06-06-2007 07:06 AM - edited 03-05-2019 04:31 PM
Hi, I'm having trouble understanding the documenation on prefix lists -
examples like this don't make sense to me since you'll never see a network addr like 172.20.10.171/16... why wouldn't this be 172.20.0.0/16 since 172.20.0.0 is the only network addr with the /16 mask?
ipv4 prefix-list list1
10 permit 172.20.10.171/16 le 24
If anyone can point me to a good book or article or white-paper on this I'd really appreciate it.
Thanks, Lisa G
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06-06-2007 07:42 AM
Lisa,
This doesn't make sense indeed. If you enter something like 172.20.10.171/16, IOS automatically converts it to 172.20.0.0/16.
Can you please give me the URL, where this combination is used. I will bring it up with out documentation team.
Hope this helps,
06-06-2007 01:10 PM
Lisa,
You are absolutely correct. Any prefix in 10/8 with a prefix length between 24 and 32 inclusively would match that statement.
Hope this helps,
06-06-2007 07:42 AM
Lisa,
This doesn't make sense indeed. If you enter something like 172.20.10.171/16, IOS automatically converts it to 172.20.0.0/16.
Can you please give me the URL, where this combination is used. I will bring it up with out documentation team.
Hope this helps,
06-06-2007 09:29 AM
Hi,
Here's the url -
http://cisco.com/en/US/docs/ios_xr_sw/iosxr_r2.0/addr_serv/command/reference/3irpref.html
Thx!! Lisa
PS I haven't found any good documentation on prefix-lists (even though I'm pretty sure I understand it now). Do you know of any white papers or url's?
Enke Chen once wrote a little how-to sheet when he created prefix lists which was passed around Cisco but that never made it on the Cisco web site.
LisaG
06-06-2007 01:18 PM
Lisa,
Thanks for the URL. I will make sure our documentation folks fix it. I found the paper that Enke had produced back then and I'm attaching it.
Hope this helps,
06-06-2007 11:28 AM
Hi,
I have one more question about the prefix lists....
if you say permit 10.0.0.0/8 ge /24 le /32
that would permit
10.0.0.0/8 with masks from 255.255.255.0 through 255.255.255.255?
Someone in my group thinks that le /24 means /25 though /32 but I think this is the opposite.
Thanks!!
LisaG
06-06-2007 01:10 PM
Lisa,
You are absolutely correct. Any prefix in 10/8 with a prefix length between 24 and 32 inclusively would match that statement.
Hope this helps,
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