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EIGRP FOR MANAGED SERVICES TECHNOLOGY DEPLOYMENT

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1 EIGRP FOR MANAGED SERVICES TECHNOLOGY DEPLOYMENT
SANGITA PANDYA INTERNET TECHNOLOGIES DIVISION DECEMBER 2004 1 1 1

2 Agenda INTRODUCTION Fundamentals of EIGRP
DUAL Summarization and Load Balancing Query Process Deployment Guidelines with EIGRP Summary Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 2 2 2

3 VPN for Many Managed Services
V i r t u a l P r i v a t e N e t w o r k MANAGED Routing MANAGED Security MANAGED CPE Service Level Agreement for MANAGED Services MANAGED IPT MANAGED Internet Gateway MANAGED Extranet Service Provider Converged Network Describe why IP VPN is important for Cisco & the need to churn customers from FR/ATM to IP Show how IP VPN can help SP by providing the foundation to layer multiple services. This helps SP & Cisco grow their revenue. Highlight the concept of one network many services – this resonates with SP. (we can draw the parallel with voice network, which allowed SP to offer basic voice & then layer in high margin services like Caller ID, Call Block, 3-way calling etc. There was very little incremental cost to SP to deliver these additional services as these feature were built into the PSTN IN) VM VM Customer Branch VPN B Customer HQ

4 Managed Routing Revenue Opportunity
Over 50% of Cisco Enterprise Customers Deploy IP Routing with EIGRP IP/MPLS VPN Backbone PE-3 PE-1 PE-2 CE-1 CE-2 EIGRP AS-1 EIGRP AS-1

5 Robust EIGRP Support Cisco Exclusive
Cisco IOS Supports the Industry’s Most Comprehensive and Robust Routing Protocol Support: RIP, OSPF, BGP, ISIS, Including EIGRP CEA2 VPN C/Site 2 12.1/16 CE1B1 Static CEB2 16.2/16 RIPv2 RIPv2 P1 PE2 VPN B/Site 2 BGP RIPv2 PE1 P2 CEA3 OSPF OSPF Cisco IOS® supports the industry’s most comprehensive and robust routing protocol support RIP, EIGRP, OSPF, BGP, ISIS Full encrypted secure MD5 route exchange Cisco IOS® enables smooth migration of enterprise’s existing architecture by wide range of CE to PE routing options 16.2/16 CEA1 P3 PE3 BGP VPN A/Site 1 CEB3 VPN A/Site 2 16.1/16 12.2/16 VPN C/Site 1 BENEFITS: Service Provider: Simplest point of entry into enterprise’s existing architecture Enterprise: Least disruption to current network design

6 Managed EIGRP Benefits for SPs and Enterprises:
Impose little requirements or no restrictions on customer networks CE and C routers are NOT required to run newer code (CE/C upgrades recommended for full SoO functionality) Customer sites may be same or different autonomous systems Customer sites may consist of several connections to the MPLS VPN backbone Customer sites may consist of one or more connections not part of the MPLS VPN backbone (“backdoor” links) 6 6 6

7 Introducing EIGRP EIGRP is architected by Cisco systems to overcome short comings of other protocols such as RIP, IGRP and OSPF It is widely deployed in Enterprise networks MPLS VPN Service Providers also enable EIGRP on their PE routers to support the connecting networks which may already be running EIGRP EIGRP can also be used as CE-PE routing protocol for MPLS VPN connectivity

8 IGRP: Interior Gateway Routing Protocol
Cisco proprietary Distance vector Broadcast based Utilizes link bandwidth and delay 15 hops is no longer the limit 90 seconds updates (RIP is 30 sec.) Load balance over unequal cost paths

9 IGRP/EIGRP Metrics Calculation
Metric = [K1 x BW + (K2 x BW) / (256 - Load) + K3 x Delay] x [K5 / (Reliability + K4)] By Default: K1 = 1, K2 = 0, K3 = 1, K4 = K5 = 0 Delay is sum of all the delays of the link along the paths Delay = Delay/10 Bandwidth is the lowest bandwidth of the link along the paths Bandwidth = /Bandwidth

10 Problems with RIP and IGRP
Slow convergence Not 100% loop free Don’t support VLSM and discontiguous network Periodic full routing updates RIP has hop count limitation

11 Advantages of EIGRP Advanced distance vector 100% loop free
Fast convergence Easy configuration Less network design constraints than OSPF Incremental update Supports VLSM and discontiguous network Classless routing Compatible with existing IGRP network Protocol independent (support IPX and AppleTalk) Connects MPLS VPN subscribers to their provides seamlessly

12 Advantages of EIGRP Uses multicast instead of broadcast
Utilize link bandwidth and delay EIGRP Metric = IGRP Metric x 256 (32 bit vs. 24 bit) Unequal cost paths load balancing More flexible than OSPF Full support of distribute list Manual summarization can be done in any interface at any router within network

13 EIGRP Packets Hello: Establish neighbor relationships
Update: Send routing updates Query: Ask neighbors about routing information Reply: Response to query about routing information Ack: Acknowledgement of a reliable packet

14 EIGRP Neighbor Relationship
Two routers become neighbors when they see each other’s hello packet Hello address = Hellos sent once every five seconds on the following links: Broadcast Media: Ethernet, Token Ring, FDDI, etc. Point-to-point serial links: PPP, HDLC, point-to-point frame relay/ATM subinterfaces Multipoint circuits with bandwidth greater than T1: ISDN PRI, SMDS, Frame Relay

15 EIGRP Neighbor Relationship
Hellos sent once every 60 seconds on the following links: Multipoint circuits with bandwidth less than or equal to T1: ISDN BRI, Frame Relay, SMDS, etc. Neighbor declared dead when no EIGRP packets are received within hold interval Not only Hello can reset the hold timer Hold time by default is three times the hello time

16 EIGRP Neighbor Relationship
EIGRP will form neighbors even though hello time and hold time don’t match EIGRP sources hello packets from primary address of the interface EIGRP will not form neighbor if K-values are mismatched EIGRP will not form neighbor if AS numbers are mismatched Passive interface (IGRP vs. EIGRP)

17 I am Router A, Who Is on the Link?
Discovering Routes A B 1 afadjfjorqpoeru I am Router A, Who Is on the Link? Hello

18 Discovering Routes A B 1 2 I am Router A, Who Is on the Link? Hello
afadjfjorqpoeru I am Router A, Who Is on the Link? Hello afadjfjorqpoeru 2 Here Is My Routing Information (Unicast) Update

19 Discovering Routes A B 1 2 3 I am Router A, Who Is on the Link? Hello
afadjfjorqpoeru I am Router A, Who Is on the Link? Hello afadjfjorqpoeru 2 Here Is My Routing Information (Unicast) Update 3 afadjfjorqpoeru Thanks for the Information! Ack

20 Discovering Routes A B 1 2 4 3 I am Router A, Who Is on the Link?
afadjfjorqpoeru I am Router A, Who Is on the Link? Hello afadjfjorqpoeru 2 Here Is My Routing Information (Unicast) Update 4 3 afadjfjorqpoeru Thanks for the Information! Ack Topology Table

21 Discovering Routes A B 1 2 4 3 5 I am Router A, Who Is on the Link?
afadjfjorqpoeru I am Router A, Who Is on the Link? Hello afadjfjorqpoeru 2 Here Is My Routing Information (Unicast) Update 4 3 afadjfjorqpoeru Thanks for the Information! Ack Topology Table 5 afadjfjorqpoeru Here Is My Route Information (Unicast) Update

22 Discovering Routes Converged A B 1 2 4 3 5 6
afadjfjorqpoeru I am Router A, Who Is on the Link? Hello afadjfjorqpoeru 2 Here Is My Routing Information (Unicast) Update 4 3 afadjfjorqpoeru Thanks for the Information! Ack Topology Table 5 afadjfjorqpoeru Here Is My Route Information (Unicast) Update afadjfjorqpoeru Thanks for the Information! 6 Ack Converged

23 Agenda Fundamentals of EIGRP DUAL Summarization and Load Balancing
Query Process Deployment Guidelines with EIGRP Summary 23 23 23

24 EIGRP DUAL Diffusing update algorithm Finite-State-Machine
Track all routes advertised by neighbors Select loop-free path using a successor and remember any feasible successors If successor lost Use feasible successor If no feasible successor Query neighbors and recompute new successor

25 EIGRP Feasible Distance (FD)
Feasible distance is the minimum distance (metric) along a path to a destination network

26 Feasible Distance Example
Network 7 (20) (10) (100) H G (1) B C A (100) D E F (10) (100) (100) (20) Destination Feasible Distance (FD) Neighbor Topology Table 7 =130 H 7 =121 B 7 =240 D

27 EIGRP Reported Distance (RD)
Reported distance is the distance (metric) towards a destination as advertised by an upstream neighbor Reported distance is the distance reported in the queries, the replies and the updates

28 Reported Distance Example
Network 7 (20) (10) (100) H G (1) (100) B C A (100) D E F (10) (100) (20) Topology Table Destination Reported Distance (RD) Neighbor 7 20+10=30 H 7 =21 B 7 =140 D

29 EIGRP Feasibility Condition (FC)
A neighbor meets the feasibility condition (FC) if the reported distance by the neighbor is smaller than the feasible distance (FD) of this router

30 EIGRP Successor A successor is a neighbor that has met the feasibility condition and has the least cost path towards the destination It is the next hop for forwarding packets Multiple successors are possible (load balancing)

31 EIGRP Feasible Successor (FS)
A feasible successor is a neighbor whose reported distance (RD) is less than the feasible distance (FD)

32 Router A’s Routing Table
Successor Example Network 7 (20) (10) (100) H G (1) (100) B C A (100) Router A’s Routing Table D E F (10) (100) (20) Destination FD RD Neighbor Topology Table 7 121 B 7 130 30 H 7 121 21 B 7 240 140 D B is current successor (FD = 121) H is the feasible successor (30 < 121)

33 Passive, Active, and Stuck in Active (SIA)
Passive routes are routes that have successor information Passive route = Good Active routes are routes that have lost their successors and no feasible successors are available; the router is actively looking for alternative paths Active route = Bad Stuck in Active means the neighbor still has not replied to the original query within three minutes Stuck in active = Ugly

34 Dual Algorithm Local computation
When a route is no longer available via the current successor, the router checks its topology table Router can switch from successor to feasible successor without involving other routers in the computation Router stays passive Updates are sent

35 DUAL: Local Computation
(10) #7 H #2 #8 #1 G A (20) #6 B #3 C (10) X (1) (100) (10) #7 121/21 B #7 130/30 H . . . D F E #4 #5 (100) (20)

36 Dual Algorithm Diffused Computation
When a route is no longer available via its current successor and no feasible successor is available, queries are sent out to neighbors asking about the lost route The route is said to be in active state Neighbors reply to the query if they have information about the lost route; if not, queries are sent out to all of their neighbors The router sending out the query waits for all of the replies from its neighbors and will make routing decision based on the replies

37 DUAL: Diffused Computation
(10) #7 X H #2 #8 #1 G A (20) #6 B C (10) X #3 (1) (100) (10) #7 121/21 B #7 130/30 H . . . D F E #4 #5 (100) (20)

38 X DUAL Example (a) C EIGRP Topology (a) Cost (3) (fd)
via B Cost (3/1) (Successor) via D Cost (4/2) (fs) via E Cost (4/3) A (1) D EIGRP Topology (a) Cost (2) (fd) via B Cost (2/1) (Successor) via C Cost (5/3) (1) X B D (2) (2) (1) E EIGRP Topology (a) Cost (3) (fd) via D Cost (3/2) (Successor) via C Cost (4/3) (1) C E

39 DUAL Example (a) C EIGRP Topology (a) Cost (3) (fd)
via B Cost (3/1) (Successor) via D via E Cost (4/3) A (1) D EIGRP Topology (a) **ACTIVE** Cost (-1) (fd) via E (q) via C Cost (5/3) (q) B D (2) (2) (1) Q E EIGRP Topology (a) Cost (3) (fd) via D Cost (3/2) (Successor) via C Cost (4/3) Q (1) C E

40 DUAL Example (a) C EIGRP Topology (a) Cost (3) (fd)
via B Cost (3/1) (Successor) via D via E A (1) D EIGRP Topology (a) **ACTIVE** Cost (-1) (fd) via E (q) via C Cost (5/3) B D (2) R (2) (1) E EIGRP Topology (a) **ACTIVE** Cost (-1) (fd) via D via C Cost (4/3) (q) (1) C E Q

41 DUAL Example (a) C EIGRP Topology (a) Cost (3) (fd)
via B Cost (3/1) (Successor) via D via E A (1) D EIGRP Topology (a) **ACTIVE** Cost (-1) (fd) via E (q) via C Cost (5/3) B D (2) (2) (1) E EIGRP Topology (a) Cost (4) (fd) via C Cost (4/3) (Successor) via D (1) C E R

42 DUAL Example (a) C EIGRP Topology (a) Cost (3) (fd)
via B Cost (3/1) (Successor) via D via E A (1) D EIGRP Topology (a) Cost (5) (fd) via C Cost (5/3) (Successor) via E Cost (5/4) (Successor) B D R (2) (2) (1) E EIGRP Topology (a) Cost (4) (fd) via C Cost (4/3) (Successor) via D (1) C E

43 DUAL Example (a) C EIGRP Topology (a) Cost (3) (fd)
via B Cost (3/1) (Successor) via D via E A (1) D EIGRP Topology (a) Cost (5) (fd) via C Cost (5/3) (Successor) via E Cost (5/4) (Successor) B D (2) (2) (1) E EIGRP Topology (a) Cost (4) (fd) via C Cost (4/3) (Successor) via D (1) C E

44 DUAL Example (Start) (a) C EIGRP Topology (a) Cost (3) (fd)
via B Cost (3/1) (Successor) via D Cost (4/2) (fs) via E Cost (4/3) A (1) D EIGRP Topology (a) Cost (2) (fd) via B Cost (2/1) (Successor) via C Cost (5/3) (1) B D (2) (2) (1) E EIGRP Topology (a) Cost (3) (fd) via D Cost (3/2) (Successor) via C Cost (4/3) (1) C E

45 DUAL Example (End) (a) C EIGRP Topology (a) Cost (3) (fd)
via B Cost (3/1) (Successor) via D via E A (1) D EIGRP Topology (a) Cost (5) (fd) via C Cost (5/3) (Successor) via E Cost (5/4) (Successor) B D (2) (2) (1) E EIGRP Topology (a) Cost (4) (fd) via C Cost (4/3) (Successor) via D (1) C E

46 EIGRP Reliable Transport Protocol
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

47 EIGRP Reliable Transport Protocol
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 acked 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

48 EIGRP Reliable Transport Protocol
With reliable multicast traffic, one must wait to transmit the next reliable multicast packets, until all peers have acknowledged the previous multicast If one or more peers are slow in acknowledging, all other peers suffer from this Solution: The nonacknowledged multicast packet will be retransmitted as a unicast to the slow neighbor

49 EIGRP Reliable Transport Protocol
Per neighbor, retransmission limit is 16 Neighbor relationship is reset when retry limit (limit = 16) for reliable packets is reached

50 Agenda Fundamentals of EIGRP DUAL SUMMARIZATION AND LOAD BALANCING
Query Process Deployment Guidelines with EIGRP Summary

51 EIGRP Summarization Purpose: Smaller routing tables, smaller updates, query boundary Auto summarization: On major network boundaries, networks are summarized to the major networks Auto summarization is turned on by default x x

52 EIGRP Summarization Manual summarization
Configurable on per interface basis in any router within network When summarization is configured on an interface, the router immediate creates a route pointing to null zero with administrative distance of five Loop prevention mechanism When the last specific route of the summary goes away, the summary is deleted The minimum metric of the specific routes is used as the metric of the summary route

53 EIGRP Summarization Manual summarization command:
ip summary-address EIGRP <as number> <address> <mask> X AS 1 /22 X S0 interface s0 ip address X ip summary-address EIGRP

54 EIGRP Load Balancing Routes with equal metric to the minimum metric, will be installed in the routing table (Equal Cost Load Balancing) There can be up to six entries in the routing table for the same destination (default = 4) ip maximum-paths <1-6>

55 EIGRP Unequal Cost Load Balancing
EIGRP offers unequal cost load balancing feature with the command: Variance <multiplier> Variance command will allow the router to include routes with a metric smaller than multiplier times the minimum metric route for that destination, where multiplier is the number specified by the variance command

56 Variance Example Router E will choose router C to get to net X FD=20
B 20 10 E A C 10 10 Net X 20 25 Variance 2 D Router E will choose router C to get to net X FD=20 With variance of 2, router E will also choose router B to get to net X Router D will not be used to get to net X

57 Agenda Fundamentals of EIGRP DUAL Summarization and Load Balancing
QUERY PROCESS Deployment Guidelines with EIGRP Summary 57 57 57

58 EIGRP Query Process EIGRP is Advanced Distant Vector—it relies on its neighbor to provide routing information If a route is lost and no feasible successor is available, EIGRP needs to converge fast, its only mechanism for fast convergence is to actively query for the lost route to its neighbors Have You Seen My Sparky?

59 EIGRP Query Process Queries are sent out when a route is lost and no feasible successor is available The lost route is now in active state Queries are sent out to all of its neighbors on all interfaces except the interface to the successor If the neighbor does not have the lost route information, queries are sent out to their neighbors

60 EIGRP Query Process The router will have to get ALL of the replies from the neighbors before the router calculates the successor information If any neighbor fails to reply the query in three minutes, this route is stuck in active and the router resets the neighbor that fails to reply Solution is to limit query range to be covered later in presentation

61 X EIGRP Query Range Autonomous System Boundaries
Contrary to popular belief, queries are not bounded by AS boundaries. Queries from AS 1 will be propagated to AS 2 A B C X Network X AS 2 AS 1 Query for X Reply for X Query for X

62 Reply with Infinity and the Query Stops Here!
EIGRP Query Range Summarization point Auto or manual summarization bound queries Requires a good address allocation scheme A C B /24 B Summarizes /8 to A 130.x.x.x Reply with Infinity and the Query Stops Here! Query for /24 X 129.x.x.x

63 EIGRP Bandwidth Utilization
EIGRP by default will use up to 50% of the link bandwidth for EIGRP packets This parameter is manually configurable by using the command: ip bandwidth-percent EIGRP <AS-number> <nnn> Use for greater EIGRP load control

64 Bandwidth over WAN Interfaces
Bandwidth utilization over point-to-point subinterface Frame Relay Treats bandwidth as T1 by default Best practice is to manually configure bandwidth as the CIR of the PVC

65 Bandwidth 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

66 Bandwidth over WAN Interfaces
Each PVC might have different CIR, this might create EIGRP packet pacing problem Multipoint interfaces: Convert to point-to-point Bandwidth configured = (lowest CIR x number of PVC) ISDN PRI: Use Dialer Profile (treat as point-to-point link)

67 Agenda Fundamentals of EIGRP DUAL Summarization and Load Balancing
Query Process EIGRP FOR CE-PE CONNECTIVITY IN MPLS VPN NETWORKS Deployment Guidelines with EIGRP Summary 67 67 67

68 EIGRP: CE-PE Routing Protocol in MPLS VPN
Support Enhanced Interior Gateway Routing Protocol (EIGRP) routes through a Multiprotocol Label Switching (MPLS) Virtual Private Network (VPN) over a Border Gateway Protocol (BGP) core network by redistributing EIGRP into MPBGP on a provider edge router Configuration is only on PE routers and requires no upgrade or configuration changes to customer equipment Also support EIGRP extended community attributes Things an enterprise customers needs to consider: Things a Service Providers need to consider:

69 CE-PE Connectivity Things an enterprise customers needs to consider:
Things a Service Providers need to consider: Topology Ex:

70 Agenda Fundamentals of EIGRP DUAL Summarization and Load Balancing
Query Process EIGRP for CE-PE connectivity in MPLS VPN Networks DEPLOYMENT GUIDELINES WITH EIGRP Summary 70 70 70

71 Factors That Influence EIGRP Scalability
Keep in mind that EIGRP is not plug and play for large networks Limit EIGRP query range! Quantity of routing information exchanged between peers The following factors (and others) impact how scalable a network is: The amount of information being exchanged between neighbors. If more information is passed than necessary for routing to function correctly, EIGRP will have to work harder at neighbor startup and reacting to changes in the network. When a change occurs in the network, the amount of resources consumed by EIGRP will be directly related to the number of routers that must be involved in the change. This will be explained in more detail in the troubleshooting section of this presentation. The depth of the topology is also a factor in how scalable a network is. . This describes the situation where you have to propagate the information through many hops (depth) for convergence. A Multinational network without summarization is an example of this type of condition. The number of alternative paths through the network can also impact scalability in a network. A network should provide alternative paths in order to avoid single points of failure. Too much complexity (alternative paths), however, can also create problems with EIGRP converging. More on this later.

72 Limiting Updates/Queries—Example
Distribution Layer Remote Sites /24 RTRC RTRB RTRD In the sample network above, each dual-home remote router would be seen as an alternative path to from RTRA unless information hiding techniques are used. With the summary-address commands on the outbound interfaces of RTRA and RTRB, components are not sent to the remote routers at all, so they will not reflect the routes back to the distribution layer. Likewise, the distribute-list out commands would be installed at the remote routers to limit their advertisements to only those networks that exist at that remote site. Therefore, they won’t even reflect the summary route from RTRA back to RTRB, nor will they reflect the summary route from RTRB back to RTRA. This will minimize the part the remote routers play in the update and query process and will increase the stability and scalability of this network. RTRA RTRE

73 Limiting Size/Scope of Updates/Queries
Evaluate routing requirements What routes are needed where? Once needs are determined Use summary address Use new EIGRP Stub feature (To be discussed later) Use distribute lists Very seldom do remote routers need to know all of the routes being advertised in the entire network. The network manager needs to look at what information is necessary to properly route user traffic to where it needs to go. There are trade-offs between how much information is supplied to the remote routers to provide the desire level of path selection. In other words, maximum stability/scalability is felt when the remote routers only use a default route to reach the core. If some component knowledge needs to be allowed so that optimum path selection can take place for those targets, then a business decision needs to be made, Once the minimum requirements are determined, either summary-address statements need to be added on the outbound interfaces of the routers or distribute-lists added to the router process. These are used to limit what information is provided to the end system.

74 Limiting Updates/Queries—Example
Distribution Layer Remote Sites /24 X Queries Replies RTRC RTRB RTRD In the sample network above, each dual-home remote router would be seen as an alternative path to from RTRA unless information hiding techniques are used. With the summary-address commands on the outbound interfaces of RTRA and RTRB, components are not sent to the remote routers at all, so they will not reflect the routes back to the distribution layer. Likewise, the distribute-list out commands would be installed at the remote routers to limit their advertisements to only those networks that exist at that remote site. Therefore, they won’t even reflect the summary route from RTRA back to RTRB, nor will they reflect the summary route from RTRB back to RTRA. This will minimize the part the remote routers play in the update and query process and will increase the stability and scalability of this network. RTRA RTRE

75 Limiting Updates/Queries—Summary
Remote routers fully involved in convergence Most remotes are never intended to be transit Convergence complicated through lack of information hiding

76 Limiting Updates/Queries—Better
/24 RTRB RTRA RTRC RTRD RTRE Distribution Layer Remote Sites Queries Replies X In the sample network above, each dual-home remote router would be seen as an alternative path to from RTRA unless information hiding techniques are used. With the summary-address commands on the outbound interfaces of RTRA and RTRB, components are not sent to the remote routers at all, so they will not reflect the routes back to the distribution layer. Likewise, the distribute-list out commands would be installed at the remote routers to limit their advertisements to only those networks that exist at that remote site. Therefore, they won’t even reflect the summary route from RTRA back to RTRB, nor will they reflect the summary route from RTRB back to RTRA. This will minimize the part the remote routers play in the update and query process and will increase the stability and scalability of this network. IP summary-address EIGRP on all outbound interfaces to remotes

77 Limiting Updates/Queries—Summary
Convergence simplified by adding the summary-address statements Remote routers just reply when queried

78 Limiting Updates/Queries New Feature
New EIGRP STUB command is now available (12.0.7T and higher) [no] EIGRP stub [receive-only] [connected] [static] [summary] Only specified routes are advertised. Any neighbor receiving “stub” information from a neighbor will not query those routers for any routes

79 Limiting Updates/Queries—Best
Best practice is to combine Summarization and EIGRP STUB command

80 Limiting Updates/Queries—Best
/24 RTRB RTRA RTRC RTRD RTRE Distribution Layer Remote Sites X Queries Replies In the sample network above, each dual-home remote router would be seen as an alternative path to from RTRA unless information hiding techniques are used. With the summary-address commands on the outbound interfaces of RTRA and RTRB, components are not sent to the remote routers at all, so they will not reflect the routes back to the distribution layer. Likewise, the distribute-list out commands would be installed at the remote routers to limit their advertisements to only those networks that exist at that remote site. Therefore, they won’t even reflect the summary route from RTRA back to RTRB, nor will they reflect the summary route from RTRB back to RTRA. This will minimize the part the remote routers play in the update and query process and will increase the stability and scalability of this network. IP summary-address EIGRP EIGRP stub connected on all outbound interfaces to remotes on all remote routers C, D, and E

81 Hierarchy/Addressing
Permits maximum information hiding Advertise major net or default route to regions or remotes Provides adequate redundancy

82 EIGRP Scalability EIGRP is a very scalable routing protocol if proper design methods are used: Good allocation of address space Each region should have an unique address space so route summarization is possible Have a tiered network design model (Core, Distribution, Access)

83 EIGRP Scalability Use of EIGRP Stub command if possible
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 Avoid blind mutual redistribution between two routing protocols or two EIGRP processes

84 Summarized Routes Possible Stub
Tiered Network Design Summarized Routes Summarized Routes Other Regions Other Regions Core Other Regions Summarized Routes Summarized Routes Distribution Layer Other Regions Summarized Routes Possible stub Summarized Routes Possible Stub Access Layer

85 Nonscalable Network Core Bad addressing scheme Queries not bounded
Bad addressing scheme Subnets are everywhere throughout entire network Queries not bounded

86 Scalable Network Core 1.0.0.0 3.0.0.0 2.0.0.0 Readdress network
Readdress network Each region has its own block of address Queries bounded by using “ip summary-address EIGRP” command

87 Summary Query range EIGRP is not plug and play for large networks
Best way to limit query is through route summarization and new EIGRP Stub command EIGRP is not plug and play for large networks It’s a very scalable protocol with little design requirement Optimizing EIGRP network Limiting query range Route summarization Tiered network design Use of EIGRP Stub command Sufficient network resources

88 Presentation_ID © 2004 Cisco Systems, Inc. All rights reserved. 88 88 88


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