General Guidelines - Cisco 7604 Configuration Manual

Chapter 41 Configuring PFC QoS

General Guidelines

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OL-4266-08
Configure the same trust mode on all ports supported by an ASIC. Mismatched trust modes cause
inconsistent bandwidth and queue-limit ratios.
The match ip precedence and match ip dscp commands filter only IPv4 traffic.
In Release 12.2(18)SXE and later releases, the match precedence and match dscp commands filter
IPv4 and IPv6 traffic.
In Release 12.2(18)SXE and later releases, the set ip dscp and set ip precedence commands are
saved in the configuration file as set dscp and set precedence commands.
In Release 12.2(18)SXE and later releases, PFC QoS supports the set dscp and set precedence
policy map class commands for IPv4 and IPv6 traffic.
The flowmask requirements of QoS, NetFlow, and NetFlow data export (NDE) might conflict,
especially if you configure microflow policing.
With egress ACL support for remarked DSCP and VACL capture both configured on an interface,
VACL capture might capture two copies of each packet, and the second copy might be corrupt.
You cannot configure egress ACL support for remarked DSCP on tunnel interfaces.
Egress ACL support for remarked DSCP supports IP unicast traffic.
Egress ACL support for remarked DSCP is not relevant to multicast traffic. PFC QoS applies ingress
QoS changes to multicast traffic before applying egress QoS.
NetFlow and NetFlow data export (NDE) do not support interfaces where egress ACL support for
remarked DSCP is configured.
When egress ACL support for remarked DSCP is configured on any interface, you must configure
an interface-specific flowmask to enable NetFlow and NDE support on interfaces where egress ACL
support for remarked DSCP is not configured. Enter either the mls flow ip
interface-destination-source or the mls flow ip interface-full global configuration mode
command.
Interface counters are not accurate on interfaces where egress ACL support for remarked DSCP is
configured.
You cannot apply microflow policing to IPv6 multicast traffic.
You cannot apply microflow policing to traffic that has been permitted by egress ACL support for
remarked DSCP.
Traffic that has been permitted by egress ACL support for remarked DSCP cannot be tagged as
MPLS traffic. (The traffic can be tagged as MPLS traffic on another network device.)
When you apply both ingress policing and egress policing to the same traffic, both the input policy
and the output policy must either mark down traffic or drop traffic. PFC QoS does not support
ingress markdown with egress drop or ingress drop with egress markdown. (CSCea23571)
If traffic is both aggregate and microflow policed, then the aggregate and microflow policers must
both be in the same policy-map class and each must use the same conform-action and
exceed-action keyword option: drop, set-dscp-transmit, set-prec-transmit, or transmit.
You cannot configure PFC QoS features on tunnel interfaces.
PFC QoS does not rewrite the payload ToS byte in tunnel traffic.
PFC QoS filters only by ACLs, dscp values, or IP precedence values.
Cisco 7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX
PFC QoS Configuration Guidelines and Restrictions
41-51