Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

3750 Access Port Question

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

4 REPLIES
Hall of Fame Super Gold

Re: 3750 Access Port Question

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.

Re: 3750 Access Port Question

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

New Member

Re: 3750 Access Port Question

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

Hall of Fame Super Gold

Re: 3750 Access Port Question

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

As a recognition to those providing answers, please rate useful posts!/

112
Views
6
Helpful
4
Replies