# How to configure EIGRP Summarization
**URL:** https://forum.networklessons.com/t/how-to-configure-eigrp-summarization/886
**Category:** Lessons Discussion
**Created:** [December 22, 2016, 12:29am UTC](https://forum.networklessons.com/t/how-to-configure-eigrp-summarization/886 "2016-12-22T00:29:49Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)
#### Post date: [December 22, 2016, 12:29am UTC](https://forum.networklessons.com/t/how-to-configure-eigrp-summarization/886/1 "2016-12-22T00:29:49Z")
This topic is to discuss the following lesson:
> **[How to configure EIGRP Summarization](https://networklessons.com/eigrp/how-to-configure-eigrp-summarization)**
>
> This lesson explains and demonstrates how to configure summarization for EIGRP with the summary-route command on Cisco IOS routers.
---
### Author:  [@system](https://forum.networklessons.com/u/system)
#### Post date: [May 16, 2013, 6:31pm UTC](https://forum.networklessons.com/t/how-to-configure-eigrp-summarization/886/2 "2013-05-16T18:31:25Z")
Hello Rene,
I have a question regarding ip summary-address command in above lesson.
By applying ip aummary-address command in fastethrnet 2/0 interface,
how come heart router know about the summary address.
As my understanding ip summary address is per interface basis.
I should apply ip summary-address in fastethernet 1/0 interface.
Would you correct me and help me to understand better.
Thanks.
---
### Author:  [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)
#### Post date: [May 24, 2013, 9:43am UTC](https://forum.networklessons.com/t/how-to-configure-eigrp-summarization/886/3 "2013-05-24T09:43:19Z")
Hi Toral,
I just changed the picture because the interface number didn’t match. You configure a summary outbound on an interface facing towards your EIGRP neighbor.
Rene
---
### Author:  [@system](https://forum.networklessons.com/u/system)
#### Post date: [August 21, 2013, 11:22am UTC](https://forum.networklessons.com/t/how-to-configure-eigrp-summarization/886/4 "2013-08-21T11:22:58Z")
Simple but effective workout to understand EIGRP summerizing
---
### Author:  [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)
#### Post date: [August 28, 2013, 2:09pm UTC](https://forum.networklessons.com/t/how-to-configure-eigrp-summarization/886/5 "2013-08-28T14:09:04Z")
Thanks Django!
---
### Author:  [@system](https://forum.networklessons.com/u/system)
#### Post date: [October 11, 2013, 9:28pm UTC](https://forum.networklessons.com/t/how-to-configure-eigrp-summarization/886/6 "2013-10-11T21:28:24Z")
thanks for the nice lesson, keep up the good work
---
### Author:  [@oscaritox2000](https://forum.networklessons.com/u/oscaritox2000)
#### Post date: [November 23, 2015, 10:56pm UTC](https://forum.networklessons.com/t/how-to-configure-eigrp-summarization/886/7 "2015-11-23T22:56:08Z")
Rene, why is it /23 mask? when I see the first statement showing /24.
```auto
Spade(config)#<strong>interface fastEthernet 2/0</strong>
Spade(config-if)#<strong>ip summary-address eigrp 1 172.16.0.0 255.255.254.0</strong>
```
1st. statement.
```auto
Hearts#<strong>show ip route eigrp
172.16.0.0/24</strong> is subnetted, 2 subnets
D <strong>172.16.0.0</strong> [90/30720] via 192.168.12.1, 00:02:28, FastEthernet0/0
D <strong>172.16.1.0</strong> [90/30720] via 192.168.12.1, 00:02:28, FastEthernet0/0
```
Is it to cover 172.16. **1**.0 ?
Thanks,
Oscar
---
### Author:  [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)
#### Post date: [November 24, 2015, 1:22pm UTC](https://forum.networklessons.com/t/how-to-configure-eigrp-summarization/886/8 "2015-11-24T13:22:51Z")
Hi Oscar,
That’s right, 172.16.0.0/23 covers both 172.16.0.0/24 and 172.16.1.0/24.
Rene
---
### Author:  [@ethel\_13mx](https://forum.networklessons.com/u/ethel_13mx)
#### Post date: [December 1, 2015, 6:39pm UTC](https://forum.networklessons.com/t/how-to-configure-eigrp-summarization/886/9 "2015-12-01T18:39:39Z")
Hello Rene,
Can you show us more examples using summarization? it’s an easy topic but I would like to see another scenarios 🙂
Thanks!!!
---
### Author:  [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)
#### Post date: [December 3, 2015, 2:14pm UTC](https://forum.networklessons.com/t/how-to-configure-eigrp-summarization/886/10 "2015-12-03T14:14:48Z")
Hi Diana,
Sure, anything particular you would like to see?
Rene
---
### Author:  [@azaadafghan](https://forum.networklessons.com/u/azaadafghan)
#### Post date: [February 8, 2016, 1:14am UTC](https://forum.networklessons.com/t/how-to-configure-eigrp-summarization/886/11 "2016-02-08T01:14:05Z")
Hey Rene,
I am alittle confused with summarization over here. So taking your example over here, when we want to summarize subnets we used /23 subnet mask that is shared by all the subnets that we want to summarize and use it on interface level. But in your next lesson “no auto summarization” when we disable the “no auto summarization” we use wild card mask under eigrp configuration, what is the difference, why didn’t we use wild card mask over here ?
Best,
Tooryalai
---
### Author:  [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)
#### Post date: [February 9, 2016, 5:34pm UTC](https://forum.networklessons.com/t/how-to-configure-eigrp-summarization/886/12 "2016-02-09T17:34:21Z")
Hi Tooryalai,
This can be confusing yes. Cisco isn’t very consistent with their usage of wildcards, subnet masks and CIDR notation. Sometimes it doesn’t make much sense 🙂
Rene
---
### Author:  [@purohit.am](https://forum.networklessons.com/u/purohit.am)
#### Post date: [September 11, 2016, 5:08am UTC](https://forum.networklessons.com/t/how-to-configure-eigrp-summarization/886/13 "2016-09-11T05:08:49Z")
Hi Rene,
I have a doubt , how does summarization prevents the SIA issue ?
or in other words how does the neighbor knows not to send the query packet to this neighbor which is summarizing addresses to me !
thanks,
---
### Author:  [@andrew](https://forum.networklessons.com/u/andrew)
#### Post date: [September 13, 2016, 7:02pm UTC](https://forum.networklessons.com/t/how-to-configure-eigrp-summarization/886/14 "2016-09-13T19:02:30Z")
Amit,
Only on the router where the summarization is configured does the Query process stop–not on the router that originates the Query. So for example, if you have three routers A, B, and C with a topology of A—B—C. B has created a summary, say 10.10.0.0/16. Suppose Router A has a route 10.10.10.0/24 that goes active. Router A will still send the Query message to B, but B will see that 10.10.10.0/24 is contained within its own configured summary of 10.10.0.0/16. This will cause Router B to stop propagation of the Query to router C. Additionally, Router B will reply immediately back to A’s Query saying “Unreachable”
---
### Author:  [@ryllise1234](https://forum.networklessons.com/u/ryllise1234)
#### Post date: [October 31, 2016, 3:31am UTC](https://forum.networklessons.com/t/how-to-configure-eigrp-summarization/886/15 "2016-10-31T03:31:56Z")
Hey,
Has anyone tested this in GNS3?
Can’t seem to get it working
```
R1
interface Loopback0
ip address 192.168.1.1 255.255.255.0
!
interface Loopback1
ip address 192.168.2.1 255.255.255.0
!
interface FastEthernet0/0
ip address 1.1.1.1 255.255.255.252
ip summary-address eigrp 1 192.168.0.0 255.255.252.0 5
duplex auto
speed auto
router eigrp 1
network 1.1.1.0 0.0.0.3
no auto-summary
```
-
```
R2
interface FastEthernet0/0
ip address 1.1.1.2 255.255.255.252
duplex auto
speed auto
router eigrp 1
network 1.1.1.0 0.0.0.3
no auto-summary
R2#show ip route
1.0.0.0/30 is subnetted, 1 subnets
C 1.1.1.0 is directly connected, FastEthernet0/0
R2#
```
---
### Author:  [@lagapidis](https://forum.networklessons.com/u/lagapidis)
#### Post date: [November 13, 2016, 5:26pm UTC](https://forum.networklessons.com/t/how-to-configure-eigrp-summarization/886/16 "2016-11-13T17:26:01Z")
Hello Ryan
I notice that in your show IP route command, no EIRGP routes show up. This tells me that for some reason, no EIGRP neighbours have been created. You should at least see the 192.168.1.0 and 192.168.2.0 subnets separately show up. Check the neighbour table to see that they have successfully created an adjacancy. Before you configure any EIGRP summarization, try to get EIGRP alone to function correctly. Then you can add the summarization commands.
I hope this has been helpful.
Laz
---
### Author:  [@hamasferrer](https://forum.networklessons.com/u/hamasferrer)
#### Post date: [November 14, 2016, 9:12pm UTC](https://forum.networklessons.com/t/how-to-configure-eigrp-summarization/886/17 "2016-11-14T21:12:02Z")
If the network is summarized, should not have an A.D of 5 in the neighbor routing table???
---
### Author:  [@andrew](https://forum.networklessons.com/u/andrew)
#### Post date: [November 16, 2016, 2:42am UTC](https://forum.networklessons.com/t/how-to-configure-eigrp-summarization/886/18 "2016-11-16T02:42:56Z")
Hector,
No, it should not. The Administrative Distance of 5 for an EIGRP summary route is local only on the router that does the summarizing. When that summary is then advertised to a neighbor, the neighbor installs the summary with the regular AD of 90.
---
### Author:  [@hamasferrer](https://forum.networklessons.com/u/hamasferrer)
#### Post date: [November 16, 2016, 2:09pm UTC](https://forum.networklessons.com/t/how-to-configure-eigrp-summarization/886/19 "2016-11-16T14:09:17Z")
Hi Andrew,
Then, based on the exercise, it is in R1 where the route should appear with A.D. of 5.
```
R1#show ip route eigrp
172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks
D 172.16.0.0/23 is a summary, 00:01:38, Null0
```
where we can check the A.D.?? Since it does not appear.
And thanks for ur reply 🙂
---
### Author:  [@andrew](https://forum.networklessons.com/u/andrew)
#### Post date: [November 16, 2016, 2:21pm UTC](https://forum.networklessons.com/t/how-to-configure-eigrp-summarization/886/20 "2016-11-16T14:21:39Z")
Hector,
To check the AD of the route, issue:
#show ip route 172.16.0.0 255.255.254.0
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