Hi,
in order to mitigate layer 2 loops on my C6500, I'd like to implement ARP rate limiter.
Doing a span of arp traffic on the Sup720 rp & sp, I notice an average arp traffic of 10kb/s. I don't notice traffic peak, event with a 100ms step.
So I configured my rate limiter as following:
mls qos protocol arp police 64000 1000.
64000bps is far from the 10000bps I observed with span
1000 byte of Bc means, if I am correct, means burst of 1000bytes on a 125ms interval.
Looking at span result, my burst value shloud be enough to avoid policed packets. But is is not the case:
#sh mls qos protoc
Modes: P - police, M - marking, * - passthrough
Module: All - all EARL slots; Dir: I&O - In & Out; F - Fail
Proto Mode Sid Mod Dir AgId Prec Cir Burst AgForward-By AgPoliced-By
------------------------------------------------------------------------------------
ARP P 1 1 In 4 - 64000 1000 42908 3008
ARP P 1 2 In 4 - 64000 1000 19652 0
ARP P 1 5 In 4 - 64000 1000 16764 0
ARP P 1 6 In 4 - 64000 1000 61872 20928
ARP P 1 8 In 4 - 64000 1000 0 0
ARP P 2 1 In 4 - 64000 1000 20996 836
ARP P 2 4 In 4 - 64000 1000 3488 0
ARP P 2 5 In 4 - 64000 1000 12834 256
ARP P 2 6 In 4 - 64000 1000 42738 10304
ARP P 2 7 In 4 - 64000 1000 17430 640
ARP P 2 8 In 4 - 64000 1000 0 0
ARP P 2 9 In 4 - 64000 1000 5632 0
So I change Bc value for 4000 (Tc=500ms). There is still policed packets, but result is better (in the following outpur, all policed packet appeard in one time, so I guess during a burst):
Proto Mode Sid Mod Dir AgId Prec Cir Burst AgForward-By AgPoliced-By
------------------------------------------------------------------------------------
ARP P 1 1 In 4 - 64000 4000 53100 1088
ARP P 1 2 In 4 - 64000 4000 19912 0
ARP P 1 5 In 4 - 64000 4000 20446 0
ARP P 1 6 In 4 - 64000 4000 70236 20096
ARP P 1 8 In 4 - 64000 4000 0 0
ARP P 2 1 In 4 - 64000 4000 25728 0
ARP P 2 4 In 4 - 64000 4000 3344 0
ARP P 2 5 In 4 - 64000 4000 15468 0
ARP P 2 6 In 4 - 64000 4000 53796 6210
ARP P 2 7 In 4 - 64000 4000 23222 0
ARP P 2 8 In 4 - 64000 4000 0 0
ARP P 2 9 In 4 - 64000 4000 4928 0
Then I tried Bc = 8000 (Tc = 1s!). Quite no more policed packets.
[Edit] And finally, Bc = 16000 (Tc = 2s, which has no sense!!) => still packets policed (span indicate no peaks!):
Proto Mode Sid Mod Dir AgId Prec Cir Burst AgForward-By AgPoliced-By
------------------------------------------------------------------------------------
ARP P 1 1 In 4 - 64000 16000 1355426 12032
ARP P 1 2 In 4 - 64000 16000 553734 0
ARP P 1 5 In 4 - 64000 16000 480478 0
ARP P 1 6 In 4 - 64000 16000 2071666 33472
ARP P 1 8 In 4 - 64000 16000 0 0
ARP P 2 1 In 4 - 64000 16000 657224 3976
ARP P 2 4 In 4 - 64000 16000 94732 0
ARP P 2 5 In 4 - 64000 16000 404400 0
ARP P 2 6 In 4 - 64000 16000 1412826 35584
ARP P 2 7 In 4 - 64000 16000 518716 0
ARP P 2 8 In 4 - 64000 16000 0 0
ARP P 2 9 In 4 - 64000 16000 149308 0
I guess there is a misunderstanding of me with this burst value, or with the span interpretation.
Has someone any idea ?
Thanks!
