Wired Intelligent Edge

Hi guys,

Please your help for a couple of doubts about QoS on Aruba switches:

1. Is there any feature on Aruba like the Auto-Qos on Cisco switches? I don't see something similar when browsing throughout the CLI.

2. If there is a Cisco IP phone connected to the switch port, is it better to trust CoS (dot1p) or DSCP?

SWLIMA(eth-3)# qos trust
default     Trust 802.1p priority and preserve DSCP or IP-ToS.
device     Trust DSCP when the port is connected to a specified
device type.
dot1p      Trust 802.1p priority and preserve DSCP or IP-ToS.
dscp        Trust DSCP and remark the 802.1p priority to match.
ip-prec     Trust IP-Precedence and remark the 802.1p priority to
match.
none       Do not trust any priority fields, and remark all of them
to 0.

For the last, I guess if I trust CoS or dot1p, it doesn't make sense to apply the global command "qos type-of-service diff-services" since prioritize IP packets based on their DSCP instead of CoS.

SWLIMA(config)# qos type-of-service
diff-services       Prioritize IP packets based on their DSCP codepoint.
ip-precedence    Prioritize IPv4 packets based on their ToS precedence.

Please your help.

Regards,

Julián

Julian,

I prefer always to use DSCP instead of dot1p. Cisco phones marks the DSCP traffic by default with DSCP mark 46.

To use this value.

qos type-of-service diff-services

interface x
   qos trust dscp

The default is to use the dot1p value and preserve the DSCP value.

DSCP 46 will be placed by default in the highest queue, queue 8. (at least with the 2930f and higher models).

Hi Willem,

Thank you for your interest on this. Please help me with this:

I prefer always to use DSCP instead of dot1p. Cisco phones marks the DSCP traffic by default with DSCP mark 46.

The default is to use the dot1p value and preserve the DSCP value.

What happens if I use the default and trust dot1p? Cisco IP phones only marks the DSCP field in the IP packet but they don't mark the 802.1p field in the frame? If that is the case, it makes sense to trust DSCP. But if they mark also the 802.1p field, I could also use the dot1p, right?

There is another command:

vlan x

  voice

  tagged 1-10

Isn't that enough to prioritize the voice traffic that is received inbound on the port? Should I use the two commands all together to prioritize the voice traffic (qos trust dscp and voice)?

Regards,

Julián

What happens if I use the default and trust dot1p? Cisco IP phones only marks the DSCP field in the IP packet but they don't mark the 802.1p field in the frame? If that is the case, it makes sense to trust DSCP. But if they mark also the 802.1p field, I could also use the dot1p, right?

The Cisco Phones also mark the traffic with 802.1p. However, this only works when the traffic is tagged and not untagged because the 802.1p value in the the VLAN header.

There is another command:

vlan x

  voice

  tagged 1-10

This only enabled the switch to transmit LLDP-MED to tell the phone to use VLAN x as the voice VLAN.

Isn't that enough to prioritize the voice traffic that is received inbound on the port? Should I use the two commands all together to prioritize the voice traffic (qos trust dscp and voice)?

The voice command is to send LLDP-MED in the LLDP data. This has nothing to do with QoS. The default of the switch is to use 802.1p. So, if the only requirerement is to prioritize the VOICE traffic of the Cisco phones than the default are ok. In this case make sure that the voice traffic is send tagged.

I prefer to use DSCP because 802.1p is in the VLAN header. This gives the possibility to use the DSCP field of a client is sending untagged data.

Hi Willem,

Much clear, thank you. One more thing. If I use the default to use dot1p to prioritize the voice traffic, which is fine for me because the voice traffic will be tagged, do I have to use the command "qos type-of-service diff-services" as well?

SWLIMA(config)# qos type-of-service
diff-services       Prioritize IP packets based on their DSCP codepoint.
ip-precedence    Prioritize IPv4 packets based on their ToS precedence.

Because if I use the default, dot1p field will be used to prioritize the voice traffic, but with that command, DSCP will be used to prioritize the voice traffic as the command output shows. So it seems both commands can't work together, or one of them will override the other one. Do you know this?

Regards,

Julián

In your case it's not needed to configure the qos type-of-service command. 

Hi Willem,

One more thing please. In case I trust DSCP, do I need to apply the command "qos trust dscp" on the interface? Because by applying the command "qos type-of-service diff-services" the traffic is already prioritized based on the DSCP code:

SWLIMA(config)# qos type-of-service
diff-services Prioritize IP packets based on their DSCP codepoint.
ip-precedence Prioritize IPv4 packets based on their ToS precedence.

It seems applying both commands will be redundant. Am I right? Or missing something?

On the other hand, is there any command for the switch to say the phone to tag its traffic in a specific VLAN? I think this is accomplish in Cisco with the command "switchport voice vlan vlan-id".

Regards,

Julián

One more thing please. In case I trust DSCP, do I need to apply the command "qos trust dscp" on the interface? Because by applying the command "qos type-of-service diff-services" the traffic is already prioritized based on the DSCP code:

 

SWLIMA(config)# qos type-of-service
diff-services Prioritize IP packets based on their DSCP codepoint.
ip-precedence Prioritize IPv4 packets based on their ToS precedence.

 

It seems applying both commands will be redundant. Am I right? Or missing something?

I'm not sure if both commands are needed. The documentation is not very clear about this. I should say use both.

On the other hand, is there any command for the switch to say the phone to tag its traffic in a specific VLAN? I think this is accomplish in Cisco with the command "switchport voice vlan vlan-id".

---

You can set this within the VLAN. For example

vlan 10
 qos priority 6

But in that case all the traffic in that VLAN is set queue 7. I don't prefer this approche. 

Hi,

OK, I am clear for the first part. For the second,

On the other hand, is there any command for the switch to say the phone to tag its traffic in a specific VLAN? I think this is accomplish in Cisco with the command "switchport voice vlan vlan-id".

---

You can set this within the VLAN. For example

 

vlan 10
 qos priority 6

But in that case all the traffic in that VLAN is set queue 7. I don't prefer this approche. 

---

There is a misunderstanding. I don't mean to set a priority for the voice VLAN, I mean a command for the switch to tell the phone to tag its traffic with a certain VLAN tag. For example, in Cisco, with the command "switchport voice vlan 20", the switch tells the phone to tag all its traffic within VLAN 20. Is there a similar command on Aruba switches?

Regards,

Julián

There is a misunderstanding. I don't mean to set a priority for the voice VLAN, I mean a command for the switch to tell the phone to tag its traffic with a certain VLAN tag. For example, in Cisco, with the command "switchport voice vlan 20", the switch tells the phone to tag all its traffic within VLAN 20. Is there a similar command on Aruba switches?

When you set the VOICE command in the VLAN context the Aruba switch tells the phone to use VLAN 20. This is done using LLDP-MED but the phone needs to support this. If the Cisco phone doesn't support this you have to set the following command

cdp mode pre-standard-voice

Really old Cisco phones only support CDP and not LLDP. First test with LLDP.

Hi,

Great, much clearer. Yeah, my customer has both new and old Cisco phones. In fact, I had to use command "power-over-ethernet pre-std-detect" to power the old Cisco phones.

Thanks very much for your help!

Julián

Details here: https://community.arubanetworks.com/t5/Wired-Intelligent-Edge-Campus/AOS-Switch-and-Cisco-IP-Phones-PoC-Testing-CDP-Voice-VLAN-QoS/td-p/538189

Hi Adolfo,

Just awesome, very good contribution!

Regards,
Julián