Qos policy-map

[Pawan Raut]

We have WAN interface having BW 100Mbps and wanted to configure QoS so that any server source 10.1.1.0/24 to destination 10.2.1.0/24 should have dedicated BW 20Mbps and rest should get allocated to all other traffic Will this archive with below configuration? What I haven't define class-default in policy-map will it drop the remaining traffic?

ip access-list extended Server-ACL
permit ip 10.1.1.0 0.0.0.255 10.2.1.0 0.0.0.255
!
class-map match-all Server-Class
match access-group name Server-ACL
!
policy-map Server-Qos
class Server-ACL
shape average 20000000
!
interface GigabitEthernet0/0/0

des WAN interface
service-policy output Server-Qos
bandwidth 100000
!

[paul driver]

Hello
The below is a very simple example of a Hqos that will provide a minimum bw of 20mb to the server class and provide fair queuing to the rest of the traffic, it doesn't show or allocate classification of any routing protocols and management traffic in times of congestion which is recommended.

Example Hqos:
policy-map child
class Server-ACL
bandwidth 20480 < minimum bw allocation
class class-default
fair queue

policy-map parent
class class-default
shape average <wan committed access rate in bps)
service-policy child

interface GigabitEthernet0/0/0
des WAN interface
service-policy output parent

[Joseph W. Doherty]

Actually, without a bandwidth allocation for class-default, unsure what the bandwidth 20 Mbps will do on different platforms and/or IOS versions.

[Georg Pauwen]

Hello,

even when you do not specifically define the default class, it is still created (by default). So all traffic that does not match any of the defined classes goes to the default class. The default queuing for the default class used to be WFQ, not sure if that is true in all cases, and for all IOS versions...

R1#show policy-map interface gigabitEthernet 0/0
GigabitEthernet0/0

Service-policy output: Server-Qos

Class-map: Server-Class (match-all)
0 packets, 0 bytes
5 minute offered rate 0000 bps, drop rate 0000 bps
Match: access-group name Server-ACL
Queueing
queue limit 64 packets
(queue depth/total drops/no-buffer drops) 0/0/0
(pkts output/bytes output) 0/0
shape (average) cir 20000000, bc 80000, be 80000
target shape rate 20000000

Class-map: class-default (match-any)
9 packets, 835 bytes
5 minute offered rate 0000 bps, drop rate 0000 bps
Match: any

queue limit 64 packets
(queue depth/total drops/no-buffer drops) 0/0/0
(pkts output/bytes output) 9/835
R1#

By the way, make sure to correct the syntax error in your config:

class-map match-all Server-Class
match access-group name Server-ACL
!
policy-map Server-Qos
class Server-ACL --> this need to be class Server-Class
shape average 20000000

[Joseph W. Doherty]

"The default queuing for the default class used to be WFQ, not sure if that is true in all cases, and for all IOS versions..."

In pre-HQF CBWFQ, FQ defined in class-default used WFQ (also not limited to just class-default BW allocation) but unless FQ configured, class-default used FIFO.

In post-HQF CBWFQ, FQ can be defined in all classes but LLQ classes) and it use FQ. Again, if not configured, classes use FIFO.

[Joseph W. Doherty]

No, your policy doesn't guarantee 20 Mbps, although it limits server traffic to 20 Mbps.

Is the 100 Mbps a logical or physical limit. I.e. is gig interface running at 100 Mbps or gig?

If physical (interface running at 100 Mbps):

policy-map Server-Qos
class Server-Class
bandwidth percent 20
class class-default
bandwidth percent 80

I would suggest using FQ in both classes.

If logical (interface running at gig):

policy-map Server-Qos
class class-default
shape average 100000000 !BTW I believe some devices don't account for L2 overhead, if so, set about 15% less
service-policy Server-Qos-child

policy-map Server-Qos-child
class Server-Class
bandwidth percent 20
class class-default
bandwidth percent 80

I would still suggest using FQ in both classes.

FQ works so well, there's a good change all you may need is class-default containing just it. I.e. no need to reserve bandwidth for your server's traffic.