From: Pierre-Alex (paguanel@hotmail.com)
Date: Mon Jun 05 2006 - 06:37:46 ART
Hi Group,
I just clarified some big misunderstanding regarding the default-class through
a small lab.
When the Cisco doc says that 25% is reserved for L2 control traffic by
default, this is actually NOT allocated to the class-default
but to the system high-priority flag queue (Cisco reference on different type
of system queues at the end of this e-mail).
I verified this by doing the following:
I sent three continuous ping on R1 destined to R4 loopbacks l0, l1 and l2 .
l0 and l1 traffic are classified. l2 traffic is not.
In one case (Case 1) I allocate nothing to the class-default and the other
(Case 2) I allocate 1% of network traffic.
I check to see whether r4 receives any traffic for l2 inbound
Diagram
R1 -traffic to loopbacks >>>>------R3----ser 0/0 (128Kbps) -----------R4 -
Looback r4-l0 , r4-l1 , r4-l2
Case 1:
No bandwidth allocation to default-class on R3 ser 0/0:
policy-map CBWFQ_percentage6
class bgp-traffic
priority 8
class to-r4-l0
bandwidth remaining percent 10
class to-r4-l1
bandwidth remaining percent 90
class class-default
Verification on R4:
You can see that traffic rate class-default is 0
r4#sh policy-map interface
Serial0/0
Service-policy input: CBWFQ_percentage2
Class-map: to-r4-l0 (match-all)
0 packets, 0 bytes
30 second offered rate 0 bps
Match: access-group 104
Class-map: to-r4-l1 (match-all)
21759 packets, 32725536 bytes
30 second offered rate 127000 bps
Match: access-group 144
Class-map: to-r4-ser0 (match-all)
0 packets, 0 bytes
30 second offered rate 0 bps
Match: access-group 154
Class-map: class-default (match-any)
5148 packets, 347995 bytes
30 second offered rate 0 bps, drop rate 0 bps ----> HERE
Match: any
Case 2:
On r3 allocation of 1percent of remaining traffic to default-class.
policy-map CBWFQ_percentage7
class bgp-traffic
priority 8
class to-r4-l0
bandwidth remaining percent 10
class to-r4-l1
bandwidth remaining percent 89
class class-default
bandwidth remaining percent 1
Verification on R4:
you can see that traffic for r4-l2 (non classified) has 2000 bps
r4#sh policy-map interface
Serial0/0
Service-policy input: CBWFQ_percentage2
Class-map: to-r4-l0 (match-all)
0 packets, 0 bytes
30 second offered rate 0 bps
Match: access-group 104
Class-map: to-r4-l1 (match-all)
24086 packets, 36225344 bytes
30 second offered rate 125000 bps
Match: access-group 144
Class-map: class-default (match-any)
5650 packets, 407676 bytes
30 second offered rate 2000 bps, drop rate 0 bps ----> HERE
For reference:
http://www.cisco.com/en/US/tech/tk543/tk544/technologies_tech_note09186a00800
94612.shtml
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