Cisco Switching/Routing :: Understanding Mls Qos Queue Set Output With 3750

Apr 16, 2012

I've been  working on breaking down and understanding the default auto qos  configuration on a Cisco 3750 in the hopes of putting together a QoS  strategy that will fit our environment.  I'm having some difficulty  understanding how the "mls qos queue-set output" syntax works.
From another post, at [URL], the author offers the following example and explanation;
mls qos queue-set output <1/2> threshold 2 400 400 100 400thresshold 1: 400%
thresshold 2: 400%
thresshold 3: 100% (implicit, not configurable)
reserved: 100%
max: 400%
However, I'm having trouble understanding what is meant.  Here, it looks like it's saying, for example;
mls qos queue-set output 1 threshold 2 400 400 100 400
How  come there is syntax stating "threshold 2" when in the succeeding part  the 400 refers to thresshold 1 and threshold 2 again?  The syntax 400 400 is, apparently, already referring to thresshold 1 and 2, no?

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Cisco Switching/Routing :: 3750 QoS Output Dscp-map Queue Numbering Mis-match?

Feb 16, 2012

When configuring QoS on 3750s/3560s, we're mapping packets to particular interface output queues with commands such as: [code] The command to see what's actually being enqueued, dropped, etc. is: [code]
Note that these queues are numbered 0 - 3, and not 1 - 4.  We've been assuming that the first queue number in the "mls qos" (i.e., 1) command maps to the first queue (i.e., 0) in the "show mls qos" command.

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Cisco Switching/Routing :: Output Queue Drops On 3750 Core Stack And 3560 Edge Switches

Jan 10, 2013

I've been fighting what seems to be an increased number of outqueue drops on our core stack and edge switches for the last 3 or 4 weeks.(The core consists of a stack of 5 3750s in 32-gig stack mode. The wkgrp switches are 3560s. all are at 12.2.52) The  wkgrp switches are directly connected to users. We use Nortel IP phones with the phone inline with the user PC. auto-neg to 100/full. [code] However I have tried turning off QOS on a couple of workgroup switches (no mls qos, but left individual port configurations the same) but am still seeing drops.Since I have disabled qos on the switches in question (no mls qos)  (not the core tho) I am presuming these commands have no affect on the switch operation and therefore cannot be related to the problem. With QOS turned off one would presume that it is general congestion - especially at the user edge where busy PC issues might contribute. So I wanted to see if I could see any instances of packets in the output queues building up.
 I wrote some scripts and macros that essentially did a snapshot of 'show int' every 20 seconds or so, and looked for instances of 'Queue: x/' where x was greater than zero.What I found after several days of watching the core stack, and a few of the workgroup switches that are most often displaying the behavior, was that I NEVER saw ANY packets in output queues. I often saw packets in Input queues for VLAN1, once in a great while I would see packets on input queues for fa or Gi interfaces, but NEVER on output queues. [ code] Additionally, when I look (via snmp) at interface utilization on interfaces showing queue drops (both core and wkgroup), they are occurring at ridiculously low utilization levels (as low as 4 to 8%). I've tried to look for microbursts between the core and a wkgroup switch where the core interface was experiencing drops, but haven't seen any (using observer suite). [code] While the queue-drop counts aren't critically high at this point, they are happening more frequently than in the past and I would like to understand what is going on... In most cases, no error counters are incrementing for these interfaces. Is there some mechanism besides congestion that could cause output queue drops?

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Cisco Switching/Routing :: Large Number Of Queue Output Drops On 6509E

Apr 3, 2013

we have two 6509E, as our core switches. Recently I noticed that on some connections I have a high output queue drop rate.
These 4 x 2 interfaces (gigabit) are connected to our blade encolure, consisting of 4 x WS-CBS3120X-S. The utilization of the links is really quite low, when I see the increase of the drops. (~=60Mbps). All the links are fiber (SFP) and the distance between the core switches and the enclosure is about 15-20m.
I am not aware of any service degradation on the part of the servers. No CRCs, collisions etc, on the interfaces, apart from the drops.
The line card is a WS-X6748-SFP, but other interfaces don't seem to be experiencing any problems.

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Cisco Switching/Routing :: Catalyst 4507r / Queue Usage - QOS - Total Output Drops?

Jan 14, 2013

We're having kind of a problem with our Catalyst 4507r switches. If we do a "show interface" command we're getting a lot of "Total output drops" on some of our interfaces. It seems to be most of the time on the same vlan.I was wondering if it has got something to do with QOS or queue selection As we don't have any QOS markings configured, is it possible that all traffic is using only one of the four tx queue's? 

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Understanding NAT Table And Its Chains (pre-routing / Post-routing And Output)?

May 28, 2011

I'm learning about iptables, but I don't fully understand the chains of NAT table (prerouting, postrouting and output).I'm specially in doubt about prerouting and postrouting. As far as I know, DNAT can be made with prerouting and SNAT can be made with postrouting, so I think prerouting is for input and postrouting is for output, but the material I'm reading (and another sources) are not clear.

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Cisco Switching/Routing :: 3750 - How To Decide On Which Queue / Threshold To Use

Mar 8, 2012

I am working on a QoS design which I hope to test at some point, but at this stage its from the books.My question is how to decide which queue and threshold to use for video traffic, then lower priority traffic.I understand the shaping and sharing commands, its the queuing and threshold bit I'm not clear on.The plan is to use the priority-queue for EF marked voice, this will be policed on ingress to provide an upper limit to EF traffic levels, then my second priority traffic will be video. Which queue will get serviced first once the priority queue is empty, and how do I decide which threshold to allocate my video traffic to? The document ion is not at all clear, I want to prioritse my traffic in the following order:

1 voice, use the priority queue
2 video, this to get serviced ahead of data, after voice.
3 interactive data
4 Bulk data
5 Best effort
So Q1 settings are ignored due to priority queue. Q2 gets 70%, Q3 25% etc.Is it as simple as putting video into Q2 T1, then interactive data into Q2 T2, will Q2T1 get a higher priority over Q2 T2 once the PQ is serviced?

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Cisco Switching/Routing :: QoS / Queue Drops On 3750 Switches?

Apr 30, 2013

We currently have a  site with a very simple topology that uses a 3750X switch stack for a  collapsed core. Everyday, the users have a conference call and  experience poor voice quality.Its not bad when users call from several  conference phones, but when everyone calls in on individual phones,  there is choppy and almost inaudible voice quality experienced. The  voice traffic flow would be as follows: Phone <-> 3750 switch  <-> Voice GW We  have packet captures showing that RTP packet loss is occuring from the  phone to the voice gateway, but none from the voice gateway to the  phones. We also have drops in the output queues that match drops on the  asics. I can reset the counters and they will be clear until the call,  and then they increment significantly during the call. The voice gateway  and phones are non-Cisco. The switch stack has 6 switches. We are trusting the DSCP settings on the  phones. All the queue drops from the phones are usually in queues 0-3,  but all drops on the voice gateway is in queue 0. Below are the QoS  settings; they are mostly default and we have not changed any queuing,  thresholds, or buffers. Should we specify larger buffers and threshold  for a designated queue and send EF traffic to that queue?
MySwitch#sh mls qos
QoS is enabled
QoS ip packet dscp rewrite is disabled
 Typical Port
trust state: trust dscp


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Cisco Switching/Routing :: 3750 Priority Queue Out Transmit Discards

Dec 13, 2011

After opening up Solarwinds NPM, I noticed that a few of my interfaces had lots of discards (who knows how long it's been sets the counters were reset)
interface GigabitEthernet1/0/25description Etherchannel to MamaCassswitchport trunk encapsulation dot1qswitchport mode trunkswitchport nonegotiatepriority-queue outchannel-group 4 mode on
interface GigabitEthernet2/0/25description Etherchannel to MamaCassswitchport trunk encapsulation dot1qswitchport mode trunkswitchport nonegotiatepriority-queue outchannel-group 4 mode on
interface Port-channel4switchport trunk encapsulation dot1qswitchport mode trunkswitchport nonegotiate,It looks as if priority-queue was configured outbound on these interfaces, could this be the cause of the transmit discards which are now up to 79,835, I just reset the counters on the interfaces a little while ago.
I'm not the best in the world when it comes to QoS, we do have some VoIP phones, but they are only a specific network, and do not travel outside, since there are used mainly for VoIP training. I do know both interfaces are running the default of FIFO.

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Cisco Switching/Routing :: 3750 - SRR-Queue Bandwidth Rate Limit?

Feb 25, 2013

If I have an interface configured as follows (on a Cisco 3750 Switch)
Interface gi 1/0/24
Bandwidth 100000
And then added the following command
srr-queue bandwidth limit 40
Would the result be 40% of the physical 1Gbps interface or 40% of the 100Mbps Bandwidth set under the interface bandwidth command.

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Cisco Switching/Routing :: 3560 And 3750 - Any Way To Check For MLS QoS Input Queue Drops?

Feb 10, 2012

I feel that 3560 and 3750 perform differently with the following two commands:
srr-queue bandwidth shape 5 0 0 0
srr-queue bandwidth limit 50
 On 3750, the bandwidth for queue 1 is limited to 100mbps x 50% / 5 = 10mbps
On 3560, the bandwidth for queue 1 is limited to the smaller value of BW / shape weight and BW x limit%.
Does it sound about right?  is there a way to check for mls qos input queue drops? The show mls qos interface xxx stat only shows the output queue drops. Maybe for some reason the input queue never drops?

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Cisco Switching/Routing :: 3750 Service Policy Output Not Supported

Jan 26, 2009

I have a 3750 switch (c3750-ipbasek9-mz.122-46.SE.bin) were i want to add bandwitdh limit pr. interface, doing the following:
ip access-list extended customer_A
permit ip any any 
class-map match-all BW_10Mbps

When i trie to apply the "service-policy output 10 Mbps" to the interface, it says the service-policy output is not supported on the switch. Is this a software related isue ?

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Cisco Switching/Routing :: 3750 Interface Total Output Drops Incorrect

May 15, 2011

I am seeing Interface output drops that appera to be incorrect.  When I do "Show Interface gi1/0/20", I will get interface output drops of "4294961382".  But, when I do the same command again it shows "0" drops.  Is this a reporting error? I am ruinning c3750-ipservicesk9-mz.122-58.SE.bin on a 3750 stack with 2 switches in the stack. [code]

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Cisco Switching/Routing :: Catalyst 3750 Switch Interface Output Drops

Mar 13, 2013

One of my Catalyst 3750 switch have many out drops, I execute "sh mls qos int g2/0/3 statist" command, there are many output drops in queue3 threshold3. [code]

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Cisco WAN :: 3750X-24T Output Queue Drops

Mar 22, 2013

I have a 3750X-24T in our production environment that is showing very high number of OQD's in the 'show int sum' output for 4 of the Gigabit interfaces; the interfaces are each in a seperate port channel and there are no OQD's for the relevant port channel and there are no output drops showing in the output for the 'sh int' command for each interface.
The following are the OQD's for the relenvant interfaces
Gi1/1/1:     0
Gi1/1/2:     0
Gi1/1/3:     0
Gi1/1/4:     0
Gi2/1/1:     4252879251
Gi2/1/2:     4251090833
Gi2/1/3:     4251754140
Gi2/1/4:     4294942102
Po1:          0
Po2:          0
Po3:          0
P04:          0
Gi1/1/1 and Gi2/1/2 assigned to Po1, and so on.
IOS version: C3750E-IPBASEK9-M 12.2(58)SE2

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Cisco WAN :: Output Queue Errors On 2811 ATM1/0 Interfaces

Jun 6, 2012

We are facing output queue problems on our ATM interfaces. A lot of output queue errors are been shown as below.
Cisco 2811 -> ATM Link -> <-ATM Link <- Cisco 3945 Routers.
Cisco 2811 Version is 124-15.T9.bin
Cisco 3945 Version is SPA.150-1.M1.bin
Cisco 2811 Output Errors

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Cisco Switching/Routing :: Understanding Existing Setup With Two 3750s

Jan 10, 2013

We've recently inherited a platform with little handover and also minimal networking experience.We're going 100 miles an hour in learning, but I'm a bit confused with the idea of a L2 switch with no IP assignments to ports, so using VLANs, and a L3 switch with IP assignments. And the combination of both.We have 2 Cisco 3750 switches, along with a whole host of other hardware, so we're starting at this "gateway" to start breaking things down.

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Cisco Switching/Routing :: QoS Priority Queue On Cat 6509?

May 2, 2013

I need to trust and prioritize voip traffic on my 6509 core
at the moment I have mls qos trust dscp on the interface
Is this enough? or do I need to enable the priority queue? how do i do this ? as it doesnt accept the priority queue out command like a normal switch

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Cisco Switching/Routing :: 3560 TX-queue Buffer Sizes

May 29, 2013

We're having some issues with a 3560 CPE. It's uplink is a GE fiber link, customer port is FE RJ45. We see a lot of TX-frames being dropped at the FE port,but none at the GE port. Even when the customer is only at ~50Mbit/s downstream traffic. When customer sending ~50Mbit/s upstream, there are no TX- drops at the GE link. Is this a normal behaviour? From what I know the physical medium shouldn't have any inpact on this since drops occurs in the port- asic, and not in physical transmission.Do the buffer-sizes between GE and FE differ? What could we do to optimize the flow and reduce drops? QoS is set to off and no modifications on the queues have been made on the interfaces.

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Cisco Switching/Routing :: 3550 Won't Accept WRR-Queue Commands

Jan 22, 2013

We are upgrading from 3550 - 3560 switches.On the 3550's we have this on each interface: [code] The 3550's wont accept the wrr-queue commands. How to set these on the 3560's.

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Cisco Switching/Routing :: 2921 - Queue-limit With Shaping

Mar 8, 2012

I have a 2921 where I am shaping some traffic based on sub net on my lan.  I have applied the shaping policy to the lan interface in the outgoing direction.
Topology is as follows:  
Policy map: 
Policy Map shape-lan
I am seeing a lot of no-buffer drops on the policy and I am wondering what the best solution is to solve this: 
Class-map: tc-class (match-any)
   8730680 packets, 10803689863 bytes
   5 minute offered rate 4453000 bps, drop rate 0 bps
Should I just be increasing the queue-limit or should I be changing something else?

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Cisco Switching/Routing :: 6500 QoS Not Enabling Rcv-queue Defaults

Feb 20, 2013

One one of our Cisco 6509s I've globally enabled QoS and set a port to "trust cos". However when I look at the queueing for that interface, I notice that the receive queue thresholds have not changed to the default.
I'm kind of new to QoS so I'm not sure if I'm missing something.
We are using a Cisco 6509 running 12.2(33)SXI3 using the WS-X6724-SFP card. I thought I'd be seeing the default tail-drop thresholds, but instead I still see the defaults as if QoS were not enabled:
Queueing Mode In Rx direction: mode-cos
Receive queues [type = 1q8t]:
Queue Id    Scheduling  Num of thresholds


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Cisco Switching/Routing :: Packet Drops On Queue On 6509 Even Though QOS Is Disabled

Mar 9, 2013

I can see drops on the 6509 Queue for interface gi1/6 , qos is disabled globaly with qos disabled all packets are in one Queue using best effort my question is if I can see drops using the sh queueing int Gi1/6 command  why I am not seeing any drops when I run the Sh int (interface number )  command. [code]

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Cisco Switching/Routing :: 3750E ACL Marked Traffic Are Not In Correct Queue

Apr 22, 2012

We tested a QoS in a Cisco 3750E, IOS: 12.2(58)SE2.Voice traffice in the correct Q without any problem, but all the others traffic the Defualt Q (0), tried to capture the traffic and tcp/udp port are correct.Any thing wrong with my ACL or DSCP - CoS?? ( that ACL works fin on 4500 and 6500) [code]

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Cisco Switching/Routing :: 2960G Disable Srr-queue On Switch Port

Jun 20, 2012

I have a Cisco 2960G switch and one of the ports was configured with srr-queue bandwidth limit 90 - I need to remove this bandwidth limiting from this interface. [code]

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Cisco Switching/Routing :: Input Queue Drops On Vlan 6500

Sep 8, 2012

I can  see drops on one of our busy L3 vlan in the input queue and are going up very frequently.System image file is "sup-bootflash:s72033-psv-mz.122-18.SXD3.binHardware  =  6509

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Cisco Switching/Routing :: Packet Dropped Due To Input Queue Full On 6509

Nov 9, 2011

i have issues logging into one of our core switches.its a 6509 switch but i cannot log in remotely.when i try to console in on the console port, i cannot log in instead i get the above error message.I haven't rebooted yet but would it solve the problem as this switch is a production switch.

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Cisco Switching/Routing :: 2960 - Enabled With Additional Priority-queue Out Command?

Feb 20, 2012

I have a Cisco Catalyst 2960 with IOS Release12.2(53)SE (because of a contract I can not update it) ->  the release notes for this version describe the following:

When auto-QoS is enabled on the switch, priority  queuing is not enabled. Instead, the switch uses shaped round robin  (SRR) as the queuing mechanism. The auto-QoS feature is designed on each  platform based on the feature set and hardware limitations, and the  queuing mechanism supported on each platform might be different. There  is no workaround. (CSCee22591)
My config is as follows:

interface FastEthernet0/1 switchport access vlan 200 switchport mode access srr-queue bandwidth share 10 10 60 20 priority-queue out mls qos trust dscp auto qos voip trust no cdp enable network-policy 1 spanning-tree portfastMy question now is:When the priority queue is not enabled with auto-qos because of the software bug is it nevertheless enabled with the additional priority-queue out command?

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Cisco Switching/Routing :: 2960S - Default Queue / Buffer Settings When MLS QoS NOT Enabled

Feb 13, 2013

I have a customer that is seeing output drops on a 2960S with mls qos not enabled.  It appears that they are getting bursts traffic on the switch that is filling up the buffers, hence causing the drops.  I have a couple of questions:
1. What are the default queue/buffer settings when mls qos is NOT enabled on the switch.
2. Is there any good documentation out there regarding the buffer sizes of the different switch models
The customer is looking for an answer as to whether or not replacing the 2960S with a higher model would eliminate the output drops WITHOUT having to mess with QOS/buffer/drop threshold settings on the switch, and Cisco doesn't seem to make the buffer sizes readily available for the the smaller Catalyst switches.

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Cisco Switching/Routing :: 3560 - Configuring Qos / Traffic To Go Into High Priority Queue

Nov 19, 2012

i have a 3560 connecting to a sp with limited bandwidth. i have one interface on the switch whose traffic i do not want to drop. i want this traffic to go into the high priority queue. i am not sure how this should be configured, but here is my best guess and my current qos configuration on the switch:
qos map cos-dscp 0 8 16 26 32 46 48 56
mls qos srr-queue output cos-map queue 1 threshold 3 5
mls qos srr-queue output cos-map queue 2 threshold 1 4 6 7
mls qos srr-queue output cos-map queue 2 threshold 2 3(code)
since cos 5 is mapped to dscp 46 then this traffic would go into the priority queue. is this correct ?

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Cisco Switching/Routing :: 6509 Configure QoS On Gig Line Cards That Have 1P3Q8T Queue Structure

Nov 3, 2011

I previously put this is the 'Video over IP' discussions group, which is not getting any response.I have a 6509 and need to configure QoS on gig line cards that have 1P3Q8T queue structure. I've already got the mls qos configured, and have the correct class maps built for Voice, Video, and Signalling.(I'm not doing autoqos). I have only four classes; voice, video, signalling, and default (best effort).I need to configure the commands on the individual gig ports for the appropriate bandwidths as shown below:
1. 300 VoIP G711 calls x 100kbs/call = 30mbs of priority queue  DSCP = EF (46) CoS = 5
2. 150 Video conference calls x 1.5mbs/call = 225mbs  DSCP = CS4 (32) CoS = 4
3. 450 Signalling x 13kps/call = 5.8mbs (round to 6mbs) DSCP = CS3 (24) CoS = 3
4. Default class is not marked  DSCP & CoS = 0

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Cisco Switching/Routing :: 4500 Sup6E Priority Queue On Port-channel Member?

Mar 18, 2010

I am trying to implement priority queuing (LLQ) on a pair of 10GE links between a 4507 with Sup6E and a 4948 which are configured as an etherchannel. I am unable to configure a priority queue on the 4507.  I am running into the following issues:
I want to have a priority queue for voice traffic and specify minimum bandwidth for a critical application. If I configure a class with the priority command it will not let me use the bandwidth command on another class unless the priority class is policed. If I try it without the police command I get the message "bandwidth kbps/percent command cannot co-exist with strict priority in the same policy-map ". If I add  a police statement to the priority class then I don't get this error. 

When I try to apply the resulting service-policy to the physical interface it says "% A service-policy with non-queuing actions should be attached to the port-channel associated with this physical port" and does not add the command to the config. 

If I try to associate the same policy-map to the port-channel rather than the physical interface it says "% A service-policy with queuing actions can be attached in output direction only on physical ports" and does not add the command to the config. 
All of the other interfaces on the 4500 are working OK. The trunks have auto qos voip trust configured and access ports are marking the critical application traffic.
The 4507 is running 12.2(44)SG1 EnterpriseK9. I don't have the luxury to upgrade blindly to fix the problem unless I can identify a specific bug that is causing the problem.

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Cisco Switching/Routing :: 2921 / Catalyst 3560 - Router Interface Input Queue Drops?

Nov 6, 2011

i have an 2921 connected to an Catalyst 3560. My router interface shows quite a lot of input queue drops. Load is not too much max 5/255.

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