nanog mailing list archives

Re: Filtering Source Addresses on gw-internet


From: "C. Jon Larsen" <jlarsen () ajtech com>
Date: Wed, 13 Aug 1997 06:46:58 -0400 (EDT)

Much thanks to everyone for their input. Greg, since you have "Cisco" in your 
email address, any comment on whether sending packets to a null interface is a
quicker / more efficient way blocking unwanted traffic ? gw-internet is a
little old 68030, with 1MB RAM.

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At 03:05 PM 8/12/97 -0400, C. Jon Larsen wrote:
gw-internet#show access-lists 120
Extended IP access list 120
   deny   ip any 10.0.0.0 0.255.255.255 log
   deny   ip any 172.16.0.0 0.0.255.255 log
   deny   ip any 172.17.0.0 0.0.255.255 log
   deny   ip any 192.168.0.0 0.0.255.255 log
   permit ip a.b.c.0 0.0.0.255 any (27429 matches)
   deny   ip any any log

Line 2 and 3 could be replaced by
deny ip any 172.16.0.0 0.15.255.255 log

which would block all 172.16.0.0-172.31.0.0 as per the RFC.

You might also want to block 127.0.0.0.

GK

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Linux.

+-------------------+---------------------+
| C. Jon Larsen     | jlarsen () ajtech com  |
| Systems Engineer  | Tel: 804.353.2800   |
| A&J Technologies  |                     |
|-------------------+---------------------|
|         http://www.ajtech.com           |
+-----------------------------------------+



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