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4500 remarking dscp value 1 to 0

By rockingoa ·

I am getting a very strange problem where 4500 switch is remarking the packet with dscp 1 to 0.

Let me explaint the setup. I have two PCs connected on same switch but on different modules. PC1 is conencted to Gi4/19 and PC2 is connected to
Gi2/43. Both the ports has been configured to trust the dscp. Below are the configuration:

interface GigabitEthernet4/19
switchport access vlan 6
switchport mode access
qos trust dscp
no snmp trap link-status
spanning-tree portfast

interface GigabitEthernet2/43
switchport access vlan 6
switchport mode access
qos trust dscp
no snmp trap link-status
spanning-tree portfast

When I set the DSCP value 1 on PC1, it reaches PC2 as 0. When I mark the traffic with AF21 or AF11, it reaches PC2 with correct value.

Below the hardware details:

Chassis Type : WS-C4506

Mod Ports Card Type Model .
1 2 Supervisor IV 1000BaseX (GBIC) WS-X4515
2 48 10/100/1000BaseT (RJ45) WS-X4448-GB-RJ45
4 48 10/100/1000BaseT (RJ45) WS-X4448-GB-RJ45

Switch#sh ver
Cisco IOS Software, Catalyst 4500 L3 Switch Software (cat4500-IPBASEK9-M), Version 12.2(31)SGA1, RELEASE SOFTWARE (fc3)
Technical Support:
Copyright (c) 1986-2007 by Cisco Systems, Inc.
Compiled Fri 26-Jan-07 14:35 by kellythw
Image text-base: 0x10000000, data-base: 0x115C5630

ROM: 12.2(20r)EW1
Dagobah Revision 95, Swamp Revision 29

stfo-db-s01 uptime is 4 years, 15 weeks, 1 day, 16 hours, 4 minutes
System returned to ROM by power-on
System restarted at 15:30:21 met Fri Feb 6 2009
System image file is "bootflash:cat4500-ipbasek9-mz.122-31.SGA1.bin

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Repost as 'Q&A'

by HAL 9000 Moderator In reply to 4500 remarking dscp value ...

Try reposting this in the 'Q&A' forum. The 'Discussion' forum is for matters of general discussion, not specific problems in search of a solution. The 'Water Cooler' is for non-technical discussions. You can submit a question to 'Q&A' here:;content

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