QoS issue when connecting to server with a gigabitNIC on a diff subnet

[PHead2]

I'm having an issue when enabling QoS on a set of 3750 switches:

With QoS enabled traffic is very slow when a client with a 100BaseT connection pulls data off of a server with a gigabit connection and the server is on a different subnet(VLAN) than the client. The is no (noticeable) effect on speed if the client uploads a file to the same server(s). There is no problem if the client is on the same subnet as the server (regardless of the connection speeds) or if the client is on a different subnet but also has a gigabit connection to the switch stack.

I have tried every combination of different subnets (there are 5 VLANs), servers, NICs, etc. using quite a few different boxes as servers and clients. The problem only comes up when the 100BaseT box is downloading from a 1000BaseT box on a different subent...

I am totally stumped on this, anyone have any ideas?

 

[gnomi]

well.. some more data would be useful. what's the IOS version, what's the QoS config that makes trouble...? what do you mean by slow download?
just to start...

regards
M.

 

[PHead2]

The switches are running 12.1(19)EA1c, the SMI version. rip is used for routing between vlans.

What I mean by slow download is that as soon as QoS is enabled on the switch stack (mls qos) the transmission rate when a client is pulling data from a server (only in the stated cases (100BaseT client, 1000BaseT Server on different vlans) slows down tremendously. I can't really quantify it on the spot but it's almost as if the 100BaseT client only has a 10BaseT connection (only to gigabit servers of course, it is fine with nongigabit servers or any server on the same vlan).

The current QoS config is auto-qos for cisco phones. I should note that it does this even if there is no qos conifg other than qos being enabled.

 

[ADB100]

Simply 'mls qos' is nowhere near enough to get qos working correctly. The 3750 (and 3560 and 2970) are quite complex when it comes to qos and a design must be thought out before simply typing 'mls qos' and expecting everything to work as before.

If you can post what you are trying to achieve with QoS then we can maybe help you more, otherwise if you don't need qos leave it turned off.

Andy

 

[PHead2]

Well, like I said I am using the auto qos settings for VoIP:

mls qos map cos-dscp 0 8 16 26 32 46 48 56
mls qos srr-queue input bandwidth 90 10
mls qos srr-queue input cos-map queue 1 threshold 2 1
mls qos srr-queue input cos-map queue 1 threshold 3 0
mls qos srr-queue input cos-map queue 2 threshold 1 2
mls qos srr-queue input cos-map queue 2 threshold 2 4 6 7
mls qos srr-queue input cos-map queue 2 threshold 3 3 5
mls qos srr-queue input dscp-map queue 1 threshold 2 9 10 11 12 13 14 15
mls qos srr-queue input dscp-map queue 1 threshold 3 0 1 2 3 4 5 6 7
mls qos srr-queue input dscp-map queue 1 threshold 3 32
mls qos srr-queue input dscp-map queue 2 threshold 1 16 17 18 19 20 21 22 23
mls qos srr-queue input dscp-map queue 2 threshold 2 26 33 34 35 36 37 38 39
mls qos srr-queue input dscp-map queue 2 threshold 2 48 49 50 51 52 53 54 55
mls qos srr-queue input dscp-map queue 2 threshold 2 56 57 58 59 60 61 62 63
mls qos srr-queue input dscp-map queue 2 threshold 3 24 25 27 28 29 30 31 40
mls qos srr-queue input dscp-map queue 2 threshold 3 41 42 43 44 45 46 47
mls qos srr-queue output cos-map queue 1 threshold 3 5
mls qos srr-queue output cos-map queue 2 threshold 3 3 6 7
mls qos srr-queue output cos-map queue 3 threshold 3 2 4
mls qos srr-queue output cos-map queue 4 threshold 2 1
mls qos srr-queue output cos-map queue 4 threshold 3 0
mls qos srr-queue output dscp-map queue 1 threshold 3 40 41 42 43 44 45 46 47
mls qos srr-queue output dscp-map queue 2 threshold 3 24 25 26 27 28 29 30 31
mls qos srr-queue output dscp-map queue 2 threshold 3 48 49 50 51 52 53 54 55
mls qos srr-queue output dscp-map queue 2 threshold 3 56 57 58 59 60 61 62 63
mls qos srr-queue output dscp-map queue 3 threshold 3 16 17 18 19 20 21 22 23
mls qos srr-queue output dscp-map queue 3 threshold 3 32 33 34 35 36 37 38 39
mls qos srr-queue output dscp-map queue 4 threshold 1 8
mls qos srr-queue output dscp-map queue 4 threshold 2 9 10 11 12 13 14 15
mls qos srr-queue output dscp-map queue 4 threshold 3 0 1 2 3 4 5 6 7
mls qos queue-set output 1 buffers 20 20 20 40

On each port with a phone:

!
interface FastEthernet3/0/1
switchport trunk native vlan 9
switchport voice vlan 100
no ip address
srr-queue bandwidth share 10 10 60 20
srr-queue bandwidth shape 10 0 0 0
mls qos trust device cisco-phone
mls qos trust cos
no mdix auto
auto qos voip cisco-phone
spanning-tree portfast
!

 

[ADB100]

And the configuration for the Gig uplinks?

 

[PHead2]

Right now there are 3 - 3750 swithces using the stackwise connectors so there aren't any uplinks to other switches. There is one 24 port switch with all gigabit interfaces, one 48 port (non-gigabit) and one 24 port with PoE (non-gigabit). Eventually there will be another 3750 switch connected using a fiber uplink and I plan on using the "auto qos voip trust" configuration on any ports that will be used for uplinks (on both ends) with all of the other qos settings being the same on the remote switch.

As for servers/clients connected to other ports (fast ethernet or gigabit) there are no qos settings specified unless there is (or is going to be) a phone plugged into the port. My understanding is that if no qos settings are specified on the port all traffic will automatically be assigned a CoS and DSCP value of zero, which should be fine.

The thing I really don't understand is why is the inter-VLAN traffic being handled differently than intra-VLAN traffic and why the transmission speed is slow only when the transmission is from a host on a gigabit port to a host on a fast ethernet port...

 

[PHead2]

Just to furhter clarify none of the hosts with gigabit connections have any qos settings specified on the ports they are connected to (there will not be a phone there) and I tried testing with hosts that were both connected via a cisco phone (with the port set as specified, the native vlan can varies from port to port) as well as hosts connected directly to the switch. In the case of the hosts being directly connected to the switch there are no qos commands applied to those interfaces, the only configuration of note on those ports is a "switchport access vlan x" command.