3750 Access Port Question

Aaron Dhiman · ‎08-15-2007

I have a 3750 port configured in Access Mode:

interface FastEthernet1/0/9

switchport access vlan 2

switchport mode access

switchport voice vlan 5

srr-queue bandwidth share 10 10 60 20

srr-queue bandwidth shape 10 0 0 0

mls qos trust device cisco-phone

mls qos trust cos

auto qos voip cisco-phone

spanning-tree portfast

spanning-tree bpduguard enable

I have configured "trust cos", but I'm skeptical to whether that would work on an access port. Shouldn't I use "trust dscp" instead there?

Also, why in Access mode am I getting COS matches, since the traffic should be untagged:

OIGH-CRS01#sh mls qos int f1/0/9 st

FastEthernet1/0/9

dscp: incoming

-------------------------------

0 - 4 : 288157 0 0 0 0

5 - 9 : 0 0 0 0 0

10 - 14 : 0 0 0 0 0

15 - 19 : 0 0 0 0 0

20 - 24 : 0 0 0 0 8828

25 - 29 : 0 0 0 0 0

30 - 34 : 0 0 0 0 0

35 - 39 : 0 0 0 0 0

40 - 44 : 0 0 0 0 0

45 - 49 : 0 165895 0 0 0

50 - 54 : 0 0 0 0 0

55 - 59 : 0 0 0 0 0

60 - 64 : 0 0 0 0

dscp: outgoing

-------------------------------

0 - 4 : 487606 0 0 0 0

5 - 9 : 0 0 0 0 0

10 - 14 : 0 0 0 0 0

15 - 19 : 0 0 0 0 0

20 - 24 : 0 0 0 0 0

25 - 29 : 0 0 0 0 0

30 - 34 : 0 0 0 0 0

35 - 39 : 0 0 0 0 0

40 - 44 : 0 0 0 0 0

45 - 49 : 0 2437 0 40090 0

50 - 54 : 0 0 0 0 0

55 - 59 : 0 0 0 0 0

60 - 64 : 0 0 0 0

cos: incoming

-------------------------------

0 - 4 : 289904 0 0 8828 0

5 - 7 : 165895 0 0

cos: outgoing

-------------------------------

0 - 4 : 684606 0 0 0 0

5 - 7 : 2437 0 40252

Policer: Inprofile: 0 OutofProfile: 0

paolo bevilacqua · ‎08-15-2007

Hi, I'm not sure about the qos settings as I personally never found them to be necessary, however consider that voice traffic from phone is tagged vlan 5 and can carry COS bits.

royalblues · ‎08-15-2007

It could be because when you use the switchport voice vlan command, the switch negotiates a specialised dot1q trunk which can carry only 2 vlans (data and voice)

Narayan

Aaron Dhiman · ‎08-16-2007

Even when mode is "access"? If there is a dot1q trunk how does that differ from being a trunk port?

Here is the port status:

OIGH-CRS01#sh interfaces f1/0/9 switchport

Name: Fa1/0/9

Switchport: Enabled

Administrative Mode: static access

Operational Mode: static access

Administrative Trunking Encapsulation: negotiate

Operational Trunking Encapsulation: native

Negotiation of Trunking: Off

Access Mode VLAN: 2 (VLAN0002)

Trunking Native Mode VLAN: 1 (default)

Administrative Native VLAN tagging: enabled

Voice VLAN: 5 (VLAN0005)

Administrative private-vlan host-association: none

Administrative private-vlan mapping: none

Administrative private-vlan trunk native VLAN: none

Administrative private-vlan trunk Native VLAN tagging: enabled

Administrative private-vlan trunk encapsulation: dot1q

Administrative private-vlan trunk normal VLANs: none

Administrative private-vlan trunk private VLANs: none

Operational private-vlan: none

Trunking VLANs Enabled: ALL

Pruning VLANs Enabled: 2-1001

Capture Mode Disabled

Capture VLANs Allowed: ALL

Protected: false

Unknown unicast blocked: disabled

Unknown multicast blocked: disabled

Appliance trust: none

paolo bevilacqua · ‎08-16-2007

Well as Narayan said, think about it as 'specialized trunk', where only untagged access vlan, and tagged voice vlan are allowed.

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