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In area 0 I have two loopbacks: 172.16.2.2 and 172.16.2.3 (both /24's).

I'm trying to configure a summary to roll the two up. Given the rest of the topology, I'm using area X range command.

This is my input and the console's output. What am I missing?

ZEUS(config-router)#area 0 range 172.16.2.0 255.255.252.0
% OSPF: Inconsistent address/mask 172.16.2.0/22 for area range

Wouldn't this summarize from 172.16.2.2 up to 172.16.3.255?

  • It might be useful to post relevant bits of the configurations as well as the platform/software version(s). – John Jensen Dec 12 '13 at 20:34
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All loopbacks in OSPF are advertised with a 255.255.255.255 mask by default (see "LOOPBACK" network type), regardless of what you've configured the netmask as on the interface. If you want to announce your loopbacks with anything that's not a /32 you need to configure them as point-to-point (ip ospf network point-to-point under the Loopback interface configuration).

EDIT: Since you've stated you've already done this, my next observation is that you've given the wrong network address for the area range command. If you want to announce the summary you'd need to announce it with the network address, ie area 0 range 172.16.0.0 255.255.252.0

Also be aware that any traffic to 172.16.0.0/24 or 172.16.1.0/24 will be blackholed.

EDIT #2: @Christian's answer is also correct if you wanted to summarize just those two /24's into a /23: area 0 range 172.16.2.0 255.255.254.0

  • I've already done that, lets stay on topic, I'm asking why do I get the inconsistent address/mask feedback, when I know for a fact that the range of 172.16.2.0 255.255.252.0 includes both loopbacks? – A L Dec 12 '13 at 20:39
  • 1
    See my updated answer. – John Jensen Dec 12 '13 at 20:49
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    I figured it out: wrong subnetting! Gragh, need to practice more. It's inconsistent because .2 is half way through a block of 4 /24's, I moved it up to 172.16.4.0 255.255.252.0 to test this and it worked. Doing 172.16.2.0 255.255.254.0 also worked to summarize the two loopbacks I had. Thanks for all of your help, and enduring my ignorance! – A L Dec 12 '13 at 21:26
  • A,L you wanted 2.0 thru 3.255. If you still want this range specifically simply change it to /23. See my answer – Michael May Dec 12 '13 at 22:21
  • He already noted that in his comment above yours... – John Jensen Dec 12 '13 at 22:24
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172.16.2.0 255.255.252.0 = 172.16.0.0-172.16.3.255

If you want .2.0 thru .3.255 specifically you'll need

172.16.2.0 255.255.254.0 = 172.16.2.0-172.16.3.255

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