network boundary

Unanswered Question
Apr 10th, 2006

can anyone define this ? I am unsure what it means with respect the eigrp !!

summarization would only occur when routes cross a network boundary

I have this problem too.
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mheusinger Mon, 04/10/2006 - 00:43


this probably refers to classful addressing (class A, B, C, ...). EIGRP will - by default - create a summary route when an update crosses a network boundary. Example with 3 routers R1, R2 and R3 running EIGRP: - R1 - - R2 - - R3

In this example R2 would anounce to R3, because the update "leaves" the network and "enters" into

You can avoid this by configuring "no auto-summary" in EIGRP.

Hope this helps! Please rate all posts.

Regards, Martin

carl_townshend Mon, 04/10/2006 - 04:23

so basically the boundary is when it changes ip say from the 10 to the 192 network ?


pkhatri Mon, 04/10/2006 - 04:36

Yes... the boundary referred to here is the old classful boundary. So if you go from a network to a network, that will not be considered a network boundary since both of those networks are part of the class B network of It has to cross classful boundaries...

So your example of going from a 10.x.x.x network to a 192.x.x.x network constitutes a case where this applies.

Pls remember to rate posts.


mheusinger Mon, 04/10/2006 - 04:38

Hello Carl,

yes a boundary would be between one classful network and another like 10/8 to 172.16/16 or to 123.123/16 and so on.

Hope this helps! Please rate all posts.

Regards, Martin

carl_townshend Mon, 04/10/2006 - 08:25

So no matter what mask you use then, unless you use the no auto summary command when it crosses boundaries it will just advertise the 10/8 network even though you might have multiple 10 /24 networks behind that router in which case it wont be able to find them ?



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Posted April 10, 2006 at 12:22 AM
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