Performance on Cisco 3945 running IOS 15.3(3)

[david.tran]

I have a very simple scenario with Cisco 3945 running IOS c3900-universalk9-mz.SPA.153-3.M.bin with two interfaces g0/0 (external) and g0/1 (internal).

I setup NAT on the router as follows:

ip cef

interface g0/0

  ip address 1.1.1.1 255.255.255.252

  ip nat outside

interface g0/1

  ip address 192.168.1.254 255.255.255.0

  ip nat inside

ip access-list extended nat

  permit ip 192.168.190.0 0.0.0.255 any

ip nat inside source list nat interface g0/0 overload

then I have a linux host with ip address 192.168.1.254 behind g0/1 with the gateway of the router 192.168.1.254.  I am able to push 950Mbps through the router without any issues.  So far so good.

No I decide to create an ACL and apply this ACL on interfage g0/0:

ip access-list extended External

  permit ip any any log

interface g0/0

  ip access-group External in

When I apply the ACL on the External interface, the throughput on the router goes from 950Mbps down to 160Mbps, an 80% drop in performance.  Why?

Anyone knows how to improve this?

Thanks,

[Lei Tian]

Hi,

Is the log keyword. Log will force the packet being process switched, so performance will drop.

HTH,

Lei Tian

[david.tran]

Thanks.  That does work.  However, that does not explain the fact that I am not seeing performance issues on the ASR 1002 and I have about 2000 lines of ACL on the ASR external interface.

[Joseph W. Doherty]

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Posting

The ASR is a different architecture, it has hardware forwarding.  (Note: the ASR 1K series, seems to be somewhat like the earlier 7300 series with NSE-100 or -150 or the 7200 series with NSE-1.)

Additionally, the prior 7200s, but not ISRs, had a "compiled ACL" feature that would improve performance for lengthy ACLs - don't know if the ASR 1K has that too.

Non-technically, 3945 vs. ASR 1002 is comparing apples to oranges. 

[Lei Tian]

Hi,

ASR is different platform. It uses hardware offload most if the features, just like 6500, 7600. If still not convinced, hope the following document help.
http://www.cisco.com/web/about/security/intelligence/acl-logging.html

HTH,
Lei Tian

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