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Cisco 10000 Series Router Quality of Service Configuration Guide
OL-7433-09
Chapter 7 Marking Traffic
Restrictions and Limitations for Marking
Figure 7-4 Tunnel Header Marking
Feature History for Tunnel Header Marking
Restrictions and Limitations for Marking
DSCP-Based and Precedence-Based Marking
• You cannot simultaneously configure both the set ip dscp command and the set ip precedence
command in a policy map.
• Because IP precedence is actually part of the DSCP value, you cannot simultaneously set both the
IP precedence and DSCP values for a traffic class. A packet can have one value or the other, but not
both. If you do configure both values, the router marks the packet with the DSCP value.
• Because the router copies the IP precedence value to the MPLS EXP bits during label imposition,
you cannot simultaneously set both IP precedence and MPLS experimental marking for a class.
• Marking has no preset scaling limit.
• In Cisco IOS Release 12.3(7)XI, the router accepts the set precedence and set dscp commands
without specifying the ip keyword. However, you must specify the set
ip precedence command to
set the precedence value in a packet header and the set ip dscp command to set the DSCP value. The
ip keyword is required.
Frame Relay DE Bit Marking Restrictions
• In Cisco IOS Release 12.3(7)XI, when you enter the set ? command, the context-sensitive help lists
the fr-de keyword to allow you to set the Frame Relay discard eligibility (DE) bit. However, the
router does not support setting the DE bit in Cisco IOS Release 12.3(7)XI and later releases.
Cisco IOS Release Description Required PRE
Release 12.2(31)SB2 This feature was introduced on the PRE2 to allow you to
mark the outer IP header’s DSCP or precedence value
during tunnel encapsulation of the packet.
PRE2
190190
Tos=abc
Inbound
Interface
Traffic
Tunnel Header Marking
policy-map
Cisco 10008 Router
P2
P1
Packet
headers marked
Tunnel
Outbound
Interface
Tos=xyz
Tos=abc
191282
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