From: Tim Fletcher (groupstudy@fletchmail.net)
Date: Fri Aug 29 2003 - 20:47:30 GMT-3
Your're partially right. To block 172.16.0.0 to 172.31.255.255 you would use a /12. The /16 would only block 172.16.0.0 to 172.16.255.255, not the range you listed below.
-Tim Fletcher
At 12:18 PM 8/28/03 +0100, Bola Adegbonmire wrote:
>Hi all,
>I was wondering if someone can please help me out with a prefix-list for denying rfc 1918 addresses. I was doing a lab in which I am expected to filter out BGP updates containing these adress ranges received from backbone.
>
>I saw a solution like this
>
>ip prefix-list in seq 5 deny 10.0.0.0/8 le 32
>ip prefix-list in seq 5 deny 172.16.0.0/16 le 32
>ip prefix-list in seq 5 deny 192.168.0.0/16 le 32
>
>My dispute is with the 172.16.0.0 addresses (though I am not sure correct line). The reson is the only class B teaditional addresses are 172.16.0.0 - 172.31.0.0 meaning 172.32.0.0 is not an RFC 1918 addresses. My understanding is the prefix-list will block addresses 172.16.32.0/16 - 172.254.0.0/16 which are not RFC 1918 addressses.
>
>Thanks!
>
>Bola Adegbonmire
>Networks
>Resourcery Limited
>18 Adeola Hopewell, Victoria Island.Lagos-Nigeria.
>Tel:234-1-3200301, 4618281, 7740711-2 ( Ext:1644)
>
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