Re: eigrp auto-summary

Thank you very much, Keith. It helps me to understand that:

- "auto-summary" works only on directly connected subnets if they are in
eigrp topology (by network command);
- "ip summary-address eigrp ..." works also on eigrp learned routes, if they
are installed in routing table.

Correct me please, if I'm wrong.
mirco

On Wed, May 19, 2010 at 7:48 PM, Keith Barker <kbarker_at_ine.com> wrote:

> 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<http://www.cisco.com/en/US/partner/docs/ios/iproute_eigrp/configuration/guid%0Ae/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 <http://192.168.2.2/32%0AR2[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 <http://192.168.3.3/32%0AR3[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.
>
>
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Received on Thu May 20 2010 - 10:39:42 ART