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QOS to limit outbound traffic to DSL

Setup:

Cisco Catalyst 2970G 28Port Gigabit Switch WS-C2970G-24TS-E

GigabitEthernet0/1 connected to DSL equipement connecting to the Internet

GigabitEthernet0/9 connected to the network that is to limit its equipments outbound Internet speed.

This is what I have configured so far:

access-list 101 deny   ip 192.168.1.0 0.0.0.255 192.168.1.0 0.0.0.255

access-list 101 permit ip any any

mls qos srr-queue output dscp-map queue 2 threshold 1  38

this puts anything marked with DSCP decimal 38 into queue 2

policy-map intg09

  class intg09

   set ip dscp af43

this assigned to g0/9 sets traffic as per the ACL to be DSCP af43 (decimal 38)

interface GigabitEthernet0/9

service-policy input intg09

!

this shows the policy applied to the interface

interface GigabitEthernet0/1

srr-queue bandwidth share 10 1 1 1

priority-queue out

This gives queue 1 priority over everything and ten times more packets serviced than queues 2/3/4

Queue 1 would be everything other than traffic from Gi0/9

Queries:

Overall it does not appear to be working, as traffic from say Gi0/9 and Gi0/10 equally share the outbound bandwidth to the internet

It appears that any traffic from equipment on GigabitEthernet0/9 even if it is not destined for the Internet (GigabitEthernet0/1) is limiting its LAN speeds.

Something that might be related to the above, is that I am monitoring the Traffic on (GigabitEthernet0/1) via:

monitor session 1 source interface Gi0/1

monitor session 1 destination interface Gi0/3


but am seeing a lot of non Internet related traffic on Gi0/1, via its SPAN on Port 3.

ie/ Traffic from a Host on Gi0/15 to a Host on Gi0/16 or Hosts on Gi0/09(with the above QOS) to a Host on Gi0/16

Any ideas of my issues?

Regards,

Alby


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1 REPLY
Super Bronze

Re: QOS to limit outbound traffic to DSL

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Posting

interface GigabitEthernet0/1  

srr-queue bandwidth share 10 1 1 1

priority-queue out

This gives queue 1 priority over everything and ten times more packets serviced than queues 2/3/4

Queue 1 would be everything other than traffic from Gi0/9

You're correct that Q1, with PQ enabled has priority over all the other queues, but I believe Q1 doesn't get 10x the packets serviced, it should get any of its packets serviced first until there are no more.  I.e. PQ can starve bandwidth from all other queues.

You realize queuing priorities are difficult to "measure" except when the interface is congested, i.e. while packets are queued in multiple queues all the time.  Is this the case?

It appears that any traffic from equipment on GigabitEthernet0/9 even if it is not destined for the Internet (GigabitEthernet0/1) is limiting its LAN speeds.

Once QoS is enabled, and you've mapped g0/9's bandwidth to a specific queue and threshold, it's possible QoS settings (default?) are limiting it's maximum transfer rate.  I'm not familiar with the 2970 series, but the 2960/3560/3750 series all often slow traffic, when there's congestion, because their buffer resources often lead to premature packet drops.  Are packet drops being registered on Q1 on other interfaces?

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