EIGRP FOR MANAGED SERVICES
TECHNOLOGY DEPLOYMENT
SANGITA PANDYA
INTERNET TECHNOLOGIES DIVISION
DECEMBER 2004
Session Number
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
1
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
VPN for Many Managed Services
V i r t u a l
P r i v a t e
MANAGED
Routing
MANAGED Security
MANAGED
CPE
MANAGED
Internet Gateway
N e t w o r k
MANAGED
IPT
Service Provider
Converged Network
Service Level
Agreement for
MANAGED Services
MANAGED
Extranet
VM
VM
VPN B
Customer
Branch
Presentation_ID
Customer HQ
© 2004 Cisco Systems, Inc. All rights reserved.
3
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
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
EIGRP AS-1
4
Cisco
Exclusive
Robust EIGRP Support
Cisco IOS Supports the Industry’s Most Comprehensive and
Robust Routing Protocol Support: RIP, OSPF, BGP, ISIS,
Including EIGRP
VPN C/Site 2
CEA2
CE1B1
12.1/16
CEB2
Static
RIPv2
16.2/16
RIPv2
P1
PE2
VPN B/Site 2
BGP
RIPv2
PE1
P2
CEA3
OSPF
OSPF
CEA1
16.2/16
P3
BGP
PE3
VPN A/Site 2
CEB3
VPN A/Site 1
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
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
5
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)
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
6
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
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
7
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
Presentation_ID
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8
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 = 10000000/Bandwidth
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
9
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
Presentation_ID
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10
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
Presentation_ID
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11
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
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
12
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
Presentation_ID
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13
EIGRP Neighbor Relationship
• Two routers become neighbors when they see each
other’s hello packet
Hello address = 224.0.0.10
• 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
Presentation_ID
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14
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
Presentation_ID
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15
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)
Presentation_ID
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16
Discovering Routes
B
A
1
afadjfjorqpoeru
39547439070713
Hello
Presentation_ID
I am Router A, Who Is on the Link?
© 2004 Cisco Systems, Inc. All rights reserved.
17
Discovering Routes
B
A
1
afadjfjorqpoeru
39547439070713
Hello
I am Router A, Who Is on the Link?
afadjfjorqpoeru
39547439070713
Here Is My Routing Information (Unicast)
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
Update
2
18
Discovering Routes
B
A
afadjfjorqpoeru
39547439070713
1
Hello
I am Router A, Who Is on the Link?
afadjfjorqpoeru
39547439070713
Here Is My Routing Information (Unicast)
Update
2
afadjfjorqpoeru
39547439070713
3
Presentation_ID
Ack
Thanks for the Information!
© 2004 Cisco Systems, Inc. All rights reserved.
19
Discovering Routes
B
A
afadjfjorqpoeru
39547439070713
1
Hello
I am Router A, Who Is on the Link?
afadjfjorqpoeru
39547439070713
Here Is My Routing Information (Unicast)
Update
2
afadjfjorqpoeru
39547439070713
4
Topology
Table
Presentation_ID
3
Ack
Thanks for the Information!
© 2004 Cisco Systems, Inc. All rights reserved.
20
Discovering Routes
B
A
afadjfjorqpoeru
39547439070713
1
Hello
I am Router A, Who Is on the Link?
afadjfjorqpoeru
39547439070713
Here Is My Routing Information (Unicast)
Update
2
afadjfjorqpoeru
39547439070713
4
Topology
Table
3
5
Ack
afadjfjorqpoeru
39547439070713
Update
Presentation_ID
Thanks for the Information!
Here Is My Route Information (Unicast)
© 2004 Cisco Systems, Inc. All rights reserved.
21
Discovering Routes
B
A
afadjfjorqpoeru
39547439070713
1
Hello
I am Router A, Who Is on the Link?
afadjfjorqpoeru
39547439070713
Here Is My Routing Information (Unicast)
2
Update
afadjfjorqpoeru
39547439070713
4
Topology
Table
3
5
Ack
Thanks for the Information!
afadjfjorqpoeru
39547439070713
Update
Here Is My Route Information (Unicast)
afadjfjorqpoeru
39547439070713
Thanks for the Information!
Ack
6
Converged
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
22
Agenda
• Fundamentals of EIGRP
• DUAL
• Summarization and Load Balancing
• Query Process
• Deployment Guidelines with EIGRP
• Summary
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
23
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
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
24
EIGRP Feasible Distance (FD)
• Feasible distance is the minimum distance (metric)
along a path to a destination network
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
25
Feasible Distance Example
Network 7
(20)
A
(100)
H
(100)
B
FDDI
C
(100)
D
E
F
Presentation_ID
G
(1)
(100)
(20)
(10)
Feasible Distance (FD)
Neighbor
7
100+20+10=130
H
7
100+1+10+10=121
B
7
100+100+20+10+10=240
D
Destination
Topology
Table
(10)
© 2004 Cisco Systems, Inc. All rights reserved.
26
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
Presentation_ID
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27
Reported Distance Example
Network 7
(20)
(100)
H
A
Topology
Table
Presentation_ID
G
(1)
(100)
(100)
(10)
B
FDDI
C
D
E
F
(100)
(20)
(10)
Reported Distance (RD)
Neighbor
7
20+10=30
H
7
1+10+10=21
B
7
100+20+10+10=140
D
Destination
© 2004 Cisco Systems, Inc. All rights reserved.
28
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
Presentation_ID
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29
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)
Presentation_ID
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30
EIGRP Feasible Successor (FS)
• A feasible successor is a neighbor whose reported
distance (RD) is less than the feasible distance (FD)
Presentation_ID
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31
Successor Example
Network 7
(100)
(20)
H
A
Topology
Table
•
•
FDDI
B
D
G
(1)
(100)
(100)
(10)
(100)
E
C
(20)
F
(10)
Destination
FD
RD
Neighbor
7
130
30
H
7
121
21
B
7
240
140
D
Router A’s
Routing Table
7 121 B
B is current successor (FD = 121)
H is the feasible successor (30 < 121)
Presentation_ID
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32
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
Presentation_ID
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33
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
Presentation_ID
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34
DUAL: Local Computation
(10)
H
#2
#1
#8
(10)
#7
#7
.
.
.
Presentation_ID
121/21 B
130/30 H
.
.
.
G
(20)
A
B
#3
X
FDDI
D
E
(100)
.
.
.
© 2004 Cisco Systems, Inc. All rights reserved.
#6
C
(1)
#4
(100)
#7
#5
F
(10)
(20)
35
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
Presentation_ID
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36
DUAL: Diffused Computation
(10)
H
#2
#1
A
.
.
.
Presentation_ID
121/21 B
130/30 H
.
.
.
FDDI
(1)
D
© 2004 Cisco Systems, Inc. All rights reserved.
#6
C
#3
(100)
.
.
.
G
(20)
B
(10)
#7
#7
X
X
#8
#7
#4
(100)
E
#5
F
(10)
(20)
37
DUAL Example
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)
A
(1)
(1)
X
B
(2)
C
Presentation_ID
(2)
D
(1)
(1)
© 2004 Cisco Systems, Inc. All rights reserved.
E
D EIGRP Topology
(a)
Cost (2) (fd)
via B
Cost (2/1) (Successor)
via C
Cost (5/3)
E EIGRP Topology
(a)
Cost (3) (fd)
via D
Cost (3/2) (Successor)
via C
Cost (4/3)
38
DUAL Example
C EIGRP Topology
(a)
Cost (3) (fd)
via B
Cost (3/1) (Successor)
via D
via E
Cost (4/3)
(a)
A
(1)
B
D
(2)
C
Presentation_ID
(2)
Q
(1)
Q
(1)
© 2004 Cisco Systems, Inc. All rights reserved.
E
D EIGRP Topology
(a) **ACTIVE** Cost (-1) (fd)
via E
(q)
via C
Cost (5/3) (q)
E EIGRP Topology
(a)
Cost (3) (fd)
via D
Cost (3/2) (Successor)
via C
Cost (4/3)
39
DUAL Example
C EIGRP Topology
(a)
Cost (3) (fd)
via B
Cost (3/1) (Successor)
via D
via E
(a)
A
(1)
B
D
(2)
(2)
R
(1)
(1)
C
Q
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
E
D EIGRP Topology
(a) **ACTIVE** Cost (-1) (fd)
via E
(q)
via C
Cost (5/3)
E EIGRP Topology
(a) **ACTIVE** Cost (-1) (fd)
via D
via C
Cost (4/3) (q)
40
DUAL Example
C EIGRP Topology
(a)
Cost (3) (fd)
via B
Cost (3/1) (Successor)
via D
via E
(a)
A
(1)
B
D
(2)
C
(2)
(1)
(1)
E
R
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
D EIGRP Topology
(a) **ACTIVE** Cost (-1) (fd)
via E
(q)
via C
Cost (5/3)
E EIGRP Topology
(a)
Cost (4) (fd)
via C
Cost (4/3) (Successor)
via D
41
DUAL Example
C EIGRP Topology
(a)
Cost (3) (fd)
via B
Cost (3/1) (Successor)
via D
via E
(a)
A
(1)
B
D
D EIGRP Topology
(a)
Cost (5) (fd)
via C
Cost (5/3) (Successor)
via E
Cost (5/4) (Successor)
R
(2)
C
Presentation_ID
(2)
(1)
(1)
© 2004 Cisco Systems, Inc. All rights reserved.
E
E EIGRP Topology
(a)
Cost (4) (fd)
via C
Cost (4/3) (Successor)
via D
42
DUAL Example
C EIGRP Topology
(a)
Cost (3) (fd)
via B
Cost (3/1) (Successor)
via D
via E
(a)
A
(1)
B
D
(2)
C
Presentation_ID
(2)
(1)
(1)
© 2004 Cisco Systems, Inc. All rights reserved.
E
D EIGRP Topology
(a)
Cost (5) (fd)
via C
Cost (5/3) (Successor)
via E
Cost (5/4) (Successor)
E EIGRP Topology
(a)
Cost (4) (fd)
via C
Cost (4/3) (Successor)
via D
43
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
Presentation_ID
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46
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
Presentation_ID
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47
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
Presentation_ID
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48
EIGRP Reliable Transport Protocol
• Per neighbor, retransmission limit is 16
• Neighbor relationship is reset when retry limit
(limit = 16) for reliable packets is reached
Presentation_ID
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49
Agenda
• Fundamentals of EIGRP
• DUAL
• SUMMARIZATION AND LOAD BALANCING
• Query Process
• Deployment Guidelines with EIGRP
• Summary
Presentation_ID
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50
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
192.168.2.x
192.168.1.x
192.168.1.0
Presentation_ID
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51
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
Presentation_ID
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52
EIGRP Summarization
• Manual summarization command:
ip summary-address EIGRP <as number> <address> <mask>
192.168.9.X
AS 1
192.168.8.0/22
192.168.8.X
192.168.10.X
Presentation_ID
S0
interface s0
ip address 192.168.11.1 255.255.255.252
ip summary-address EIGRP 1 192.168.8.0 255.255.252.0
© 2004 Cisco Systems, Inc. All rights reserved.
53
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>
Presentation_ID
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54
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
Presentation_ID
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55
Variance Example
B
E
20
10
Variance 2
10
C
20
A
10
Net X
25
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
Presentation_ID
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56
Agenda
• Fundamentals of EIGRP
• DUAL
• Summarization and Load Balancing
• QUERY PROCESS
• Deployment Guidelines with EIGRP
• Summary
Presentation_ID
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57
EIGRP Query Process
• EIGRP is Advanced
Distant Vector—it relies
on its neighbor to
provide routing
information
Have You Seen My Sparky?
• 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
Presentation_ID
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58
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
Presentation_ID
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59
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
Presentation_ID
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60
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
Query for X
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
AS 1
Reply for X
Query for X
61
EIGRP Query Range
• Summarization point
Auto or manual summarization bound queries
Requires a good address allocation scheme
B Summarizes 130.0.0.0/8 to A
A
B
129.x.x.x
C
X
130.130.1.0/24
130.x.x.x
Query for
130.130.1.0/24
Reply with Infinity and the
Query Stops Here!
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
Query for
130.130.1.0/24
62
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
Presentation_ID
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63
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
Presentation_ID
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64
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
Presentation_ID
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65
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)
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
66
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
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
67
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:
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
68
CE-PE Connectivity
• Things an enterprise customers needs to consider:
• Things a Service Providers need to consider:
• Topology Ex:
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
69
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
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
70
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
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
71
Limiting Updates/Queries—Example
Distribution Layer
Remote Sites
10.1.8.0/24
RTRC
RTRB
RTRD
RTRA
RTRE
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© 2004 Cisco Systems, Inc. All rights reserved.
72
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
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
73
Limiting Updates/Queries—Example
Distribution Layer
Queries
Replies
Remote Sites
X
10.1.8.0/24
RTRC
RTRB
RTRD
RTRA
RTRE
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
74
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
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
75
Limiting Updates/Queries—Better
Distribution Layer
Queries
Replies
Remote Sites
X
10.1.8.0/24
RTRC
RTRB
RTRD
RTRA
IP summary-address EIGRP 1 10.0.0.0 255.0.0.0
on all outbound interfaces to remotes
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
RTRE
76
Limiting Updates/Queries—Summary
• Convergence simplified by adding the
summary-address statements
• Remote routers just reply when queried
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
77
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
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
78
Limiting Updates/Queries—Best
• Best practice is to combine Summarization and
EIGRP STUB command
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
79
Limiting Updates/Queries—Best
Distribution Layer
Remote Sites
10.1.8.0/24
Queries
Replies
X
RTRC
RTRB
RTRD
RTRA
RTRE
IP summary-address EIGRP 1 10.0.0.0 255.0.0.0
on all outbound interfaces to remotes
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
EIGRP stub connected
on all remote routers C, D, and E
80
Hierarchy/Addressing
• Permits maximum information hiding
• Advertise major net or default route to regions
or remotes
• Provides adequate redundancy
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
81
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)
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
82
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
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
83
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
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
84
Nonscalable Network
Core
1.1.1.0
1.1.2.0
2.2.3.0
3.3.4.0
2.2.1.0
3.3.2.0
3.3.3.0
1.1.4.0
3.3.1.0
2.2.2.0
1.1.3.0
2.2.1.0
1.1.1.0 3.3.4.0
Token
Ring
1.1.2.0
Token
Ring
3.3.1.0
Token
Ring
1.1.3.0
2.2.3.0
Token
Ring
1.1.4.0
Token
Ring
Token
Ring
3.3.4.0
3.3.3.0
2.2.2.0
• Bad addressing scheme
Subnets are everywhere throughout entire network
• Queries not bounded
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
85
Scalable Network
Core
1.0.0.0
3.0.0.0
2.0.0.0
3.3.1.0
1.1.1.0 1.1.4.0
Token
Ring
1.1.2.0
Token
Ring
Token
Ring
2.2.1.0
2.2.3.0
1.1.3.0
Token
Ring
3.3.4.0
Token
Ring
Token
Ring
3.3.4.0
3.3.3.0
2.2.2.0
• Readdress network
Each region has its own block of address
• Queries bounded by using “ip summary-address EIGRP” command
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
86
Summary
• Query range
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
Presentation_ID
© 2004 Cisco Systems, Inc. All rights reserved.
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88