02-04-2009 06:46 PM - edited 03-04-2019 01:06 AM
Hi,
I got the config of CE router of one my provider and I want to undestand QoS is doing and the statement on g0/1 "max-reserved-bandwith 85" makes any difference or not.
Here is the config:
!
class-map match-all BH
description Bursty-High
match any
class-map match-any ROUTING
match ip dscp cs6
match ip dscp cs7
match access-group 199
!
!
policy-map CE-PE-CHILD
description CE Egress Policy Map faced to PE
class ROUTING
police cir 16000 bc 8000 be 8000
conform-action set-dscp-transmit cs6
exceed-action set-dscp-transmit cs6
class BH
bandwidth 2652
random-detect dscp-based
police cir 2700000 bc 27000 be 27000
conform-action set-dscp-transmit af31
exceed-action set-dscp-transmit af32
class class-default
fair-queue
policy-map CE-PE-PARENT
class class-default
shape average 2700000 27000 0
service-policy CE-PE-CHILD
!
!
!
interface GigabitEthernet0/1
description << MPLS WAN >>
bandwidth 3000
ip address <Removed>
no ip redirects
no ip unreachables
no ip proxy-arp
load-interval 30
duplex full
speed 100
media-type rj45
no cdp enable
max-reserved-bandwidth 85
service-policy output CE-PE-PARENT
!
access-list 197 remark BL
access-list 197 permit ip any any dscp cs2
access-list 197 permit ip any any dscp 17
access-list 197 permit ip any any dscp af21
access-list 197 permit ip any any dscp 19
access-list 197 permit ip any any dscp af22
access-list 197 permit ip any any dscp 21
access-list 197 permit ip any any dscp af23
access-list 197 permit ip any any dscp 23
access-list 198 remark BH
access-list 198 permit ip any any dscp cs3
access-list 198 permit ip any any dscp 25
access-list 198 permit ip any any dscp af31
access-list 198 permit ip any any dscp 27
access-list 198 permit ip any any dscp af32
access-list 198 permit ip any any dscp 29
access-list 198 permit ip any any dscp af33
access-list 198 permit ip any any dscp 31
access-list 198 permit ip any any dscp cs6
access-list 198 permit ip any any dscp cs7
access-list 199 permit tcp any eq bgp any
access-list 199 permit tcp any any eq bgp
access-list 199 permit ospf any any
02-04-2009 07:51 PM
Hi Tayeb,
max-reserved bandwidth is used to specify how much interface bandwidth can be assigned to CBWFQ classes. By default this is 75%.
So in your case CBWFQ classes get 85% of 3000Kbps.
HTH
Lejoe
02-05-2009 05:17 AM
As Lejoe notes, max-reserved-bandwith allows you to determine how much bandwidth CBWFQ can explictly define. However, I'm unsure how this rules interacts with a hiearchal policy, such as your example.
The parent policy doesn't define bandwidth in class-default, although its shaper defines 2.7 Mbps which is 90% of the link's 3 Mbps. Only the child policy BH class defines 2,652 Kbps, which is 98.2% of the parent shaper's 2.7 Mbps (or 88.4% of the link's 3 Mbps).
So, it appears that "max-reserved-bandwith 85" might be unnecessary for such a configuration since some of the explicit bandwidths appears to exceed it.
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