CCIE Pursuit Blog

July 1, 2007

IP Prefix List Operators In A Nutshell

Filed under: IOS,Tech Tips — cciepursuit @ 11:53 am

I am not well aquainted with the IP prefix command.  It’s pretty straight-forward and I understand the basics, but the operators (ge(greater than) and le(less than)) always throw me off.  Not any longer, thanks to this post:

It’s all about the number of bits! 

If you want /20 to /32, that would be a number greater than or equal to 20 (ge 20)

If you want /0 to /20, that would be a number less than or equal to 20 (le 20)

If you want /20 to /24, that would be a number greater than or equal to 20 AND less than or equal to 24 (ge 20 le 24)

If you want ONLY /24’s, that would be a number both greater than or equal to 24 AND less than or equal to 24, which essentially cancels out the greater than/less than part and leaves you equal to 24 (ge 24 le 24).

HTH,
Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, JNCIE
#153, CISSP, et al.
CCSI/JNCI-M/JNCI-J
VP – Technical Training – IPexpert, Inc.
IPexpert Sr. Technical Instructor

It makes sense now.  

Here are a couple of other GroupStudy links that have good information about IP prefix lists:

http://www.groupstudy.com/archives/ccielab/200404/msg00539.html

http://www.groupstudy.com/archives/ccielab/200310/msg01417.html

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