setting up eigrp

Unanswered Question
Oct 31st, 2007
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Hi all


when setting up eigrp, say between 2 routers, if the interfaces between the 2 are 10.1.1.1/24 and the other interfaces are on say 192.168.1.0/24 and the other 192.168.2.0/24, could i put on both routers the statement , network 10.0.0.0 , or would i put network 10.1.1.0/24 ?


please help

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guruprasadr Wed, 10/31/2007 - 04:43
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HI Carl,


network 10.1.1.0

==>means longest match for the Subnet.


network 10.0.0.0

==>advertise the entire 10" Class A network.


Above is the difference.


DO RATE if HELPS


Best Regards,


Guru Prasad R

carl_townshend Wed, 10/31/2007 - 05:00
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if i advertised the 10.0.0.0 network, i gather it would include the interfaces in the 10.1.1.1/24 statement as they fall within that network? is it best to always use the longest match for adding networks, ie the mask of the interface

Kevin Dorrell Wed, 10/31/2007 - 05:06
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Guru, the bit about network 10.0.0.0 covering anything in the Class A 10.0.0.0 network is correct. But the bit about 10.1.1.0 needs some clarification.


If you supply network 10.1.1.0 then you will have to supply a wildcard match. For eample, if you supply network 10.1.0.0 0.0.255.255, then it will match any interface that has a base address between 10.1.0.0 and 10.1.255.255, regardless of its mask. So that command, for example, would cover interfaces that had addresses 10.1.0.0/24 and 10.1.26.128/25, all on one command.


The criterion is whether the base address of the interface falls within the wildcard mask of the network statement.


Kevin Dorrell

Luxembourg


guruprasadr Wed, 10/31/2007 - 05:14
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HI Kevin,


Thanks for adding more INFO with Eg.


HI Carl,


I accept with Kevin.


Advertising network 10.0.0.0 covering entire class A Network ==> No problem


network 10.1.1.0 has to be advertised with wildcard mask rather with Subnet mask.


Refer eg: provided by Kevin.


DO RATE all Helpful POSTS.


Best Regards,


Guru Prasad R

carl_townshend Wed, 10/31/2007 - 06:01
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i believe you do not need to use the woldcard mask anymore, it will take the normal way of inputting a mask.

merritt81 Wed, 10/31/2007 - 07:00
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To clarify the above comments a bit consider this. By defining a network in the EIGRP configuration you are not advertising that particular network so to speak. Rather, you are enabling the transmission of EIGRP multicast or unicast packets out that particular interface that contain the network the interface belongs to.


For example, if you have a router with two interfaces, 10.1.1.1/24 and 10.2.2.1/24 and you use the following configuration


router eigrp 100

network 10.1.1.1 0.0.0.0

no auto-summary


You have only enabled EIGRP on that specific interface and will only advertise that particular network to adjacent neighbors.


If you configure the following:


router eigrp 100

network 10.0.0.0

no auto-summary


You will advertise both networks, 10.1.1.0/24 and 10.2.2.0/24 out both interfaces. You will NOT advertise the 10.0.0.0/8 network. Furthermore, you can not advertise a network that is not directly connected to the router.


If you are interested in advertising a network but not sending EIGRP packets out that interface consider using the passive-interface or redistribute connected features.

carl_townshend Thu, 11/01/2007 - 08:57
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Hi


so bascially if i added the 10.0.0.0/8 statement, these interfaces fall within that subnet, but it will look at what mask the actualt interfaces are in and advertise that network ?

guruprasadr Thu, 11/01/2007 - 21:48
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HI Carl, [Pls Rate if HELPS]


You have advertised "/8" Mask Bits.


Subnet Mask: 255.0.0.0

Host Address Range: 10.0.0.1 - to - 10.255.255.254

Subnet ID: 10.0.0.0

Broadcast ID: 10.255.255.255


PLS RATE if HELPS


Best Regards,


Guru Prasad R



carl_townshend Fri, 11/02/2007 - 03:16
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Hi Guru, in the comment posted previous, it says


"You will NOT advertise the 10.0.0.0/8 network. Furthermore, you can not advertise a network that is not directly connected to the router. "


so i presume that means if i have 2 interfaces on 10.1.1.1/24 and 10.2.2.2/24 the router will not advertise the 10.0.0.0/8 as its not directly connected


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