange
information with IGRP.
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EIGRP and IGRP compatibilityEIGRP and IGRP compatibility
Different hop-count limitation►EIGRP also imposes a maximum hop limit of
224 < IGRP's generous 255Similar with IGRP►Getting dissimilar routing protocols (RIP,
OSPF..) need to redistribute or add on configuration.
►Sharing, or redistribution, is automatic between IGRP and EIGRP if same AS number.
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EIGRP design EIGRP design EIGRP acts like a link-state protocol when
updating neighbors and maintaining routing information.
EIGRP's advantages over simple distance-vector protocols :►Rapid convergence (because use Diffusing Update
Algorithm - DUAL)►Efficient use of bandwidth
Partial, bounded (incremental) updatesMinimal consumption of bandwidth when the network is
stable with small hello packets►Support for VLSM and CIDR►Multiple network-layer support and Independence
from routed protocols
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EIGRP with IPXEIGRP with IPX
Redistribute IPX RIP and SAP information to improve overall performance► Take over for these two protocols. ► Router will receive routing and service updates and then update other
routers only when changes in occur: Routing updates occur as they would in any EIGRP network - using partial
updates. EIGRP sends SAP updates incrementally on all serial interfaces by default
► Advanced Metric, Hop from RIP, NLSP and SAP► Cisco IOS > 11.1 EIGRP can redistribute NLSP
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EIGRP with AppleTalkEIGRP with AppleTalkEIGRP can also take over for AppleTalk's
Routing Table Maintenance Protocol (RTMP - distance-vector routing protocol).
EIGRP redistributes AppleTalk routing information using event-driven updates.
Configurable composite metric to determine the best route to an AppleTalk network.
Remember:►AppleTalk clients expect RTMP information from local
routers.►EIGRP for AppleTalk should be run only on a
clientless network, such as a WAN link.
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EIGRP terminologyEIGRP terminologyKeep route and topology information readily in RAM
react quickly to changes. Neighbor table
► The lists adjacent routers, each protocol each table Topology Table
► Route entries for all destinations, each protocol each table Routing Table
► The best route from Topology table, each protocol each table Successor
► Primary route to reach destination► Kept in routing table► Multiple successors for a destination can be retained in the routing table
Feasible successor (FS)► Backup route► Kept in Topology Table► Multiple FS for a destination can be retained in the Topology table
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EIGRP FeaturesEIGRP Features
1. EIGRP technologies 2. Neighbor discovery and recovery 3. Reliable transport protocol 4. DUAL finite-state machine 5. Protocol-dependent modules
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EIGRP technologiesEIGRP technologies
Many new technologies are improvement in operating efficiency, rapidity of convergence, or functionality relative another Routing protocol
Four categories: 1.Neighbor discovery and recovery 2.Reliable Transport Protocol 3.DUAL finite-state machine 4.Protocol-specific modules
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Neighbor discovery and recoveryNeighbor discovery and recovery EIGRP routers actively establish
relationships with their neighbors same way that OSPF routers do.
EIGRP routers establish adjacencies with neighbor routers by using small hello packets (default every 5s or 60s).
By forming adjacencies, EIGRP routers do:►Dynamically learn of new routes that
join their network► Identify routers that become either
unreachable or inoperable►Rediscover routers that had
previously been unreachable
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I am router A, who is on the link?Hello
A B
1
Initial Route DiscoveryInitial Route Discovery
Here is my complete routing information. Update2
Thanks for the information!
Ack3Topology
Table
4
Here is my complete route information.Update5
Converged
Thanks for the information! 6
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Reliable transport protocol (RTP)Reliable transport protocol (RTP)
RTP,EIGRP own protocol, is a transport-layer protocol that can guarantee ordered delivery of EIGRP packets to all neighbors.
EIGRP can call on RTP to provide reliable or unreliable service as the situation warrants.
Reliable delivery of other routing information can actually speed convergence because EIGRP routers are not waiting for a timer to expire before they retransmit.
EIGRP can multicast and unicast to different peers simultaneously, allowing for maximum efficiency.
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Reliable transport protocol (RTP)Reliable transport protocol (RTP)
EIGRP reliable packets are packets that requires explicit acknowledgement:►Update►Query►Reply
EIGRP unreliable packets are packets that do not require explicit acknowledgement:►Hello►Ack
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Reliable transport protocol (RTP)Reliable transport protocol (RTP)
The router keeps a neighbor list and a retransmission list for every neighbor
Each reliable packet (update, query, reply) will be retransmitted when packet is not acknowledged
Neighbor relationship is reset when retry limit (limit = 16) for reliable packets is reached This information is required to allow EIGRP to maintain a loop-free topology at all times.
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Reliable transport protocol (RTP)Reliable transport protocol (RTP)
EIGRP transport has window size of one (stop and wait mechanism)►Every single reliable packet needs to be
acknowledged before the next sequenced packet can be sent
►If one or more peers are slow in acknowledging, all other peers suffer from this
Solution: The non acknowledged multicast packet will be retransmitted as a unicast to the slow neighbor
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DUAL finite-state machine (DFS)DUAL finite-state machine (DFS)
Diffusing Update Algorithm (DUAL) EIGRP's route-calculation engine.
DFS:►Tracks all routes advertised by neighbors.►Lowest-cost paths are inserted by the DUAL
protocol into the routing table.►Select loop-free path using a successor and
remember any feasible successors.If successor lost: Use feasible successorIf no feasible successor: Query neighbors and
recomputed new successor
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DUAL ExampleDUAL Example
E EIGRP FD AD Topology (a) 3 (fd)
via D 3 2 (Successor)via C 4 3
D EIGRP FD AD Topology(a) 2 (fd)
via B 2 1 (Successor)via C 5 3
C EIGRP FD AD Topology(a) 3 (fd)
via B 3 1 (Successor)via D 4 2 (fs)via E 4 3
(1)
(1)
(1)
(1)
(2)(2)
(a)
A
E
D
C
B
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D EIGRP FD AD Topology(a) 2 (fd)
via B 2 1 (Successor)via C 5 3
DUAL ExampleDUAL Example
E EIGRP FD AD Topology (a) 3 (fd)
via D 3 2 (Successor)via C 4 3
C EIGRP FD AD Topology(a) 3 (fd)
via B 3 1 (Successor)via D 4 2 (fs)via E 4 3
(1)
(1)
(1)
(1)
(2)(2)
(a)
A
E
D
C
B XX
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DUAL ExampleDUAL Example
Q Q(1)
(1)
(1)
(2)(2)
(a)
A
E
D
C
B
E EIGRP FD AD Topology (a) 3 (fd)
via D 3 2 (Successor)via C 4 3
D EIGRP FD AD Topology(a) **ACTIVE** -1 (fd)
via E (q)via C 5 3 (q)
C EIGRP FD AD Topology(a) 3 (fd)
via B 3 1 (Successor)via Dvia E 4 3
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DUAL ExampleDUAL Example
R
Q
(1)
(1)
(1)
(2)(2)
(a)
A
E
D
C
B
E EIGRP FD AD Topology (a) **ACTIVE** -1 (fd)
via D via C 4 3 (q)
D EIGRP FD AD Topology(a) **ACTIVE** -1 (fd)
via E (q)via C 5 3
C EIGRP FD AD Topology(a) 3 (fd)
via B 3 1 (Successor)via D via E
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DUAL ExampleDUAL Example
R
(1)
(1)
(1)
(2)(2)
(a)
A
E
D
C
B
E EIGRP FD AD Topology (a) 4 (fd)
via C 4 3 (Successor)via D
D EIGRP FD AD Topology(a) **ACTIVE** -1 (fd)
via E (q)via C 5 3
C EIGRP FD AD Topology(a) 3 (fd)
via B 3 1 (Successor)via Dvia E
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DUAL ExampleDUAL Example
R
(1)
(1)
(1)
(2)(2)
(a)
A
E
B
E EIGRP FD AD Topology (a) 4 (fd)
via C 4 3 (Successor)via D
D EIGRP FD AD Topology(a) 5 (fd)
via C 5 3 (Successor)via E 5 4 (Successor)
C EIGRP FD AD Topology(a) 3 (fd)
via B 3 1 (Successor)via Dvia E
D
C
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DUAL ExampleDUAL Example
(1)
(1)
(1)
(2)(2)
(a)
A
E
D
C
B
E EIGRP FD AD Topology (a) 4 (fd)
via C 4 3 (Successor)via D
D EIGRP FD AD Topology(a) 5 (fd)
via C 5 3 (Successor)via E 5 4 (Successor)
C EIGRP FD AD Topology(a) 3 (fd)
via B 3 1 (Successor)via Dvia E
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DUAL Example (Start) DUAL Example (Start)
(1)
(1)
(1)
(1)
(2)(2)
(a)
A
E
D
C
B
E EIGRP FD AD Topology (a) 3 (fd)
via D 3 2 (Successor)via C 4 3
D EIGRP FD AD Topology(a) 2 (fd)
via B 2 1 (Successor)via C 5 3
C EIGRP FD AD Topology(a) 3 (fd)
via B 3 1 (Successor)via D 4 2 (fs)via E 4 3
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DUAL Example (End)DUAL Example (End)
(1)
(1)
(1)
(2)(2)
(a)
A
E
D
C
B
E EIGRP FD AD Topology (a) 4 (fd)
via C 4 3 (Successor)via D
D EIGRP FD AD Topology(a) 5 (fd)
via C 5 3 (Successor)via E 5 4 (Successor)
C EIGRP FD AD Topology(a) 3 (fd)
via B 3 1 (Successor)via Dvia E
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Protocol-dependent modules (PDM)Protocol-dependent modules (PDM)PDM is responsible for all functions
related to its specific routed protocol
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Protocol-dependent modules (PDM)Protocol-dependent modules (PDM)PDM can ►Support for routed protocols such as IP, IPX, and
AppleTalk ►Easily adapt to new or revised routed protocols
Sending and receiving EIGRP packets that bear IP data►Notifying DUAL of new IP routing information that is
received ►Maintaining the results of DUAL's routing decisions in
the IP routing table ►Redistributing routing information that was learned by
other IP-capable routing protocols
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EIGRP ComponentsEIGRP Components
Relies on several different kinds of packets to maintain its various tables and establish complex relationships with neighbor routers
The 5 EIGRP packet types are listed here: ►Hello : Establish neighbor relationships►Acknowledgment :Acknowledgement of a reliable
packet►Update : Send routing updates►Query : Ask neighbors about routing information►Reply : Response to query about routing information
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EIGRP Components - EIGRP Components - HelloHelloUse for Discover, verify & rediscover neighbor
routers.Hello packets are
multicast : 224.0.0.10Send hellos at a hello
interval. Default value:EIGRP routers do not receive each other's hellos
for a hold time interval (3 times hello interval):►Rediscovery occurs and then re-establish
communication.►DUAL must step in to re-evaluate the routing table
No need same hello and dead intervals to communicate.
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EIGRP Components – EIGRP Components – AcknowledgmentAcknowledgment
To indicate receipt of any EIGRP packet during a "reliable" exchange.
Recall that RTP can provide reliable communication between EIGRP hosts
"dataless" hello packets unicast.Hello packets are always sent unreliably
and thus do not require acknowledgment
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EIGRP Components – EIGRP Components – UpdateUpdate New neighbor:►Use when a router discovers a new neighbor.►EIGRP router sends unicast update packets
(maybe more than one) to new neighbor it can add to its topology table.
Old neighbor:►Use when a router detects a topology change ►Sends a multicast update packet to all
neighborsUpdate packets are sent reliably
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EIGRP Components - EIGRP Components - Query and ReplyQuery and Reply
EIGRP router loses its successor and cannot find a feasible successor for a route:►DUAL places the route in the active state►Send multicasts a query to all neighbors for searching
a successor to destination.►Neighbors must send unicast replies that either
provide information on successors or indicate that no successor information is available
Both packet types are sent reliably
A B
Need specific information from B
query packets - multicast
reply packet - unicast
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EIGRP tablesEIGRP tables
DUAL can select alternate routes based on the tables kept by EIGRP
EIGRP router can track all the routing information in an AS, not just the "best" routes
EIGRP have 3 tables:►neighbor table►routing table►topology table
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EIGRP tablesEIGRP tables – – NeighborNeighbor
Neighbor relationships tracked in the neighbor table is the basis for all the EIGRP routing update and convergence activity.
Contains information about adjacent neighboring, new neighbor is discovered New entry.
Is used to support reliable, sequenced delivery of packets
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EIGRP tables – EIGRP tables – NeighborNeighbor
Neighbor address (Address)►The network-layer address of the neighbor
router
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EIGRP tables – EIGRP tables – NeighborNeighbor
Hold time (Hold Uptime) ►Interval to wait without receiving anything
from a neighbor before considering the link unavailable
►EIGRP packets received after the first hello will reset the timer
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EIGRP tables – EIGRP tables – NeighborNeighbor
Smooth Round-Trip Timer (SRTT)►Average time that it takes to send and receive
packets from a neighbor.►This timer is used to determine the retransmit
interval (RTO)
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EIGRP tables – EIGRP tables – NeighborNeighbor
Queue count (Q Cnt)►Number of packets waiting in queue to be
sent►Q Cnt:
=0: No EIGRP packets in the queue>0:May be a congestion problem at the router
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EIGRP tablesEIGRP tables – – RoutingRouting
Contains the routes installed by DUAL as the best loop-free paths to a given destination.
Maintain up to four routes (can be of equal or unequal cost) per destination
Maintain a separate routing table for each routed protocol.
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EIGRP tablesEIGRP tables – – TopologyTopology
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EIGRP tablesEIGRP tables – – TopologyTopology
Store all the information it needs to calculate a set of distances and vectors to all reachable destinations
Maintains a separate topology table for each routed protocol
Is made up of all the EIGRP routing tables in the autonomous system.
By tracking this information, EIGRP routers can find alternate routes quickly
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EIGRP tablesEIGRP tables – – TopologyTopology
Topology table have:►Feasible distance (FD is xxxx)►Route source (via xxx.xxx.xxx.xxx)►Reported distance (RD)
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EIGRP tablesEIGRP tables – – TopologyTopology
RTA's routing table includes a route to Z via RTB (current successor). RTA Should be have at least one successor for Z for DUAL to place it in the routing table
RTC claims to have a route to Z with the exact same metric as RTB DUAL will install a second route to Z.
RTA's other neighbors that advertise a loop-free route to Z (with RD > the best-route metric and < FD) will be identified as feasible successors in the topology table.►Note: RD = Reported Distance, FD = Feasible Distance.
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EIGRP tablesEIGRP tables – – TopologyTopologySuccessor down DUAL identify a FS
from the topology table and install a new route to the destination.
No FS to the destination exist, DUAL places the route in the active state
Entries in the topology table can be in one of two states: ►Active or Passive►These states identify the status of the route
indicated by the entry rather than the status of the entry itself.
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EIGRP tablesEIGRP tables – – TopologyTopologyA passive route is one that is stable and
available for use. An active route is a route in the process of being
recomputed by DUAL. ►Re-computation happens if a route becomes
unavailable and DUAL can not find any feasible successors.
►When this occurs, the router must ask neighbors for help in finding a new, loop-free path (feasible successors) to the destination.
►Neighbor routers are compelled to reply to this query:If a neighbor has a route, it will reply with
information about the successor(s). If not, the neighbor notifies the sender that it does
not have a route to the destination either.
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"Stuck in Active" (SIA) Routes"Stuck in Active" (SIA) Routes
DUAL always tries to find a feasible successor before resorting to a re-computation. If a feasible successor is available, DUAL can quickly install the new route and avoid re-computation.
The route(s) in "stuck in active" state : If one or more routers to which a query is sent do not respond with a reply within the active time of 180 seconds (3 minutes).
EIGRP clears the neighbors that did not send a reply and logs a "stuck in active" error message for the route(s) that went active.
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Route tagging with EIGRPRoute tagging with EIGRP
EIGRP classifies routes as either internal or external EIGRP uses route tagging to add special tags to each route
Tags identify route as :►Internal ►External ►Other
information
5252
Route tagging with EIGRPRoute tagging with EIGRP
Static routes are external routesExternal routes are included in the topology
table and are tagged with the following information:1.The router ID of the EIGRP router that redistributed
the route into the EIGRP network 2.The AS number of the destination 3.The protocol used in that external network 4.The cost or metric received from that external
protocol 5.The configurable administrator tag
Tag to be any number between 0 and 255
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EIGRP Operation EIGRP Operation
DUAL's sophisticated algorithm results in EIGRP's exceptionally fast convergence
5454
EIGRP OperationEIGRP Operation RTA choose RTY = Successor (lowest computed cost) 31 = FD to Network 24 RTY down RTA try to use FS.
5555
EIGRP OperationEIGRP Operation
RTA follows a three-step process:1. Determine which neighbors have a RD < FD
to network 24 RTX's RD is 302. Determine the minimum computed cost to
Network 24 : RTX is 40 RTX provides the lowest computed cost.
3. Determine whether any routers that met the criterion in Step 1 also met the criterion in Step 2. RTX has done both, so it is the feasible successor.
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EIGRP OperationEIGRP Operation RTY down, RTA uses RTX (FS) forward packets to Network 24 If RTX also becomes unavailable:
► RTZ cannot be a feasible successor because RD =220 > FD=31 And The FD can change only during an active-to-passive transition
DUAL has been performing what is called a local computationRTA cannot find any FS transitions passive to active state queries its neighbors diffusing computation Network 24 is active state the FD is reset RTA to at last accept RTZ as the successor
5757
Configuring EIGRPConfiguring EIGRP
1. Configuring EIGRP for IP networks 2. EIGRP and the bandwidth command and The
bandwidth-percent command 3. Configuring EIGRP for IPX networks 4. Controlling SAP updates 5. Summarizing EIGRP routes for IP 6. Variance
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For IP networksFor IP networks
1. router(config)# router eigrp autonomous-system-number► AS much match all router inside AS
2. router(config-router)# network network-number► Network number only for connected network
3. router(config-if)# bandwidth kilobits ► Serial interface link use (if not Router take default)
router(config-if)# eigrp log-neighbor-changes► Enables the logging of neighbor adjacency changes
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For IP networksFor IP networks
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EIGRP Bandwidth UtilizationEIGRP Bandwidth Utilization
Specifies what percentage of bandwidth EIGRP packets will be able to utilize on this interface
Uses up to 50% of the link bandwidth for EIGRP packets, by default ►Used for greater EIGRP load control
ip bandwidth-percent eigrp as-number percent ipx bandwidth-percent eigrp appletalk eigrp-bandwidth-percent
6161
EIGRP & Bandwidth over WANEIGRP & Bandwidth over WAN
EIGRP supports different WAN links►Point-to-point►NBMA
MultipointPoint-to-point
EIGRP configurations must address►Bandwidth utilization►Overhead traffic associated with router
operation
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Bandwidth over WAN InterfacesBandwidth over WAN Interfaces
Bandwidth utilization over point-to-point subinterfaces using Frame Relay►Treats bandwidth as T1, by default►Best practice is to manually configure
bandwidth as the CIR of the PVC
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Bandwidth over WAN InterfacesBandwidth over WAN Interfaces
Bandwidth over multipoint Frame Relay, ATM, SMDS, and ISDN PRI:►EIGRP uses the bandwidth on the main
interface divided by the number of neighbors on that interface to get the bandwidth information per neighbor
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Bandwidth over WAN InterfacesBandwidth over WAN Interfaces
Each PVC might have a different CIR, this might create an EIGRP packet pacing problem►Multipoint interfaces:
Convert to point-to-point configuration, orManually configure bandwidth =
(lowest CIR x number of PVCs)
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EIGRP WAN Configuration — Pure EIGRP WAN Configuration — Pure MultipointMultipoint
CIR 56
C
EF G
H
FrameRelay
S0
CIR 56 CIR 56
CIR 56
T1
interface serial 0 encap frame-relay bandwidth 224
• All VCs share bandwidth evenly: 4 x 56 = 224
6666
EIGRP WAN Configuration — Hybrid EIGRP WAN Configuration — Hybrid MultipointMultipoint
CIR 256BW 224
C
EF G
H
FrameRelay
S0
CIR 256BW 224
CIR 256BW 224
CIR 56BW 56
T1
• Lowest CIR x # of VC: 56 x 4 = 224
interface serial 0 encap frame-relay bandwidth 224
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EIGRP WAN Configuration— Hybrid EIGRP WAN Configuration— Hybrid Multipoint (Preferred)Multipoint (Preferred)
CIR 256BW 256
C
EF G
H
FrameRelay
S0
CIR 256BW 256
CIR 256BW 256
CIR 56BW 56
T1
interface serial 0.1 multipoint bandwidth 768
interface serial 0.2 point-to-point bandwidth 56
• Configure lowest CIR VC as point-to-point, specify BW = CIR• Configure higher CIR VCs as multipoint, combine CIRs
S0.1S0.2
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EIGRP WAN Configuration — Pure EIGRP WAN Configuration — Pure Point-to-PointPoint-to-Point
CIR 56BW 25
C
EF G
H
FrameRelay
S0
CIR 56BW 25
CIR 56BW 25
CIR 56BW 25
256
interface serial 0.1 point-to-point bandwidth 25 ip bandwidth-percent eigrp 63 110 - - - - interface serial 0.10 point-to-point bandwidth 25 ip bandwidth-percent eigrp 63 110
• Configure each VC as point-to-point, specify BW = 1/10 of link capacity• Increase EIGRP utilization to 50% of actual VC capacity
interface serial 0 bandwidth 25 ip bandwidth-percent eigrp 63 110
Hub and Spokewith 10x VCs
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For IPX networks & SAP updateFor IPX networks & SAP update
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For IPX networks & SAP updateFor IPX networks & SAP update Enable EIGRP for IPX, perform the
following steps:► Enable IPX routing: router(config)# ipx routing► Define EIGRP as the IPX routing protocol:
router(config-router)# ipx router {eigrp as-number | rip}
► Indicate networks: router(config-ipx-router)# network network-number
► (Optional) If IPX RIP is also operating on the router, remove RIP:router(config-ipx-router)# no network network-number
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For IPX networks & SAP updateFor IPX networks & SAP updateBy Default, Cisco routers redistribute IPX
RIP routes IPX EIGRP routes.RIP route to a destination with a hop count
of 1 is always preferred over an EIGRP route with a hop count of 1 (exception if both the RIP and EIGRP updates were received from the same router)
Controlling IPX RIP►RouterRouter: EIGRP►LAN Router:RIP(default)
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For IPX networks & SAP updateFor IPX networks & SAP update
To reduce the amount of bandwidth required to send SAP updates periodically:► router(config-if)#ipx sap-
incremental eigrp as-number [rsup-only]
► rsup-only: Indicate on this interface the
system uses EIGRP to carry reliable SAP update information only.
RIP routing updates are used EIGRP routing updates are
ignored
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Summarizing EIGRP routes – Summarizing EIGRP routes – AutoAutoEIGRP automatically summarizes routes at the
classfulIf you have discontiguous subnetworks Auto-
summarizes need disable
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Summarizing EIGRP routes – Summarizing EIGRP routes – ManualManual
router(config-if)#ip summary-address eigrp autonomous-system-number ip-address mask administrative-distance
Example:RTC(config)#router eigrp 2446RTC(config-router)#no auto-summaryRTC(config-router)#exitRTC(config)#interface serial0RTC(config-if)#ip summary-address eigrp 2446 2.1.0.0 255.255.0.0
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EIGRP Load BalancingEIGRP Load Balancing
Routes with metric equal to the minimum metric will be installed in the routing table (equal-cost load balancing)
Up to six entries in the routing table for the same destination►Number of entries is configurable►Default is four
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EIGRP Unequal-Cost Load BalancingEIGRP Unequal-Cost Load Balancing
EIGRP offers unequal-cost load balancing►variance command
Variance allows the router to include routes with a metric smaller than multiplier times the minimum metric route to that destination►Multiplier is the number specified by the
variance command
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10
20
10
10
20
25variance 2
Variance ExampleVariance Example
Router E will choose Router C to get to Network Z because FD = 20
With variance of 2, Router E will also choose Router B to get to Network Z (20 + 10) < (2 x [FD])
Router D will not be used to get to Network Z (45 > 40)
Network Z(config)#
AE
D
C
B
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Verify EIGRP with Verify EIGRP with Show Show commandcommandCommand Description
Show ip eigrp neighbors [int type] [details]
Display EIGRP neighbor table
Show ip eigrp interfaces [int type] [as-number][details]
Displays EIGRP statistics and status information
Show ip eigrp topology [as-number][ [ip-add] mask ]
Display the EIGRP topology table, use the show ip eigrp topology EXEC command. Also used to determine DUAL states & debug possible DUAL problems.
Show ip eigrp topology [active | pending | zero-successor]
Depending on keyword is used. Display all routes in the topology table that are either active, pending or without successor
Show ip eigrp all-links Display all routes not just FC in EIGRP topology
Show ip eigrp traffic [as-number]
Display the number of EIGRP packets send and received.
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Verify EIGRP with Verify EIGRP with Debug Debug commandcommandCommand Description
Debug eigrp fsm This command helps you observe EIGRP FS activity and to determine whether route updates are being installed and deleted by the routing process
debug eigrp packet Displays all types of EIGRP packets, both sent and received
debug eigrp neighbor Displays the EIGRP neighbor interactiondebug ip eigrp route Displays advertisements and changes EIGRP
makes to the routing tabledebug ip eigrp summary
Displays a brief report of the EIGRP routing activity
show ip eigrp events Displays the different categories of EIGRP activity, including route calculations
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SummarySummaryEIGRP, a routing protocol developed by
Ciscoadvanced distance-vector routing protocol
that uses the DUAL algorithmMajor feature:►Rapid convergence converges rapidly
based-on DUAL►Reduced bandwidth usage summarizes
routes, performs incremental updates►Multiple network-layer support IP, IPX, and
AppleTalk traffic
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Remember all EIGRP FeatureRemember all EIGRP Feature1. Advanced distance vector2. 100% loop free3. Fast convergence4. Easy configuration5. Less network design constraints than OSPF6. Incremental updates7. Supports VLSM and discontiguous networks8. Classless routing9. Compatible with existing IGRP networks10.Protocol independent (supports IP, IPX and
AppleTalk)
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EIGRP Scalability RulesEIGRP Scalability Rules
EIGRP is a very scalable routing protocol if proper design methods are used:►Good allocation of address space: Each
region should have a contiguous address space so route summarization is possible
►Have a tiered network design model
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Core
TokenRing
TokenRing
3.3.4.01.1.1.0
3.3.4.0
1.1.4.0
3.3.3.0
2.2.1.0
1.1.3.0
3.3.1.0
1.1.2.02.2.3.0
2.2.2.0
TokenRing
TokenRing
TokenRing
TokenRing
1.1.1.01.1.2.02.2.3.03.3.4.0
2.2.1.03.3.2.03.3.3.01.1.4.0
3.3.1.02.2.2.01.1.3.0
Nonscalable Network — ExampleNonscalable Network — Example
Bad addressing scheme►Subnets are everywhere throughout entire network
Queries not bounded
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Core
3.0.0.0
2.0.0.0
TokenRing
TokenRing
1.1.4.01.1.1.0
3.3.4.0
3.3.4.0
3.3.3.0
3.3.1.0
2.2.3.0
2.2.1.0
1.1.3.0
1.0.0.0
TokenRing
TokenRing
TokenRing
TokenRing
Scalable Network — ExampleScalable Network — Example
Readdress the network Each region has its own block of addresses
Queries bounded by using ip summary-address eigrp command
1.1.2.0
2.2.2.0
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Regional Office
Remote Office
Summarized Routes
Summarized RoutesSummarized Routes
Summarized Routes
Summarized Routes Summarized Routes
Tiered Network DesignTiered Network Design
OtherRegions
Core
OtherRegions
OtherRegions
OtherRegions
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More EIGRP Scalability RulesMore EIGRP Scalability Rules
Proper network resources:►Sufficient memory on the router►Sufficient bandwidth on WAN interfaces
Proper configuration of the bandwidth statement over WAN interfaces, especially over Frame Relay
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Question/AnswerQuestion/Answer
1. How are IGRP and EIGRP different in their metric calculation?
2. Why are EIGRP routing updates described as “reliable?”
3. What does it mean when a route is marked as a feasible successor?
4. What is the recommended practice for configuring bandwidth on a Frame Relay point-to-point subinterface?
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Question/AnswerQuestion/Answer Matching terms with statements. Place the letter of the description in front
of the term that the statement describes. A statement may describe several terms.
_____ 1. Successor A) A network protocol that EIGRP supports
_____ 2. FS B) A table that contains feasible successor information
_____ 3. Hello C) Administrative distance determines routing information that is included in this table.
_____ 4. Topology table D) A neighbor router that has the best path to a destination
_____ 5. IP E) A neighbor router that has the best alternative path to a destination
_____ 6. Update F) An algorithm used by EIGRP that assures fast convergence
_____ 7. AppleTalk G) A multicast packet used to discover neighbors
_____ 8. Routing table H) A packet sent by EIGRP routers when a new neighbor is discovered and when a change occurs
_____ 9. DUAL _____ 10. IPX