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Unanswered Question
mohammedmahmoud Sun, 04/29/2007 - 09:43
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Hi,


network 192.168.200.18 0.0.0.3 --> Matches 192.168.200.16/30


network 192.168.200.18 0.0.0.0 --> Matches 192.168.200.18/32


Accordingly the first one matches (192.168.200.16/30 - which is normal for point-to-point links) while the second will only match 192.168.200.18/32. EIGRP sends updates to the interfaces in the specified network(s). Also, if an interface's network is not specified, it will not be advertised in any EIGRP update.


Here you are the output when the router is configured with both (for example):


Routing Protocol is "eigrp 1"

Outgoing update filter list for all interfaces is not set

Incoming update filter list for all interfaces is not set

Default networks flagged in outgoing updates

Default networks accepted from incoming updates

EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0

EIGRP maximum hopcount 100

EIGRP maximum metric variance 1

Redistributing: eigrp 1

Automatic network summarization is in effect

Maximum path: 4

Routing for Networks:

192.168.200.18/32

192.168.200.16/30

Routing Information Sources:

Gateway Distance Last Update

Distance: internal 90 external 170




HTH, please rate if it does help,

Mohammed Mahmoud.



mohammedmahmoud Sun, 04/29/2007 - 12:31
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Hi,


Both /32 or /30 will work with no difference in your case, the network statement is only used to see which interface ip address matches it in order to be used to send and receive EIGRP updates, and in the same time its IP network is advertised (with the mask configured on the interface not the mask in the network command).


Lets take your case as an example:


R1 (192.168.100.17/30) <--> R2 (192.168.100.18/30)


Case1 using /32:

on R1 network 192.168.100.17 0.0.0.0

on R2 network 192.168.100.18 0.0.0.0


EIGRP adjacency will be up and they are going to exchange routes, but note that when they exchange this network with another router running EIGRP they'll send 192.168.100.16/30 not the /32s.


Case2 using /30:

on R1 network 192.168.100.16 0.0.0.3

on R2 network 192.168.100.16 0.0.0.3


EIGRP adjacency will be up and they are going to exchange routes, and also when they exchange this network with another router running EIGRP they'll send 192.168.100.16/30 (subnetmask configured on the interface).


Then what is the difference between both --> The trick here is that sometimes we use a single network command to match a range of interfaces by manipulating the subnetmask to include more than one interface ip, but it is not the case here.


Example:


Router with 2 interfaces: 192.168.100.1/30 and 192.168.100.5/30, if we use ""network 192.168.100.0/29" this will make the router sends/receives on both interfaces using 1 network statement.



I hope that i was informative, please don't hesitate for further questions.


HTH, please rate if it does help,

Mohammed Mahmoud.

guruprasadr Sun, 04/29/2007 - 23:42
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Hi Alsayed, [Pls Rate If Helps]


network 192.168.200.18 0.0.0.3


Will advertise below IP's in this Network:

192.168.200.16

192.168.200.17

192.168.200.18

192.168.200.19


Whereas:network 192.168.200.18 0.0.0.0 [Match All Octets in this IP]


Will advertise only 192.168.200.18 ONLY.


Both of this are Correct & Powerful too. Usage depends on your Requirement.


Pls Rate if Helps ! !


Best Regards,

Guru Prasad R

mohammedmahmoud Mon, 04/30/2007 - 00:32
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Hi there,


Unfortunately i do disagree with you, the network command will control which interface shall be used to send/receive EIGRP updates, but the updates are sent with the subnet mask of the interface itself not the wildcard mask of the network command.


HTH,

Mohammed Mahmoud.


Richard Burts Mon, 04/30/2007 - 05:37
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Guruprasad is not correct and Mohammed is correct about this. The network statement (and the optional mask) are used to determine which interfaces match the network statement and will be included in EIGRP. After deciding which interfaces to include the network statement is not used for anything else. Deciding what to advertise is based on the subnet mask of the interface.


HTH


Rick

mohammedmahmoud Mon, 04/30/2007 - 10:38
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Hi Rick,


Its nice having you as a reference here :)


BR,

Mohammed Mahmoud.

jbrunner007 Tue, 05/01/2007 - 05:33
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Great conversation guys!

Mohammed, you are very sharp!


Will you be joining me in taking the R&S lab this year?


-Joe Brunner

Richard Burts Tue, 05/01/2007 - 20:03
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Mohammed


Best of luck with the lab. Passing the written is a significant step, but the lab is an entirely different challenge. It takes focus and concentration, and flexibility. It was a great relief when I completed the lab. I look forward to congratulating you when you pass your lab.


HTH


Rick

mohammedmahmoud Tue, 05/01/2007 - 23:10
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Hi Rick,


Thank you very very much, i do agree with you that the written and the lab are entirely different, i can feel it while preparing, i am really looking forward to achieve it, please wish me luck.


P.S I am really benefiting a lot by interacting with experts like your self, and i am really looking forward to join the league :)


BR,

Mohammed Mahmoud.

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