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Forum Replies

  1. system says:

    Awesome way of explaining!! Thanks..I never EVER Leave a comment anywhere,but could not help here :slight_smile:

  2. Hi @wisamani,

    If you don't supply a wildcard then EIGRP will assume you want the whole network to be advertised. Here's an example:

    Router(config)#router eigrp 1
    Router(config-router)#no auto-summary 
    Router(config-router)#network 1.1.1.0

    This is what is stored in the running config:

    Router#show run | begin router eigrp
    router eigrp 1
     network 1.0.0.0

    1.1.1.0 falls under the class A 1.0.0.0/8 range so that's what EIGRP adds to the running config. If you don't want this, you have to add a wildcard:

    Router(config)#router eigrp 1
    Router(config-router)#no network 1.0.0.0
    Router(config-router)#network 1.1.1.0 0.0.0.255

    And you will get:

    Router#show run | begin router eigrp
    router eigrp 1
     network 1.1.1.0 0.0.0.255

    Even without the wildcard, it would have worked but enabling EIGRP for all 1.x.x.x networks might not be what you want.

    I didn't have to do this for 192.168.12.0 since that's a class C network. If I used a /25 - /30 subnet mask then I would have to add the correct subnet mask.

    Hope this helps!

  3. Hello Rene,

    Your site is great and easy to understand.

    In this topic i understand the part which you had mention if you don't specify the wild card which command is stated below :

    !
    no auto- summary
    router eigrp 1 network 1.1.1.0  **0.0.0.255**
    !

    then in result, you’ll find “network 1.0.0.0/8” in your show run.

    However when i read about the topic on RIP - "How to configure RIP on cisco router"

    In the statement
    "You can see that R2 has learned about network 172.16.1.0 /24 and 172.16.2.0 /24. This is because R1 and R3 are advertising 172.16.1.0 /24 and 172.16.2.0 /24, not 172.16.0.0 anymore. R1 and R3 also have learned about each other’s networks."

    I am abit confused because i realize there is no wildcard added for the network command.

    Is there a difference in concept for RIP and EIGRP regarding the network and wildcard command ?

    I mean in another word, no auto-summary for RIP, why i see there is no wildcard 0.0.0.255 for 172.16.1.0/24 and 172.16.2.0/24 network ?

    Thank you

    Chan

  4. Hello Qifeng

    In EIGRP, if you don't use the no auto-summary command, the router will assume a classful network address regardless of the wildcard mask you enter.

    Once you enter the no auto-summary command, EIGRP will begin sending the wildcard mask information as well.

    As for RIP, version 1 will send classful routing information. In order to send classless routing information, RIP must be configured to use Version 2 AND must include the no auto-summary command.

    Now the difference between EIGRP and RIP is that when you configure the network command for RIP, you don't input a wildcard mask. It won't let you. Take a look at this output:

    Router#
    Router#configure terminal
    Enter configuration commands, one per line.  End with CNTL/Z.
    Router(config)#router rip
    Router(config-router)#version 2
    Router(config-router)#network 172.16.0.0 ?
      <cr>
    Router(config-router)#network 172.16.0.0 
    Router(config-router)#

    The only option it gives you after the network address is <cr>.

    So in RIP, if you configure version 2 and no auto-summary, the router will use the subnet mask configured on the interface associated with the network. So for the example you used, if you have two interfaces with IP addresses 172.16.1.1/24 and 172.16.2.1/24 respectively and you configure those networks using RIP, it will use the subnet masks (/24) configured on the interfaces themselves.

    I hope this has been helpful!

    Laz

  5. That's really helpful, thanks Laz!

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