Catalyst+QoS+Simplified+Presentation

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- Carl Sagan

Meet Your Host

Kevin Wallace CCIEx2 (Voice and R/S) #7945 R/S, CCSI #20061

Full-time instructor of Cisco courses Author for Cisco Press Bachelors Degree in Electrical Engineering Worked with Cisco products since 1989 (starting with

a Cisco AGS+ Brouter running Cisco IOS 7.x) Industry experience at:

- Walt Disney World (Network Design Specialist) - Eastern Kentucky University (Network Manager)

WB: Kevins Milk Bottle

Soldering Iron

Milk

Bottle

Kevin

(3 months old)

Cisco Catalyst 3560 vs. 3750

Cat 3560

Cat 3750

Used on the CCIE Routing and Switching lab Standalone version of the Cat 3750 Does not support Cisco StackWise technology

Used on the CCIE Voice lab Supports Cisco StackWise technology

Cisco Catalyst Quality of Service (QoS) Features

Classification and Marking

Policing

Congestion Management

Congestion Avoidance

Classification and Marking

By classifying and marking traffic early, the traffic can avoid being reclassified at every router/switch hop.

Globally Enabling QoS

Classification (and QoS in general) is disabled by default. To enable QoS: SW1(config)#mls qos

Enabling VLAN-Based Classification

Classification can be Port-Based or VLAN-Based. To use the VLAN-based approach, enable VLAN-Based QoS on individual interfaces in the VLAN with the command: SW1(config-if)#mls qos vlan-based

VLAN-Based Classification Example

SW1(config)#interface vlan 100

SW1(config-if)#service-policy input test

SW1(config-if)#exit

SW1(config)#interface gig 1/0/7

SW1(config-if)#mls qos vlan-based

Port-Based Classification Options

CoS Value MAC ACL

IP Precedence Value DSCP Value Layer 3 ACL

Handling Non-IP Traffic

Non-IP Frame

What happens when were trusting a marking in the IP header (e.g. DSCP), but the incoming frame doesnt have an

IP header?

Handling Non-IP Traffic (cont.)

CoS = 3

If the frame has a CoS value, keep it.

CoS = 3

Handling Non-IP Traffic (cont.)

No CoS

If the frame does not have a CoS value, assign the ports CoS value.

CoS = 0

Setting the Ports CoS Value

SW1(config-if)#mls qos cos value

SW1(config-if)#mls qos cos override

Setting the Ports Trust State

SW1(config-if)#mls qos trust ?

cos cos keyword

device trusted device class

dscp dscp keyword

ip-precedence ip-precedence keyword

By default, nothing is trusted.

Setting the Ports Trust State (cont.)

SW1(config-if)#mls qos trust cos

SW1(config-if)#mls qos trust device ?

cisco-phone Cisco IP Phone

SW1(config-if)#mls qos trust device cisco-phone

We can trust a specific marking if, and only if, the marking came from a Cisco IP Phone.

QoS Mappings Once we trust an incoming marking, we can remark that

frame/packet based on a mapping table. SW1#show mls qos maps cos-dscp

Cos-dscp map:

cos: 0 1 2 3 4 5 6 7

--------------------------------

dscp: 0 8 16 24 32 46 48 56

CoS = 3

In this example, if a frame has a CoS value of 3, it will be given a DSCP value of 24.

DSCP = 24

QoS Mappings (cont.) The switch supports multiple mapping tables.

SW1#show mls qos maps ?

cos-dscp cos-dscp map keyword

cos-input-q cos-input queue map keyword

cos-output-q cos-output queue map keyword

dscp-cos dscp-cos map keyword

dscp-input-q dscp-input queue map keyword

dscp-mutation dscp-mutation map keyword

dscp-output-q dscp-output queue map keyword

ip-prec-dscp ip-prec-dscp map keyword

policed-dscp policed-dscp map keyword

| Output modifiers

QoS Mappings Example #1 CoS-to-DSCP Mapping

SW1(config)#mls qos map ?

cos-dscp cos-dscp map: eight dscp values for cos 0-7

dscp-cos dscp-cos map keyword

dscp-mutation dscp-mutation map keyword

ip-prec-dscp dscp values for ip precedences 0 - 7

policed-dscp policed-dscp map keyword

SW1(config)#mls qos map cos-dscp 0 8 16 24 32 46 48 56

SW1(config)#exit

SW1#show mls qos maps cos-dscp

Cos-dscp map:

cos: 0 1 2 3 4 5 6 7

--------------------------------

dscp: 0 8 16 24 32 46 48 56

QoS Mappings Example #2 DSCP Mutation

SW1(config)#mls qos map dscp-mutation DEMO 24 26 28 30 to 24


SW1(config-if)#mls qos trust dscp

SW1(config-if)#mls qos dscp-mutation DEMO

SW1(config-if)#do show mls qos maps dscp-mutation

Dscp-dscp mutation map:

DEMO:

d1 : d2 0 1 2 3 4 5 6 7 8 9

---------------------------------------

0 : 00 01 02 03 04 05 06 07 08 09

1 : 10 11 12 13 14 15 16 17 18 19

2 : 20 21 22 23 24 25 24 27 24 29

3 : 24 31 32 33 34 35 36 37 38 39

4 : 40 41 42 43 44 45 46 47 48 49

5 : 50 51 52 53 54 55 56 57 58 59

6 : 60 61 62 63

Policing

Policing sets a speed limit for traffic. Traffic not exceeding the speed limit is called conforming traffic. Traffic exceeding the speed limit is called exceeding traffic.

Policing (cont.)

Based on whether traffic is conforming or exceeding, it can be: Transmitted Dropped Transmitted and Remarked

Policing can be applied to one of the following: Switch Port SVI

Policing a Switch Port

Traffic can be policed based on: A single class of traffic Multiple classes of traffic A policing configuration that polices multiple classes of traffic is called an aggregate policer.

Policing Example 1 Policing a Single Class of Traffic

This configuration limits VoIP packets to a rate of 256 kbps.

SW1(config)#access-list 100 permit udp any any range 16384 32767

SW1(config)#class-map VOIP

SW1(config-cmap)#match access-group 100

SW1(config-cmap)#exit

SW1(config)#policy-map POLICE-VOIP

SW1(config-pmap)#class VOIP

SW1(config-pmap-c)#police 256000 8000 exceed-action drop

SW1(config-pmap-c)#exit

SW1(config-pmap)#exit


SW1(config-if)#service-policy input POLICE-VOIP

Rate Limit in bps

Burst Size in Bytes

Policing Example 2 Policing Multiple Classes of Traffic

This configuration limits the combined bandwidth of RTP and SCCP to 320 kbps.

SW1(config)#mls qos aggregate-police VOIP-MEDIA-SIGNALING 320000 8000 exceed-action drop

SW1(config)#ip access-list extended RTP

SW1(config-ext-nacl)#permit udp any any range 16384 32767

SW1(config-ext-nacl)#exit

SW1(config)#ip access-list extended SCCP

SW1(config-ext-nacl)#permit tcp any eq 2000 any

SW1(config-ext-nacl)#permit tcp any any eq 2000

SW1(config-ext-nacl)#exit

SW1(config)#class-map RTP

SW1(config-cmap)#match access-group name RTP


SW1(config)#class-map SCCP

SW1(config-cmap)#match access-group name SCCP


SW1(config)#policy-map AGGREGATE

SW1(config-pmap)#class RTP

SW1(config-pmap-c)#police aggregate VOIP-MEDIA-SIGNALING


SW1(config-pmap)#class SCCP

SW1(config-pmap-c)#police aggregate VOIP-MEDIA-SIGNALING




SW1(config-if)#service-policy input AGGREGATE

RTP

SCCP

Aggregate Policing Rule

Policing Example 3 Remarking Traffic Using a QoS Map

This configuration limits uses a policed-dscp mapping (which maps DSCP values of 24, 26, and 46 to a DSCP value of 0) to specify the exceed actions for the

VOICE policy map.

SW1(config)#mls qos map policed-dscp 24 26 46 to 0


SW1(config)#access-list 101 permit tcp any eq 2000 any

SW1(config)#access-list 101 permit tcp any any eq 2000




SW1(config)#class-map SCCP



SW1(config)#policy-map VOICE


SW1(config-pmap-c)#police 256000 8000 exceed-action policed-dscp-transmit


SW1(config-pmap)#class SCCP

SW1(config-pmap-c)#police 32000 8000 exceed-action policed-dscp-transmit




SW1(config-if)#service-policy input VOICE

Policed DSCP Mapping

References the Globally Configured Policed DSCP Mapping

Policing a Switched Virtual Interface (SVI)

Requires a nested policy map.

The policy map applied to the SVI references a policy map that performs the policing.

Policing Example 4 Policing an SVI

SW1(config)#int range gig 1/0/15 - 20

SW1(config-if-range)#mls qos vlan-based

SW1(config-if-range)#exit





SW1(config)#class-map PORTS

SW1(config-cmap)#match input-interface gig 1/0/15 - gig 1/0/20


SW1(config)#policy-map PORT

SW1(config-pmap)#class PORTS

SW1(config-pmap-c)#police 256000 8000 exceed-action drop



SW1(config)#policy-map VLAN


SW1(config-pmap-c)#set dscp 46

SW1(config-pmap-c)#service-policy PORT



SW1(config)#int vlan 100

SW1(config-if)#service-policy input VLAN

Enable VLAN-Based QoS on a Range of Ports

Child Policy Map

Parent Policy Map Nested Child Policy Map

Some Action (Besides Calling Another Policy Map) Must be Specified

This configuration limits RTP traffic Ports Gig 1/0/15 20 to 256 kbps and Marks RTP Traffic with a DSCP Value of Expedited Forwarding (46).

Congestion Management (Queuing)

We have lots of things to configure when it comes to queuing: Defining priority queues Defining a queue set Guaranteeing buffer availability Limiting memory allocation Specifying buffer allocation Setting drop thresholds Mapping CoS and DSCP values to queues Configuring Shaped Round Robin (SRR) Limiting bandwidth on an outbound queue

Ingress Queues

Classification

Policing

Policing

Marking

Marking

Queue 1

Queue 2

Stack Ring

SRR Traffic Into

Switch

Queue 2 (by default) is the priority queue and has 10 percent of the interfaces bandwidth assigned to it.

Egress Queues

Queue 1

Queue 2 Stack Ring SRR

Queue 3

Queue 4

Traffic Out of Switch

No priority queuing is enabled, by default. However, priority queuing can be enabled for Queue 1.

Priority Queue Configuration To change the default input priority queue configuration:

SW1(config)#mls qos srr-queue input priority-queue ?

enter priority queue number [1-2]

SW1(config)#mls qos srr-queue input priority-queue 1 ?

bandwidth ingress priority queue bandwidth % of stack ring

SW1(config)#mls qos srr-queue input priority-queue 1 bandwidth ?

enter bandwidth number [0-40]

SW1(config)#mls qos srr-queue input priority-queue 1 bandwidth 20 ?

SW1(config)#mls qos srr-queue input priority-queue 1 bandwidth 20

TIP: Set the bandwidth to 0 to disable priority queuing.

Priority Queue Configuration (cont.) To enable output priority queuing on Queue 1:

SW1(config-if)#priority-queue out

Congestion Avoidance Weighted Tail Drop (WTD)

Threshold 1 25 percent



CoS 0 - 2

CoS 3 - 4

CoS 5 - 7

Queue Sets

SW1(config-if)# queue-set qset-id

A set of output queuing and WTD parameters can be configured for a queue set.

- WTD Thresholds for a Queue - Guaranteed Buffer Availability for a Queue - Maximum Memory Allocation for a Queue - Buffer Allocation for all Output Queues of an Interface

By default, all ports belong to Queue Set 1. However, ports can be assigned to a second queue set with the following command:

WTD Thresholds, Buffer Availability, and Maximum Memory Allocation

Common Memory Pool

Po

rt 1

- Q

ue

ue

1

Po

rt 1

- Q

ue

ue

2

Po

rt 1

- Q

ue

ue

3

Po

rt 1

- Q

ue

ue

4

Po

rt 2

- Q

ue

ue

1

Po

rt 2

- Q

ue

ue

2

Po

rt 2

- Q

ue

ue

3

Po

rt 2

- Q

ue

ue

4

Each output queue of a port is allocated a specific amount of memory. You can specify what percentage of a queues allocated memory is guaranteed. You can specify the maximum percentage of a queues allocated memory that a queue can have. (NOTE: This can be more than 100 percent. For example, memory can be taken from the common memory pool.)

WTD Thresholds, Buffer Availability, and Maximum Memory Allocation (cont.)

SW1(config)# mls qos queue-set output qset-id threshold queue-id drop-threshold1 drop-threshold2 reserved-threshold maximum-threshold

Common Memory Pool

Po

rt 1

- Q

ue

ue

1

Po

rt 1

- Q

ue

ue

3

Po

rt 1

- Q

ue

ue

4

Po

rt 2

- Q

ue

ue

1

Po

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- Q

ue

ue

2

Po

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- Q

ue

ue

3

Po

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- Q

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ue

4

Po

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2

Queue Set 2 Queue Set 1

In this example, Queue 2 of ports belonging to

Queue Set 2 can allocate 200 percent of the queues allocated

memory, by taking memory from the

Common Memory Pool.

WTD Thresholds, Buffer Availability, and Maximum Memory Allocation (cont.)

SW1(config)# mls qos queue-set output qset-id buffers allocation1 allocation2 allocation3 allocation4

Queue 1 33

Queue 2 17

Queue 3 25

Buffer Allocations for a Ports Four Output Queues

Queue 4 25

The valid buffer allocation range for Queues 1, 3, and 4 is 0 99. The valid buffer allocation range for Queue 2 is 1 100, because Queue 2 contains the CPU buffer.

WTD Thresholds, Buffer Availability, and Maximum Memory Allocation Example 1

SW1(config)#mls qos queue-set output 2 buffers 50 25 10 15

SW1(config)#mls qos queue-set output 2 threshold 2 33 66 100 200


SW1(config-if)#queue-set 2

For Queue Set 2, 50 percent of a ports buffer space is allocated for Queue 1. 25 percent is allocated for Queue 2. 10 percent is allocated for Queue 3. 15 percent is allocated for Queue 4. For Queue Set 2, output Queue 2 (of 4) has its first drop threshold at 33 percent and its second drop threshold at 66 percent. 100 percent of Queue 2s allocated buffer space is guaranteed to be available, if needed. If Queue 2 needs more buffer space, it can borrow from a ports unused buffer space, up to a maximum of 200 percent of Queue 2s buffer allocation. Interface Gig 1/0/11 is being assigned to Queue Set 2.

Mapping QoS Markings to an Output Queue and Drop Threshold

SW1(config)# mls qos srr-queue output [cos-map | dscp-map] queue queue-id threshold threshold-id qos-marking-1 qos-marking-8}

SW1(config)#mls qos srr-queue output cos-map queue 1 threshold 1 0 1


SW1(config)#mls qos srr-queue output cos-map queue 2 threshold 1 4



Queue Threshold CoS

Mapping QoS Markings to an Output Queue and Drop Threshold (cont.)






Queue 1 Queue 2 Queue 3 Queue 4

Threshold 1

Threshold 2

Threshold 3

Cos 0, 1

CoS 2, 3

Cos 4

Cos 5 Cos 6, 7

Setting Thresholds for Input Queues

SW1(config)# mls qos srr-queue input threshold queue-id threshold-percentage1 threshold-percentage2

SW1(config)#mls qos srr-queue input threshold 1 25 50

Similar to the configuration of our output queues, we can set the thresholds for our input queues with the following command:

(Note that queue sets are not used for input queues)

Set the first threshold to 25 percent

of the queue capacity.

Set the second threshold to 50 percent of the

queue capacity.

Queue #1

Buffer Allocation for Input Queues

SW1(config)# mls qos srr-queue input buffers percentage1 percentage2

SW1(config)#mls qos srr-queue input buffers 25 75

Similar to the configuration of our output queues, we can set the buffer allocation for our input queues with the following command:

25 percent of a ports buffers is

given to Queue #1.

75 percent of a ports buffers is

given to Queue #2.

Shaped Round Robin (SRR)

SRR has 2 Modes of Operation Shaped Only available on egress queues. A queue gets a reserves a portion of a ports

bandwidth, and no more.

Shared Available on ingress and egress queues. A queue is guaranteed a portion of a ports

bandwidth, but is not limited to the guaranteed amount.

Bandwidth Allocation for Input Queues (Only Shared Mode is Available)

SW1(config)# mls qos srr-queue input bandwidth weight1 weight2

SW1(config)#mls qos srr-queue input bandwidth 30 70

To give different amounts of bandwidth to our two input queues, we can use the following command:

30 percent of a ports

bandwidth is guaranteed for

Queue #1.

70 percent of a ports

bandwidth is guaranteed for

Queue #2.

TIP: The relative weights to not have to total 100. However, selecting values that do total

100 makes it easier to determine the bandwidth available to each queue.

Bandwidth Allocation for Output Queues (Shared Mode)

SW1(config-if)# srr-queue bandwidth share weight1 weight 2 weight3 weight4

SW1(config-if)#srr-queue bandwidth share 30 20 25 25

Output queues can used either shared or shaped mode. This command is used to configured shared mode and assigns relative queue weights to an

interfaces four output queues.

Relative weight for Queue 1


TIP: The relative weights to not have to total 100. However, selecting values that do total

100 makes it easier to determine the bandwidth available to each queue.



SRR Example 1

SW1(config)#int gig 1/0/4

SW1(config-if)#speed 1000


Determine the amount of bandwidth available to each output queue on interface Gigabit Ethernet 1/0/4.

BW for Q1: [10/(10+25+35+50)] * 1000 Mbps = 83.3 Mbps BW for Q2: [25/(10+25+35+50)] * 1000 Mbps = 208.3 Mbps BW for Q3: [35/(10+25+35+50)] * 1000 Mbps = 291.7 Mbps BW for Q4: [50/(10+25+35+50)] * 1000 Mbps = 416.7 Mbps Total Bandwidth (Mbps) = 83.3 + 208.3 + 291.7 + 416.7 = 1000

Bandwidth Allocation for Output Queues (Shaped Mode)

SW1(config-if)# srr-queue bandwidth shape weight1 weight 2 weight3 weight4

SW1(config-if)#srr-queue bandwidth shape 50 50 0 0

Shaped mode applies a bandwidth restriction (i.e. policing) for a queue. The weight configured is not the relative weight, as it was for shared mode. Rather, the inverse

of the weight (1/weight) determines the shaped bandwidth for a queue.

Inverse weight for Queue 1

Inverse weight for Queue 2

TIP: If a queue is configured for both shared and shaped mode, the shaped mode

configuration is applied.

Shaping not applied to Queue 3

Shaping not applied to Queue 4

SRR Example 2




Determine the amount of bandwidth limits applied to the output queues on interface Gigabit Ethernet 1/0/5.

BW Limit for Q1: 1/30 * 1000 Mbps = 33.3 Mbps BW Limit for Q2: No limit applied BW Limit for Q3: No limit applied BW Limit for Q4: No limit applied

SRR Example 3





Determine the amount of bandwidth guarantees or limits applied to the output queues on interface Gigabit Ethernet 1/0/6.

The shaping config for a queue (i.e. a non-zero value) overrides the sharing configuration. BW Limit for Q1 (Mbps): (1/50) * 1000 = 20 Mbps BW Limit for Q2 (Mbps): (1/50) * 1000 = 20 Mbps BW for Q3: [40/(40+20)] * (1000-20-20) Mbps = 640 Mbps BW for Q4: [20/(40+20)] * (1000-20-20) Mbps = 320 Mbps Total Bandwidth (Mbps) = 20 + 20 + 640 + 320 = 1000 Mbps

Limiting Bandwidth on an Output Interface

SW1(config-if)# srr-queue bandwidth limit weight

SW1(config-if)#srr-queue bandwidth limit 85

This command specifies the maximum amount of an interfaces bandwidth that can be used for outgoing traffic. By default, there is no limit (i.e. a weight of 100).

The interfaces outbound bandwidth is limited to 85 percent of the interface speed.

Verification and Troubleshooting

WARNING! The show policy-map interface command does not show packet/byte counters on a Cisco Catalyst 3750.

To confirm MLS QoS is enabled: show mls qos

SW1#show mls qos

QoS is enabled

QoS ip packet dscp rewrite is enabled

Verification and Troubleshooting (cont.)

To view a ports trust configuration: show mls qos interface interface_id

SW1#show mls qos int gig 1/0/10

GigabitEthernet1/0/10

Attached policy-map for Ingress: TASK1

trust state: not trusted

trust mode: not trusted

trust enabled flag: ena

COS override: dis

default COS: 0

DSCP Mutation Map: Default DSCP Mutation Map

Trust device: none

qos mode: port-based

Verification and Troubleshooting (cont.)

To view an interfaces policer configuration: show mls qos interface interface_id policers SW1#show mls qos int gig 1/0/10 policers

GigabitEthernet1/0/10

policymap=TASK1

type=Single, id=1 rate=128000, qlimit=8000, drop=0

Verification and Troubleshooting (cont.) To view a queue sets parameters: show mls qos queue-set

SW1#show mls qos queue-set

Queueset: 1

Queue : 1 2 3 4

----------------------------------------------

buffers : 10 10 26 54

threshold1: 138 138 36 20

threshold2: 138 138 77 50

reserved : 92 92 100 67

maximum : 138 400 318 400

Queueset: 2

Queue : 1 2 3 4

----------------------------------------------

buffers : 16 6 17 61

threshold1: 149 118 41 42

threshold2: 149 118 68 72

reserved : 100 100 100 100

maximum : 149 235 272 242

Lab Task #1

On switch SW1 interface Gig 1/0/10, you must limit incoming RTP traffic to 128 kbps. Excess traffic should be remarked to a PHB of CS1. Assume that the RTP traffic originated from a Cisco IP Phone.

DEMO

Lab Task #2

On switch SW1 interface Gig 1/0/11 (which is operating at a rate of 1 Gbps), perform the following tasks: Enable the outbound priority queue. Place CoS 4 traffic into Queue 3 Threshold 1. Limit the bandwidth of traffic leaving Queue 2 to 40 Mbps.

DEMO

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Catalyst+QoS+Simplified+Presentation

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