[Dshield] ACL impact on router performance

Lauro, John jlauro at umflint.edu
Thu Feb 19 22:00:13 GMT 2004

It really depends on the router.  Some routers handle the acls all in
hardware and some all in software, some a combination (ie, first
packet in software the rest in hardware), etc...  Without being given
a specific model number for the router, it could be a 15% hit, or it
could be no impact, etc...

> -----Original Message-----
> From: list-bounces at dshield.org 
> [mailto:list-bounces at dshield.org] On Behalf Of Jon R. Kibler
> Sent: Thursday, February 19, 2004 2:25 PM
> To: list at dshield.org
> Subject: [Dshield] ACL impact on router performance
> Hello all:
> Does anyone have any hard stats on the impact of ACLs on 
> router performance?
> I have heard many people (usually those who vigorously oppose 
> router-based filtering) claim that just enabling ACLs causes 
> a 15% performance hit, and that each ACL causes about a 0.5% 
> additional degradation. This seems to be the standard mantra 
> among those that dislike ACLs, or any other network-based filtering.
> We run several Cisco routers with about 200 ACLs on each 
> inbound interface and about 30 ACLs on each outbound 
> interface and do not see any noticeable performance 
> degradation. However, our networks are FAR from saturated.
> A recent discussion on insecure.org seemed to say that if you 
> had enough RAM in your router, the impact of ACLs seems to be 
> minimal. Google doesn't seem to find any vendor published 
> documents that provide stats. (Except one optical router that 
> claimed it was independently tested with 10K ACLs and still 
> able to run at maximum line speed.)
> Does anyone have any good information on this subject?
> TIA!
> Jon
> -- 
> Jon R. Kibler
> Chief Technical Officer
> A.S.E.T., Inc.
> Charleston, SC  USA
> (843) 849-8214
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