Brocade FastIron Ethernet Switch Traffic Management Guide - Manual (Page 32)

Prior to 08.0.00, the only way to prevent such threats was to mark all packets using ACLs. Beginning
with 08.0.00, the internal forwarding priority can be set using an ACL only for flows that require
preferential QoS treatment. For all other flows, you can remark DSCP and CoS fields globally. Traffic
marked by the ACL method always has a higher priority than the global marking.
When DSCP marking is configured on a given port, the DSCP field of any IPv4 packet received on the
port is remarked to the configured value.
When CoS marking is configured, the PCP bit value in the VLAN header is remarked to the desired
value for all tagged packets. CoS marking can be configured on a port. When configured on a port, the
PCP bit in the VLAN header for all packets that egress the port is remarked to the configured value.
Both DSCP and CoS global marking can be configured on the ports of the modules that are configured
but not physically present. When the modules are hot-swapped, the marking is automatically applied
or removed.
The DSCP and CoS remarking can be configured through the command-line interface (CLI) at the
global level and the interface level. The global DSCP and CoS marking can coexist with other security
features configured on the same port. The coexistence rules are the same as those for IPv4 ACLs.
Configuration considerations and limitations
• When an ACL is configured on a port without remarking and global DSCP remarking is enabled,
the global DSCP remarking is enabled for the permitted traffic.
• DSCP and CoS global remarking are supported on the same interface together.
• DSCP and CoS global remarking cannot coexist with MAC filters and MAC-based VLANs.
The following table summarizes the behavior when the remarking is set.
DSCP and PCP remarking TABLE 18
DSCP Remarking set Remarking set Not set
CoS Remarking set Not set Remarking set
DSCP action Remark DSCP at the ingress Remark DSCP at the ingress N/A
PCP action Remark PCP at the egress N/A Remark PCP at the egress
Traffic class Apply the TC equivalent to DSCP Apply the TC equivalent to
DSCP
Apply the TC equivalent to
PCP
Enabling DSCP marking
To enable DSCP remarking globally, use the ip dscp-remark command in global configuration mode.
To enable DSCP remarking on a port, use the ip dscp-remark command in interface configuration
mode.
Example: DSCP marking
The following example shows how to set the DSCP value to 3 for all IP packets:
device(config)# ip dscp-remark 3
Configuration considerations and limitations
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