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Official Lammle User Forum

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  1. #1
    Join Date
    Nov 2009
    Posts
    3

    Question Subnet masks in OSPF

    Greetings.

    On page 476, you give the following command

    (config-router)#area 1 range 192.168.10.64 255.255.255.224

    Now, I had thought that you ALWAYS used Wildcard Masks with OSPF, and not Subnet Masks. No mention is made of the mask one way or another in the text.

    My question is, is this a unique exception to the "WildCard Masks in OSPF Rule"? Am I oversimplifying the situation? Is there anywhere else in OSPF where you use Subnet Masks?

    Please clarify.

    Thanks.

  2. #2
    Join Date
    Mar 2008
    Posts
    2,887

    Default

    The key word here is range.

    Quote Originally Posted by listmeister View Post
    (config-router)#area 1 range 192.168.10.64 255.255.255.224
    The area range command is used only with Area Border Routers (ABRs). It is used to summarize routes for an area.
    The result is that a single summary route is advertised to other areas by the ABR. Routing information is summarized at area boundaries.
    External to the area, a single route is advertised for each address range.(route summarization)
    Multiple area router configuration commands specifying the range option can be configured. Thus, OSPF can summarize addresses for many different sets of address ranges.

    HTH.
    Maddox Thomas-Clark 14/10/2008
    Bean Thomas-Clark 18/09/2007
    Big Evils Cisco World
    Linkedin

  3. #3
    Join Date
    Nov 2009
    Posts
    3

    Default

    I understand what the command does, but I'm still not clear why you use subnet masks with the range keyword and wildcard masks everywhere else in OSPF. Given that subnets are defined with wildcard masks, I would expect that a range of subnets would be too (but I would be wrong, I guess).

    Is this the only subnet mask (as opposed to wildcard mask) in the OSPF world?

    Thanks for your help.

  4. #4
    Join Date
    Mar 2008
    Posts
    2,887

    Default

    I think so.
    I don't know of another syntax in ospf that uses subnet mask.
    Maddox Thomas-Clark 14/10/2008
    Bean Thomas-Clark 18/09/2007
    Big Evils Cisco World
    Linkedin

  5. #5
    Join Date
    Dec 2006
    Posts
    2,221

    Default Just for fun.....

    why did OSPF use wildcards to begin with? What was the point? The same thing can be accomplished using a subnet mask.
    Well since it was created during the time of LSD, that's my best guess...

    Anytime you are summarizing, either between areas with OSPF, or using the ip summary-address command, you use regular subnet masks.

    For all other OSPF commands, you use the LSD way of doing things...

    Cheers!
    Todd Lammle

  6. #6
    Join Date
    Nov 2009
    Posts
    3

    Default

    Thanks. That clears it up.

  7. #7
    Join Date
    Mar 2008
    Posts
    2,887

    Default

    Lol @ tl..!
    Maddox Thomas-Clark 14/10/2008
    Bean Thomas-Clark 18/09/2007
    Big Evils Cisco World
    Linkedin

  8. #8
    Join Date
    Jan 2010
    Posts
    1

    Default Computer Problems need help PLEASE!?

    Hi, just wondering if anyone can help with a problem I'm having? I'm connected to the internet and it will let me open google but if I try to open another webpage it tells me the page cannot open. I already checked the firewall and everything seems fine, i also scanned for viruses with Avira and Mallware Byte and nothing showed up. If anyone can help it'd be much appreciated thanks! unlock iphone 3g

  9. #9
    Join Date
    Jan 2010
    Location
    Gaithersburg, MD
    Posts
    12

    Default

    You can just copy and paste the error message when you r trying to visit another URL, and then google it. It would explain via forums how to solve it.

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