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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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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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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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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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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Jul 18, 2012
I have 2 x 3750 stacked, the port number of the master switch is gigabitEthernet2/0/1, slave as gigabigEtherent1/0/1.
Can I change the port numbering so that the master switch gets GigabitEthernet1/0/x?
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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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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
GigabitEthernet1/0/4
trust state: trust dscp
[code].....
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Mar 14, 2012
I am trying to mark http packets from a web server with DSCP ef, but when I am doing a traffic capture all http packets have tos 0x0.I am able to mark UDP and ICMP packets originated from this server, but not any TCP traffic.The web server is in VLAN 20This is my config mls qos ip access-list extended MARK-HTTP-ACL permit tcp host 10.10.10.10 eq www. [code]
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Dec 24, 2012
i would like to know the possibility to use mls qos trust dscp with service-policy in the IOS ver.12.2(25)SEE2.The specific version is not possible to configure like below.
Cat3750(config-if)#do sh run int f1/0/1
Building configuration...
[code]....
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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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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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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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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
[Code]....
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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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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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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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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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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Jan 30, 2013
How the port numbering would be on Sup 7-E and Sup 7L-E? I mean, on Sup-6E and Sup-6LE, if I used a twin-gig converter, I used ports gi3/3,gi3/4,gi3/5 and Gi3/6 [If the sup is in 3rd Slot]. I know there are now 4 ports on the Sup 7 which can either be used as Gig ports or TenGig ports. So, how will the port numbering change ?
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Apr 2, 2013
blank configuration for WS-C4500X-16SFP+ (Catalyst 4500-X 16 TenGig Fixed ports switch).
I would like to know how the port numbering is done (i.e. TenGig1/0/X or TenGig1/X or just Eth1/0/X ? )
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Jan 17, 2010
I was wondering if a interface numbering scheme is available for the 4900M. Configuration includes 1 x 8Port 10G and 1 x 20Port 1G modules. would like to understand How the slots are addressedInterface AddressingTwinGig interface addressing
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Aug 15, 2012
Concerning the WS-X4640-CSFP-E module, I was surprised to realize when I got it that the ports are numbered 1-80 rather than 1-40. Then I saw it is actually an 80 port blade when you use half-SFP's. But we have full SFP's, so how does it do the numbering? If I use all full-SFP modules, do the even-numbered ports just go unconfigured?
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Apr 10, 2012
Assume I had Catalyst 3560X/3750X with 24 ports. The partnumber is WS-C3560X-24P-LI would like to how is the numbering defined if the switches have a C3KX-NM-10G installed with 4 SFP-GE-L.
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Feb 1, 2013
We are planning for the first installation of 4500 switches containing these supervisor modules. I'm trying to determine the interface numbering convention for ports on the supervisors. Our existing 4500E all have SUP6 modules with twin-gig converters - so I am familiar with the numbering conventions used on those supervisors. How does this change with the software based selection command "hw-module uplink select" used in SUP7?
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Sep 12, 2011
I'm testing QoS with a 3750-X
I want to mark traffic in the 192.168.126.0/24 subnet with DSCP EF.
I've entered this command :
mls qos
class-map match-any class_126
match access-group 2
policy-map mark_dscp_126
[Code]....
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May 15, 2013
I am getting a very strange problem where 4500 switch is remarking the packet with dscp 1 to 0.
Let me explaint the setup. I have two PCs connected on same switch but on different modules. PC1 is conencted to Gi4/19 and PC2 is connected to
Gi2/43. Both the ports has been configured to trust the dscp. Below are the configuration:
interface GigabitEthernet4/19
switchport access vlan 6
switchport mode access
[Code].....
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Jul 21, 2012
i did on cisco 2960S switch at user ingress interface. but the marking is not showing in show policy-map interface gig 1/0/10 interface and ACL is not showing any match.
I also had a config reference from 2960S cisco guide.
access-list 103 permit tcp any any eq 80
access-list 104 permit tcp any any eq 23
access-list 105 permit icmp host 172.24.68.4 any
class-map IN_HTTP
match access-group 103
class-map IN_TELNET
match access-group 104(code)
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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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Jan 29, 2012
I have a pair of Nexus 7K's running 5.1(3). I have a handful of edge devices that I need to mark ingress traffic, and need to mark both DSCP and CoS. Right now, I have a working config that marks DSCP appropriately.While that works dor DSCP, the MQC will not allow me to mark both DSCP and COS in the same class, and unlike IOS, it appears that Nexus does not have a default DSCP-to-COS mapping. My understanding is this can be solved using table maps, but I don't see how that can solve my problem in this specific scenario (it appears I can do marking or table-map mutation, but not both?). How I can accomplish both?
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Sep 6, 2012
there is something I find strange on C6500 about QoS: C6500 derive an internal DSCP value for it's internal use, but when configuring the qos mapping on output interfaces, only a cos value (I guess, an internal cos value) can be used. Is it a misunderstanding from me, or is it really illogic?
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Apr 29, 2012
I've been working on a 3560 that doesn't seem to map dscp values to a new value: mls qos map dscp-mutation ToR1 22 24 to 46
[Code]....
On the router on the other side, I created an acl that matched on dscp 46, but it doesn't match on it. I've tried moving the mutation map to the ingress interface and I've tried setting dscp with a service policy instead of marking COS and using internal dscp. Where is the mutation map supposed to be placed: ingress or egress? Also, I added an entry in the acl on the router to see if I was mapping to dscp 24, and I am:
[Code]....
So it seems like the mutation map is being ignored completely. Any reason why?
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Jul 4, 2012
I am reading through a QOS Document and they want me to trust the DSCP value from an IP phone (Siemens) but UN trust the PC DSCP value. How can I trust one thing but not the other? I am using a 2960 Cisco switch with IP base IOS.
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Jan 8, 2013
i have Catalyst2950SI with iOS12.1, connect a wifi-access-point to f1/1(dot1q trunk port),and connect another L2SW to f1/2(dot1q trunk port),and IP phone, MobileCamera connects to wifi-access-point,IP phone has dscp=40 value on its own packet,but MobileCamera doesn't have any dscp value or cos.now, i wanna do QoS by that dscp, So i type as below,
interface 1/1
switchport mode trunk
mls qos trust dscp
interface 1/2
switchport mode trunk
mls qos trust cos
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