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network boundary

carl_townshend
Spotlight
Spotlight

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

summarization would only occur when routes cross a network boundary

5 Replies 5

mheusinger
Level 10
Level 10

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

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

thanks

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

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

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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