C
HAPTER
4
QoS Support on the Catalyst
5000 Family of Switches
This chapter discusses QoS feature support on the Catalyst 5000 Family of switches. The
Catalyst 5000 Family of switches supports only a small subset of QoS features.
Furthermore, QoS feature support on these switches has important hardware and configuration
restrictions. This chapter discusses all the restrictions and configuration requirements for
implementing QoS on the Catalyst 5000 Family of switches and provides command refer-
ences, examples, and a case study. Specifically, this chapter covers the following topics:
•
QoS Architectural Overview
• Enabling Qos Features
•
Input Scheduling
•
Classification
• Marking
•
Congestion Avoidance
•
Case Study
Upon completion of this chapter, you will understand the restrictions surrounding QoS
feature support on the Catalyst 5000 Family of switches and be able to configure the
switches for packet classification, marking, and congestion avoidance.
Catalyst 5000 Family of Switches QoS Architectural
Overview
The Catalyst 5000 Family of switches forwards frames strictly based on MAC address and
VLAN ID. To route frames with a Catalyst 5000, the switch requires a router module, either
a Route Switch Module (RSM) or a Router Switch Feature Card (RSFC). Catalyst 5000
switches with a NetFlow Feature Card or NetFlow Feature Card II (NFFC or NFFC II,
respectively), router module, and specific line modules can perform multilayer switching
(MLS). MLS enables the RSM or RSFC to offload the Layer 2 rewrite functionality of
routers to hardware components on the supervisor engine and line cards. In relation to QoS
functionality, MLS-enabled switches handle QoS packet rewrites slightly different than do
switches without MLS enabled. Because of the system architecture deployed on the
96 Chapter 4: QoS Support on the Catalyst 5000 Family of Switches
Catalyst 5000 Family of switches, these switches support the following QoS features in
specific hardware configurations:
• Classification of untagged frames
•
Trusting of tagged frames
•
Class of service (CoS) rewrite based on destination MAC and VLAN ID or ingress port
• CoS and type of service (ToS) rewrite based on access-control entries (ACEs)
• Output scheduling using one queue with four thresholds
For supporting QoS in network designs, especially networks delivering Voice over IP
(VoIP) or using DiffServ codepoint (DSCP) for differentiated service, the preferred
switches are the Catalyst 6500 Family of switches, the Catalyst 4000 IOS Family of
switches, the Catalyst 3550, or the Catalyst 2950. By today’s standards, the Catalyst 5000
Family of switches is a legacy product and does not support the features necessary for end-
to-end QoS implementations. Furthermore, Cisco Systems, Inc., no longer sells the
Catalyst 5000 Family of switches. Nonetheless, a large number of networks still use the
Catalyst 5000 Family of switches; therefore, network designs need to exploit the QoS
features available on these switches. Figure 4-1 illustrates a sample network design using a
Catalyst 5500 switch in the core layer. The Catalyst 5500 switches include a router module
for Layer 3 routing and the RSMs utilize HSRP for router redundancy. The Catalyst 5500
switches connect Layer 2 to the Catalyst 4000 CatOS switches used as access layer
switches. Generally, legacy networks deploying Catalyst 5500’s only utilize Layer 3
routing in the core. As a result, these networks only connect Layer 2 to access layer switches
and perform no routing of traffic on the access layer switches. Although not shown on the
diagram, several VLANs are deployed in this topology to minimize broadcast domains.
Figure 4-1 Sample Network Topology Using Catalyst 5000 Switches
Catalyst 5500
with RSFC
L2 L2L2
L2
Catalyst 5500
with RSM
Catalyst 2900XLCatalyst 4006
Catalyst 5000 Family of Switches QoS Architectural Overview 97
Software Requirements
The Catalyst 5000 Family of switches requires CatOS software version 5.1(1) or higher for
QoS feature support. The Catalyst 5000 Family of switches runs CatOS software up to
CatOS software version 6.4. The Catalyst 5000 Family of switches does not support Native
IOS software or the CatOS software version 7 train.
MLS changes the behavior of QoS on the Catalyst 5000 Family of switches. MLS support
on the Catalyst 5000 Family of switches requires a NFFC and a Cisco router running Cisco
IOS Software version 11.3 WA, 12.0, or higher. The recommended routers for deploying
MLS are the RSMs or RSFCs. The RSM is a line module for the Catalyst 5000 Family, and
the RSFC is a daughter card for the Catalyst 5000 Supervisor IIG and IIIG engines.
External routers including the Cisco 3600, 7200, and 7500 support MLS as well and are
alternatives to using the RSM or RSFC for MLS.
Hardware Requirements
Only a limited subset of the Catalyst 5000 Family of switches supports QoS features. To
enable these QoS features, an NFFC II must be present on the supervisor engine. EARL 3
and NFFC II are the same hardware component, and the names are used interchangeably.
EARL is an acronym for the Layer 2 forwarding logic on the supervisor engine and exists
in several versions across all the Catalyst supervisor engines of the Catalyst 5000 Family.
The NFFC II enables QoS support for classification, marking, and congestion avoidance.
The Supervisor IIIG and IIG include an NFFC II, whereas specific models of the Supervisor
Engine III include the NFFC II. Table 4-1 illustrates which supervisor engines include an NFFC
II. The Supervisor Engine IIIs without an NFFC II are upgradeable to include an NFFC II.
Table 4-1 NetFlow Feature Card II to Supervisor Engine Matrix
Model Number Supervisor Engine
NetFlow
Feature
Card
EARL
Version
EARL
Subtype
Model
QoS
Feature
Support
WS-X5550 Supervisor IIIG NFFC II EARL 3 WS-F5531 Yes
WS-X5540 Supervisor IIG NFFC II EARL 3 WS-F5531 Yes
WS-X5534 Supervisor IIIF n/a EARL 1++ WS-F5520 No
WS-X5530-E3 Supervisor III (NFFC II) NFFC II EARL 3 WS-F5531 Yes
WS-X5530-E3A Supervisor III (NFFC II-A) NFFC II-A EARL 3 WS-F5531A Yes
WS-X5530-E2 Supervisor III (NFFC) NFFC EARL 2 WS-F5521 No
WS-X5530-E2A Supervisor III (NFFC A) NFFC EARL 2 WS-F5521A No
WS-X5530-E1 Supervisor III n/a EARL 1++ WS-F5520 No
continues
98 Chapter 4: QoS Support on the Catalyst 5000 Family of Switches
Example 4-1 demonstrates use of the show module command to determine the supervisor
engine model number, the EARL version subtype model, and NFFC type for a Catalyst
5000 Family of switches.
Example 4-1 shows sample output from a Supervisor Engine III with an NFFC II.
Model Number Supervisor Engine
NetFlow
Feature
Card
EARL
Version
EARL
Subtype
Model
QoS
Feature
Support
WS-X5509 Supervisor II n/a EARL 1+ WS-F5511 No
WS-X5506 Supervisor II n/a EARL 1+ WS-F5511 No
WS-X5505 Supervisor II n/a EARL 1+ WS-F5511 No
WS-X5009 Supervisor I n/a EARL 1 WS-F5510 No
WS-X5006 Supervisor I n/a EARL 1 WS-F5510 No
WS-X5005 Supervisor I n/a EARL 1 WS-F5510 No
WS-C2926G Supervisor II n/a EARL 1+ WS-F5511 No
WS-C2926T Supervisor II n/a EARL 1+ WS-F5511 No
WS-C2926GS Supervisor III NFFC II EARL 3 WS-F5531 Yes
WS-C2926GL Supervisor III NFFC II EARL 3 WS-F5531 Yes
WS-C2902 Supervisor I n/a EARL 1 WS-F5520 No
WS-C2901 Supervisor I n/a EARL 1 WS-F5520 No
Example 4-1 Sample Output from the show module Command
Console> (enable) show module
Mod Slot Ports Module-Type Model Sub Status
--- ---- ----- ------------------------- ------------------- --- --------
1 1 2 100BaseFX MMF Supervisor WS-X5530 yes ok
(text deleted)
Mod Module-Name Serial-Num
(text deleted)
Mod MAC-Address(es) Hw Fw Sw
--- -------------------------------------- ------ ---------- -----------------
(text deleted)
Mod Sub-Type Sub-Model Sub-Serial Sub-Hw
--- -------- --------- ---------- ------
1 NFFC II WS-F5531 0012152468 1.0
1 uplink WS-U5533 0010450920 1.0
Table 4-1 NetFlow Feature Card II to Supervisor Engine Matrix (Continued)
Catalyst 5000 Family of Switches QoS Architectural Overview 99
The output from the show module command indicates not only supervisor engine type,
NFFC, and EARL versions, but also includes software version, MAC addresses, hardware
and firmware revisions, and serial numbers of all line modules in the chassis. For supervisor
engines without an NFFC or NFFC II, the subtype indicates EARL version.
Moreover, QoS feature support requires traffic ingress and egress from specific Catalyst
5000 line modules. Table 4-2 summarizes the modules required for front-panel support of
QoS features.
To obtain supported features per line module from the command-line interface (CLI), use
the following command:
show port capabilities
mod/ports
Example 4-2 shows sample output from the show port capabilities command for the WS-
X5224 and WS-X5234 line modules, respectively. The output from the commands indicate
that the WS-X5224 does not support QoS features, whereas the WS-X5234 supports CoS
and ToS rewrite as well as output scheduling.
Table 4-2 Required Line Modules for QoS Support
Model No. Description
WS-U5537-FETX 4-port 10/100BASE-TX uplink module
WS-U5538-FEFX-MMF 4-port 10/100BASE-FX uplink module
WS-X5234-RJ45 24-port 10/100BASE-TX RJ-45
WS-X5236-FX-MT 24-port 100BASE-FX MT-RJ
WS-X5239-RJ21 36-port 10/100BASE-TX Telco
Example 4-2 Sample Output from the show port capabilities Command
Console> (enable) ss
ss
hh
hh
oo
oo
ww
ww
pp
pp
oo
oo
rr
rr
tt
tt
cc
cc
aa
aa
pp
pp
aa
aa
bb
bb
ii
ii
ll
ll
ii
ii
tt
tt
ii
ii
ee
ee
ss
ss
22
22
//
//
11
11
Model WS-X5224
Port 2/1
Type 10/100BaseTX
Speed auto,10,100
Duplex half,full
Trunk encap type no
Trunk mode no
Channel no
Broadcast suppression pps(0-150000),percentage(0-100)
Flow control no
Security yes
Dot1x yes
Membership static,dynamic
Fast start yes
QOS scheduling rx-(none),tx-(none)
CoS rewrite no
ToS rewrite no
Rewrite no
continues
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