RE: eigrp auto-summary

Mirco -

In the documentation, says:

"Automatic summarization is performed when two or more network (EIGRP)
router configuration or address family configuration commands are configured
for the EIGRP process."

The requirement for the multiple network statements, implies directly
connected interfaces only. (Not super clear in the doc, I agree.)

Here is the link:

http://www.cisco.com/en/US/partner/docs/ios/iproute_eigrp/configuration/guid
e/ire_cfg_eigrp_ps6441_TSD_Products_Configuration_Guide_Chapter.html#wp10601
74

It is in the first paragraph, under Route Summarization.

Best wishes,

Keith

-----Original Message-----
From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
Mirco Orlandi
Sent: Wednesday, May 19, 2010 5:25 AM
To: ccielab_at_groupstudy.com
Subject: eigrp auto-summary

Hi group,
I'm analyzing eigrp auto-summary behavior with a minilab of 3 routers, and
I'm surprised about the result.

Topology:
R1[f0/0]------[f0/0]R2[f0/1]------[f0/1]R3

IP plan:
R1[Lo0]: 192.168.1.1/32
R1[f0/0]: 192.168.100.1/30
R2[Lo0]: 192.168.2.2/32
R2[f0/0]: 192.168.100.2/30
R2[f0/1]: 192.168.200.1/30
R3[Lo0]: 192.168.3.3/32
R3[f0/1]: 192.168.200.2/30

auto-summary enabled on R2, disabled on R1 and R3:

R2
router eigrp 100
 network 192.168.0.0 0.0.255.255
 auto-summary

R1, R3
router eigrp 100
 network 192.168.0.0 0.0.255.255
 no auto-summary

Looking at routing table on R3, R2:Lo0 is summarized by R2, subnet between
R1&R2 is summarized by R2, R1:Lo0 is not summarized.

     192.168.200.0/30 is subnetted, 1 subnets
C 192.168.200.0 is directly connected, FastEthernet0/1
     192.168.1.0/32 is subnetted, 1 subnets
D 192.168.1.1 [90/435200] via 192.168.200.1, 01:40:21, FastEthernet0/1
D 192.168.2.0/24 [90/409600] via 192.168.200.1, 01:40:21, FastEthernet0/1
D 192.168.100.0/24 [90/307200] via 192.168.200.1, 01:40:21,
FastEthernet0/1
     192.168.3.0/32 is subnetted, 1 subnets
C 192.168.3.3 is directly connected, Loopback0

What i see, is that R2 performs auto-summarization only for connected
network.
Can you explain why R1:Lo isn't summarized by R2, or provide a link?

Cisco-doc said: "EIGRP performs an auto-summarization each time it crosses a
border between two different major networks", but this doesn't match with
the above result.

thanx,
mirco.

Blogs and organic groups at http://www.ccie.net
Received on Wed May 19 2010 - 10:48:32 ART