Cisco CATALYST 4000 32 PORT 10/100 L3 MODULE WITH 2 PORT GBIC 规格指南
2w4d: Loading Shared CAM ISL ucode image on [FastEthernet6]No active
members in this bvi, shutting down
2w4d: %STANDBY-6-STATECHANGE: Standby: 2: BVI2 state Standby -> Init
2w4d: Downloading micro code on [FastEthernet8].
2w4d: %LINK-3-UPDOWN: Interface FastEthernet2, changed state to up
2w4d: %LINK-3-UPDOWN: Interface FastEthernet1, changed state to up
members in this bvi, shutting down
2w4d: %STANDBY-6-STATECHANGE: Standby: 2: BVI2 state Standby -> Init
2w4d: Downloading micro code on [FastEthernet8].
2w4d: %LINK-3-UPDOWN: Interface FastEthernet2, changed state to up
2w4d: %LINK-3-UPDOWN: Interface FastEthernet1, changed state to up
!--- Output suppressed.
Q. Can the rate-limiting feature be used on ports configured to be in a bridge
group?
group?
A. Yes, rate-limiting can be applied to any physical ports; however, it cannot be applied
to any virtual interfaces.
to any virtual interfaces.
Q. Can the Access Control Lists (ACLs) or class maps be used to define the traffic
that needs to be rate-limited or shaped?
that needs to be rate-limited or shaped?
A. No, ACLs or class maps are not supported with rate-limiting. All traffic, except the
process-switched or CPU-bound traffic, is subjected to the rate-limiting or shaping on
the interface to which it is applied, in the direction specified.
process-switched or CPU-bound traffic, is subjected to the rate-limiting or shaping on
the interface to which it is applied, in the direction specified.
Q. Can the input rate-limiting and output rate-limiting be applied on the same
interface?
interface?
A. Yes, however, output traffic shaping and output rate-limiting cannot be applied on
the same interface.
the same interface.
Q. Do Layer 3 (L3) Catalyst switches support asymmetrical ingress and egress rate-
limiting?
limiting?
A. Yes, you can specify different rates in each direction in the per-port rate-limiting QoS
configuration.
configuration.
Q. Why is it that, when I issue the show interface fastethernet x rate-limit
command, I get no output?
command, I get no output?
A. The show interface fastethernet x rate-limit command is a generic Cisco IOS
command; it is not supported on the Catalyst Layer 3 (L3) switches because the rate-
limiting is being done on the microcode level. Traffic shaping is done on the traffic that
is going out of a port. In this case, the output of the show interface command can be
used to obtain information about the rate obtained after shaping. Similarly, for egress
rate-limit, the show interface command can be used. For ingress rate-limiting, switches
do not have any counters on the port to check the final rate received. To check the
conformance of the feature, you need to set up the traffic to go out through another port
and see the output counters on that port. For example, the traffic enters from port Fast
Ethernet 1 and leaves through Fast Ethernet 2. To determine the ingress rate obtained
from the rate-limit on Fast Ethernet 1, you need to see the output rate obtained on Fast
Ethernet 2. The other option is to use monitoring tools to see the rate obtained.
command; it is not supported on the Catalyst Layer 3 (L3) switches because the rate-
limiting is being done on the microcode level. Traffic shaping is done on the traffic that
is going out of a port. In this case, the output of the show interface command can be
used to obtain information about the rate obtained after shaping. Similarly, for egress
rate-limit, the show interface command can be used. For ingress rate-limiting, switches
do not have any counters on the port to check the final rate received. To check the
conformance of the feature, you need to set up the traffic to go out through another port
and see the output counters on that port. For example, the traffic enters from port Fast
Ethernet 1 and leaves through Fast Ethernet 2. To determine the ingress rate obtained
from the rate-limit on Fast Ethernet 1, you need to see the output rate obtained on Fast
Ethernet 2. The other option is to use monitoring tools to see the rate obtained.
Q. Why is it that I get a lower performance for TCP traffic with rate-limiting?
A. TCP applications behave poorly when packets are dropped as a result of rate-
Page 4 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