From: Brian McGahan (brian@cyscoexpert.com)
Date: Sat Sep 07 2002 - 14:33:16 GMT-3
Peng,
EIGRP is classless, and will therefore carry subnet mask
information. Auto-summary in EIGRP only applies when you have the
connection of two different major networks. In the case of my lab,
turning auto-summary off is not necessarily required, since the
220.x.x.x loopbacks on R1 are already classful.
Take the following example:
|
|--R1--R2
|
We have two networks, 10.1.1.0/24, and 10.12.0.0/30. R1's
Ethernet is 10.1.1.0/24, the transit link between R1 & R2 is
10.12.0.0/30. Both routers are running EIGRP 1 with auto-summary
enabled (default). Even though the subnet masks are discontiguous, R2
will still see an exact match for 10.1.1.0/24.
Now add the loopback 1.1.1.1/32 on R1. R2 will only see the
classful summary, 1.0.0.0/8.
As a general rule, you should turn auto-summary off. Any
summarization that you need to do can be manually configured.
See the following link for more detail:
http://www.cisco.com/warp/public/103/eigrp5.html
HTH
Brian McGahan, CCIE #8593
Director of Design and Implementation
brian@cyscoexpert.com
CyscoExpert Corporation
Internetwork Consulting & Training
http://www.cyscoexpert.com
Voice: 847.674.3392
Fax: 847.674.2625
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> Peng Zheng
> Sent: Saturday, September 07, 2002 10:59 AM
> To: ccielab@groupstudy.com
> Subject: eigrp in cyscoexpert sample lab
>
> Hi,
>
> In the sample lab, auto-summary is used for eigrp. I
> thought it's because /24 mask are used anywhere but
> frame relay. And R1, R2 will get the route for frame
> relay through OSPF. R2 will also redistribute that
> route with /24 mask.
>
> Is that correct?
>
> If other mask is used for R3 ethernet, Is it necessary
> to turn off auto-summary?
>
> Thank you for help.
>
> Best Wishes,
> Peng Zheng
>
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This archive was generated by hypermail 2.1.4 : Mon Oct 07 2002 - 07:43:46 GMT-3