EIGRP Configuration
This breadth explains the majority of the options for EIGRP configuration. The “Foundation Summary”
section includes the abounding syntax of the commands, forth with some comments, in Table 8-6.
EIGRP Agreement Example
Example 8-6 lists the agreement for R1, R2, R4, and R5 from Figure 8-4. The routers were
configured based on the afterward architecture goals:
■ Accredit EIGRP on all interfaces.
EIGRP Agreement 223
■ Configure K ethics to avoid bandwidth.
■ Configure R5 as an EIGRP butt router.
■ Ensure that R2’s LAN interface uses a Accost and Authority time of 2 and 6, respectively.
■ Configure R4 to acquiesce 75 percent of interface bandwidth for EIGRP updates.
■ Acquaint R4’s LAN subnet, but do not attack to accelerate or accept EIGRP updates on the LAN.
Example 8-6 Basic EIGRP Agreement on R1, R2, R4, and R5
! Below, R1 EIGRP-related configuration
! The absence metric weights are “0 1 0 1 0 0”.
router eigrp 1
network 172.31.0.0
metric weights 0 0 0 1 0 0
! R2 EIGRP-related configuration
! Agenda the commands acclimated to change the Accost and Authority Time ethics per interface.
! R2’s Hellos acquaint the timer values, and added routers on the LAN use these
! ethics on their acquaintance accord with R2. Additionally below, agenda the use of the
! afflicted affectation to bout a subset of interfaces on a distinct arrangement command.
interface FastEthernet0/0
ip hello-interval eigrp 1 2
ip hold-time eigrp 1 6
!
router eigrp 1
network 10.0.0.0
network 172.31.11.2 0.0.0.0
network 172.31.24.0 0.0.1.255
metric weights 0 0 0 1 0 0
! R4 EIGRP-related configuration
! Below, the allotment of the interface bandwidth acclimated for EIGRP is changed. The
! amount can go over 100% to acquiesce for cases in which the bandwidth has
! been artificially bargain to appulse the EIGRP metric. Additionally agenda that R4 makes
! its e0/0 interface passive, acceptation no routes abstruse or advertised on E0/0.
interface Serial0/0.1 point-to-point
bandwidth 64
ip bandwidth-percent eigrp 1 150
!
router eigrp 1
passive-interface Ethernet0/0
network 172.31.0.0
metric weights 0 0 0 1 0 0
! R5 EIGRP-related configuration
! Below, agenda R5’s agreement as a butt area.
continues
224 Chapter 8: EIGRP
EIGRP allows for bigger ascendancy of the three functions enabled on an interface by the EIGRP
network command. (The three functions are announcement the affiliated subnet, sending routing
updates, and accepting acquisition updates.) Like OSPF, the EIGRP arrangement command supports
configuration of an alternative wildcard affectation (as apparent on R4 in Example 8-6), acceptance each
interface to be akin individually—and authoritative it simple to accredit EIGRP on a subset of
interfaces. Also, a LAN subnet ability accept a distinct router absorbed to it, so there is no charge to
attempt to accelerate or accept updates on those interfaces. By enabling EIGRP on the interface with a
network command, and again configuring the passive-interface command, you can stop the router
from sending Hellos. If a router does not accelerate Hellos, it forms no acquaintance adjacencies, and it then
neither sends nor receives updates on that LAN.
Example 8-6 additionally shows R5 configured as an EIGRP butt router. R5 announces itself as a stub
router via its EIGRP Hellos. As a result, R2 will not accelerate Concern letters to R5, attached the scope
of Concern messages.
The eigrp butt command has several options, with the absence options (connected and summary)
shown on the aftermost band of Example 8-6. (Note that the eigrp butt command was typed, and IOS
added the affiliated and arbitrary options in the configuration.) Table 8-4 lists the eigrp stub
command options, and explains some of the argumentation abaft application them.
Note that the butt advantage still requires the butt router to anatomy acquaintance relationships, alike in
receive-only mode. The butt router artlessly performs beneath assignment and reduces the concern scope.
Example 8-6 additionally shows the EIGRP accost breach and authority time actuality set. These ambit can
be set per interface application the interface subcommands ip hello-interval eigrp asn abnormal and
router eigrp 1
network 172.31.0.0
metric weights 0 0 0 1 0 0
eigrp butt affiliated summary
Table 8-4 Options on the eigrp butt Command
Option This Router Is Accustomed To…
connected Acquaint affiliated routes, but alone for interfaces akin with a network
command.
summary Acquaint auto-summarized or statically configured arbitrary routes.
static Acquaint changeless routes, bold the redistribute changeless command is configured.
redistributed Acquaint redistributed routes, bold redistribution is configured.
receive-only Not acquaint any routes. This advantage cannot be acclimated with any added option.
Example 8-6 Basic EIGRP Agreement on R1, R2, R4, and R5 (Continued)
EIGRP Agreement 225
ip hold-time eigrp asn seconds, respectively. The absence EIGRP accost breach defaults to 5
seconds on best interfaces, with NBMA interfaces whose bandwidth is T1 or slower application a hello
interval of 60 seconds. The authority time defaults to 15 and 180 seconds, respectively—three times
the absence accost interval. However, if you change the accost interval, the authority time absence does not
automatically change to three times the new accost interval; instead, it charcoal at 15 or 180 seconds.
EIGRP Amount Balancing
EIGRP allows for up to six equal-metric routes to be installed into the IP acquisition table at the same
time. However, because of the circuitous EIGRP metric calculation, metrics may generally be abutting to
each other, but not absolutely equal. To acquiesce for metrics that are somewhat abutting in amount to be
considered equal, and added to the IP acquisition table, you can use the about-face multiplier command.
The multiplier defines a amount that is assorted by the everyman metric (in added words, the FD,
which is the metric of the almsman route). If any added routes accept a bigger metric than that
product of about-face * FD, those added routes are advised equal, and added to the acquisition table.
Once the assorted routes for the aforementioned destination are in the acquisition table, EIGRP allows several
options for acclimation cartage beyond the routes. Table 8-5 summarizes the commands that impact
how amount acclimation is done with EIGRP, additional the added commands accompanying to installing multiple
EIGRP routes into the aforementioned subnet. Agenda that these commands are all subcommands beneath router
eigrp.
NOTE EIGRP allows alone FS routes to be advised for accession as a aftereffect of application the
variance command. Otherwise, acquisition loops could occur.
Table 8-5 EIGRP Avenue Load-Balancing Commands
Router EIGRP
Subcommand Meaning
variance Any FS avenue whose metric is beneath than the about-face amount assorted by the
FD is added to the acquisition table (within the restrictions of the maximumpaths
command).
maximum-paths {1..6} The best cardinal of routes to the aforementioned destination accustomed in the routing
table. Defaults to 4.
traffic-share counterbalanced The router balances beyond the routes, giving added packets to lower-metric routes.
traffic-share min Although assorted routes are installed, sends cartage application alone the lowestmetric
route.
traffic-share balanced
across-interfaces
If added routes abide than are accustomed with the maximum-paths setting, the
router chooses routes with altered approachable interfaces, for bigger balancing.
No traffic-share
command configured
Balances analogously beyond routes, blank EIGRP metrics.