mheusinger Mon, 04/10/2006 - 00:43
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Hello,


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:

10.1.1.0/24 - R1 - 10.1.2.0/24 - R2 - 192.168.1.0/24 - R3


In this example R2 would anounce 10.0.0.0/8 to R3, because the update "leaves" the 10.0.0.0/8 network and "enters" into 192.168.1.0/24.

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


thanks

pkhatri Mon, 04/10/2006 - 04:36
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Yes... the boundary referred to here is the old classful boundary. So if you go from a 172.16.5.0/24 network to a 172.16.200.0/24 network, that will not be considered a network boundary since both of those networks are part of the class B network of 172.16.0.0/16. 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.


Paresh

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


yes a boundary would be between one classful network and another like 10/8 to 172.16/16 or 192.168.1.0/24 to 123.123/16 and so on.


Hope this helps! Please rate all posts.


Regards, Martin

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


thanks

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