11-19-2013 10:21 PM - edited 03-01-2019 04:59 PM
This document describes how the eigrp summary route metrics is determined.
There is a need to provide information on how the summary route metrics, which is created by the ip summary-address eigrp command, is determined and details of the summary-metric command implemented in association with the command.
1. Configuration
----------------------------------------------------------------------------
On R2, configure settings to summarize routes to 10.1.0.0/16 on the interface which connected to the R3
ip summary-address eigrp 1 10.1.0.0 255.255.0.0
(All setting examples are described at the end of this document)
(10.1.1.0/24)--1M--+
(10.1.2.0/24)-64K-[R1]-(10.12.1.0/24)-[R2]-(172.20.23/24)-[R3]
(10.1.3.0/24)-10M--+
(※ 15.1(4)M3 is used for all the output examples below)
----------------------------------------------------------------------------
2. How the summary route metric is determined
For EIGRP, the smallest metric among the component routes (routes contained in the summary) will be employed as the summary route metric.
----------------------------------------------------------------------------
R2#show ip eigrp topology
EIGRP-IPv4 Topology Table for AS(1)/ID(172.20.1.2)
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status
P 172.20.1.0/24, 1 successors, FD is 281600
via Connected, Ethernet1/0
P 10.12.1.0/24, 1 successors, FD is 281600
via Connected, Ethernet0/0
P 10.1.3.0/24, 1 successors, FD is 307200
via 10.12.1.1 (307200/281600), Ethernet0/0
P 10.1.0.0/16, 1 successors, FD is 307200
via Summary (307200/0), Null0 <-- 307200, the smallest value among the component routes
P 10.1.2.0/24, 1 successors, FD is 40051200
via 10.12.1.1 (40051200/40025600), Ethernet0/0
P 10.1.1.0/24, 1 successors, FD is 2611200
via 10.12.1.1 (2611200/2585600), Ethernet0/0
R2#
----------------------------------------------------------------------------
If a component route is updated and the smallest metric is changed, the summary route metric is also updated.
If there are multiple metric values in a component route, care should be exercised during network design.
----------------------------------------------------------------------------
Example: If 10.1.3.0/24 with the smallest metric goes down
R2#debug ip eigrp summary
EIGRP-IPv4 Summary debugging is on
R2#
06:41:46.167: EIGRP-IPv4(1): summary_depend: dest 10.1.3.0/24 vec 0, metric 307200, add 0 auto 0
06:41:46.167: EIGRP-IPv4(1): summary_depend: revise summary 10.1.0.0/16
06:41:46.167: EIGRP-IPv4(1): summary_revise: result 2
06:41:46.167: EIGRP-IPv4(1): summary_enqueue: 10.1.0.0/16 vec(0) summary changed
06:41:46.167: EIGRP-IPv4(1): summary_depend: dest 10.1.3.0/24 vec 0, metric 0, add 0 auto 0
06:41:46.167: EIGRP-IPv4(1): summary_depend: revise summary 10.1.0.0/16
06:41:46.167: EIGRP-IPv4(1): summary_revise: result 2
06:41:46.167: EIGRP-IPv4(1): summary_process: 3 components with static metric(0)
06:41:46.167: EIGRP-IPv4(1): summary_metric_calc: 10.1.0.0/16 with 3 components and metric 307200
06:41:46.167: EIGRP-IPv4(1): summary_metric overlapping: 10.1.2.0/24 metric 40051200
06:41:46.167: EIGRP-IPv4(1): summary_metric overlapping: 10.1.1.0/24 metric 2611200
06:41:46.167: EIGRP-IPv4(1): summary_metric_calc: 10.1.0.0/16, from 10.1.1.0/24, metric 2611200
06:41:46.167: EIGRP-IPv4(1): summary_process: 10.1.0.0/16 old(307200) new(2611200) processed(yes)
06:41:46.355: EIGRP-IPv4(1): summary_depend: dest 10.1.3.0/24 vec 0, metric 0, add 0 auto 0
06:41:46.355: EIGRP-IPv4(1): summary_depend: revise summary 10.1.0.0/16
06:41:46.355: EIGRP-IPv4(1): summary_revise: result 2
06:41:46.355: EIGRP-IPv4(1): summary_enqueue: 10.1.0.0/16 vec(0) summary changed
06:41:46.355: EIGRP-IPv4(1): summary_decr: 10.1.0.0/16 count(2)
06:41:46.355: EIGRP-IPv4(1): summary_process: 2 components with static metric(0)
06:41:46.355: EIGRP-IPv4(1): summary_metric_calc: 10.1.0.0/16 with 2 components and metric 2611200
06:41:46.355: EIGRP-IPv4(1): summary_metric overlapping: 10.1.2.0/24 metric 40051200
06:41:46.355: EIGRP-IPv4(1): summary_metric overlapping: 10.1.1.0/24 metric 2611200
06:41:46.355: EIGRP-IPv4(1): summary_metric_calc: 10.1.0.0/16, from 10.1.1.0/24, metric 2611200
06:41:46.355: EIGRP-IPv4(1): summary_process: 10.1.0.0/16 old(2611200) new(2611200) processed(yes)
R2#
R2#show ip eigrp topology
EIGRP-IPv4 Topology Table for AS(1)/ID(172.20.1.2)
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status
P 172.20.1.0/24, 1 successors, FD is 281600
via Connected, Ethernet1/0
P 10.12.1.0/24, 1 successors, FD is 281600
via Connected, Ethernet0/0
P 10.1.0.0/16, 1 successors, FD is 307200
via Summary (2611200/0), Null0 <-- 2611200, the smallest value among the component routes
P 10.1.2.0/24, 1 successors, FD is 40051200
via 10.12.1.1 (40051200/40025600), Ethernet0/0
P 10.1.1.0/24, 1 successors, FD is 2611200
via 10.12.1.1 (2611200/2585600), Ethernet0/0
R2#
----------------------------------------------------------------------------
3. Using the summary-metric command
If there are many component routes to be summarized and the component routes are frequently updated, the metrics are also updated frequently, and thus a high CPU state may be caused depending on the configuration.
To deal with such a situation, the summary-metric command was implemented.
This command has been implemented in 12.2(33)SRE, 12.2(33)SXJ, 12.2(33)XNE/2.5.0, 15.0(1)M, 15.1(1)SG or later.
This command explicitly sets the metric for the summary regardless of the component route metric.
----------------------------------------------------------------------------
R2#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R2(config)#router eigrp 1
R2(config-router)#summary-metric 10.1.0.0/16 10000 200 255 0 1500
09:09:26.023: EIGRP-IPv4(1): summary metric cmd for 10.1.0.0/16
09:09:26.023: EIGRP-IPv4(1): summary metric dly(51200) bw(256000) r(255), l(0), mtu(1500) dist(5)
09:09:26.023: EIGRP-IPv4(1): summary_update - summary changed
09:09:26.023: EIGRP-IPv4(1): summary_enqueue: 10.1.0.0/16 vec(0) summary changed
09:09:26.039: EIGRP-IPv4(1): summary_process: 2 components with static metric(1)
09:09:26.039: EIGRP-IPv4(1): summary_process: 10.1.0.0/16 old(4294967295) new(307200) processed(yes)
R2(config-router)#end
R2#
R2#show ip eigrp topology
EIGRP-IPv4 Topology Table for AS(1)/ID(172.20.1.2)
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status
P 172.20.1.0/24, 1 successors, FD is 281600
via Connected, Ethernet1/0
P 10.12.1.0/24, 1 successors, FD is 281600
via Connected, Ethernet0/0
P 10.1.0.0/16, 1 successors, FD is 307200
via Summary (307200/0), Null0 <-- 307200, regardless of the component route value
P 10.1.2.0/24, 1 successors, FD is 40051200
via 10.12.1.1 (40051200/40025600), Ethernet0/0
P 10.1.1.0/24, 1 successors, FD is 2611200
via 10.12.1.1 (2611200/2585600), Ethernet0/0
R2#
----------------------------------------------------------------------------
4. All Devices Settings
----------------------------------------------------------------------------
!
hostname R1
!
interface Ethernet0/0
ip address 10.12.1.1 255.255.255.0
!
interface Ethernet1/0
bandwidth 1000
ip address 10.1.1.1 255.255.255.0
!
interface Ethernet2/0
bandwidth 64
ip address 10.1.2.1 255.255.255.0
!
interface Ethernet3/0
bandwidth 10000
ip address 10.1.3.1 255.255.255.0
!
router eigrp 1
network 10.0.0.0
!
----------------------------------------------------------------------------
!
hostname R2
!
interface Ethernet0/0
ip address 10.12.1.2 255.255.255.0
!
interface Ethernet1/0
ip address 172.20.1.2 255.255.255.0
ip summary-address eigrp 1 10.1.0.0 255.255.0.0
!
router eigrp 1
summary-metric 10.1.0.0/16 10000 200 255 0 1500
network 10.0.0.0
network 172.20.0.0
!
----------------------------------------------------------------------------
!
hostname R3
!
interface Ethernet1/0
ip address 172.20.1.3 255.255.255.0
!
router eigrp 1
network 172.20.0.0
!
----------------------------------------------------------------------------
Original Document: Cisco Support Community Japan DOC-26447
Author: Tsuyoshi Niitani
Posted on August 13, 2012
Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community: