Cisco CATALYST 4000 32 PORT 10/100 L3 MODULE WITH 2 PORT GBIC Specification Guide
supported in the Layer 3 (L3) Catalyst switches?
Do the Layer 3 (L3) Catalyst switches implement any congestion avoidance
mechanisms such as Weighted Random Early Detection (WRED)?
mechanisms such as Weighted Random Early Detection (WRED)?
Do the Layer 3 (L3) Catalyst switches support IEEE 802.1p classification or Class
of Service (CoS) classification?
of Service (CoS) classification?
Is the Layer 2 (L2) Class of Service (CoS) value retained for packets routed
through the WS-X4232-L3 module?
through the WS-X4232-L3 module?
NetPro Discussion Forums - Featured Conversations
Related Information
Introduction
This document addresses Frequently Asked Questions (FAQ) on the Quality of Service (QoS)
features of the Catalyst 2948G-L3, Catalyst 4908G-L3, and WS-X4232-L3 module (line card) for
the Catalyst 4000 switch.
features of the Catalyst 2948G-L3, Catalyst 4908G-L3, and WS-X4232-L3 module (line card) for
the Catalyst 4000 switch.
For more information on document conventions, refer to the
Conventions Used in Cisco Technical
Tips
.
Q. Which QoS features do the Layer 3 (L3) Catalyst switches support?
A. They support input classification based on the IP precedence of the incoming packet,
output scheduling based on Weighted Round-Robin (WRR) scheme, egress policing
(per-port output rate-limiting), ingress policing (per-port input rate-limiting), and output
traffic shaping (per-port).
output scheduling based on Weighted Round-Robin (WRR) scheme, egress policing
(per-port output rate-limiting), ingress policing (per-port input rate-limiting), and output
traffic shaping (per-port).
Q. What is the minimum software required for QoS on the Layer 3 (L3) Catalyst
switches?
switches?
A. The QoS feature of output scheduling based on IP precedence is supported as of the
first Cisco IOS® Software Release 12.0(7)W5(15a). Support of per-port rate-limiting
and output shaping features began with Cisco IOS Software Release 12.0(10)W5(18e).
Cisco IOS Software Release 12.0(10)W5(18e) contains a bug, Cisco bug ID
first Cisco IOS® Software Release 12.0(7)W5(15a). Support of per-port rate-limiting
and output shaping features began with Cisco IOS Software Release 12.0(10)W5(18e).
Cisco IOS Software Release 12.0(10)W5(18e) contains a bug, Cisco bug ID
CSCds82323
(
registered
customers only
) , that can affect rate-limit features. The
problem is fixed in Cisco IOS Software Release 12.0(14)W5(20).
Q. Can the Layer 3 (L3) Catalyst switches mark or rewrite IP precedence Type of
Service (ToS) bits in an IP packet?
Service (ToS) bits in an IP packet?
A. No, but they do honor them and use them for input classification and output
scheduling.
scheduling.
Q. Are there any restrictions on the ports to which the per-port traffic conditioning
can be applied?
can be applied?
A. Yes, you can apply these features only on physical ports (all ports in Catalyst 2948G-
L3 and Catalyst 4908G-L3). Hence, you cannot configure per-port traffic conditioning
features on the virtual interfaces such as Fast EtherChannel (FEC), Gigabit
EtherChannel (GEC), Bridge-Group Virtual Interface (BVI), or subinterfaces. However,
you can apply these features on Layer 2 (L2) bridged ports in addition to the Layer 3
(L3) routed ports.
L3 and Catalyst 4908G-L3). Hence, you cannot configure per-port traffic conditioning
features on the virtual interfaces such as Fast EtherChannel (FEC), Gigabit
EtherChannel (GEC), Bridge-Group Virtual Interface (BVI), or subinterfaces. However,
you can apply these features on Layer 2 (L2) bridged ports in addition to the Layer 3
(L3) routed ports.
Page 2 of 7
Cisco - Catalyst G-L3 Series Switches and WS-X4232-L3 Layer 3 Modules QoS FAQ
7/20/2004
http://www.cisco.com/warp/customer/473/125.html