cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
2086
Views
0
Helpful
10
Replies

Prioritize traffic for VLANs on 3750X

sebastien3
Level 4
Level 4

Hello,

 

I use 3750X switches with IOS version 152-4.E9.

I'm looking to prioritize all traffic for VLANs 10 to 30 (data enterprise), the other VLANs will be in best effort.

 

Is it possible to prioritize traffic for some VLAN ?

 

Thank you in advance for your help.

10 Replies 10

balaji.bandi
Hall of Fame
Hall of Fame

Instead of VLAN, you can do per Subnet IP based QoS Policy.

 

reference  guide :

 

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750/software/release/12-2_35_se/configuration/guide/scg/swqos.html?referring_site=bodynav

BB

***** Rate All Helpful Responses *****

How to Ask The Cisco Community for Help

Joseph W. Doherty
Hall of Fame
Hall of Fame
Yes you can. (How varies much depending on your requirements and network topology. Generally, not too difficult, but can be tedious.)

Is it possible to have a policy-map with VLANs?


Should we do QoS on traffic only or should we specify a bandwidth?

VLAN 10 which will have priority over traffic for example from VLAN 8. The two VLANs are connected to 100M.

Which method to use?

Below are restrictions applied when you do QOS based on VLAN Tags.:

"The router does not support the random-detect and priority commands for traffic classes created using the match-vlan command in class maps"

Ref: https://www.cisco.com/c/en/us/td/docs/ios/12_2sb/feature/guide/vlntgqos.html

 

The best option for you would be matching subnet which will support "Priority" configuration for the traffic classified by class_maps.

I recommend to use an access-list with subnet associated with VLAN and create QoS Policy based on that to mark as per the requirement.

 

 

BB

***** Rate All Helpful Responses *****

How to Ask The Cisco Community for Help

OK I will use an access-list with subnet, I will not use VLANs !

If I understand it is necessary to make two configurations, one on the switch and the other on the router ?

It is not possible to do QoS only on the switch in order to prioritize subnet ?

Usually there is no need to apply it on the LAN witches due to high speed links available already.

 

We need to apply QOS on slower links which are WAN links in most of the cases that are terminating on the Routers.

 

So, apply it on the Edge Router which is terminating WAN connections.

"Should we do QoS on traffic only or should we specify a bandwidth?"

Sorry, I don't understand the question.

As noted in my earlier reply, yes you can prioritize one VLAN's traffic over another on a 3750-X. How, though, depends on your topology.

"Which method to use?"

Again, your question, to me, is unclear. Which methods did you want to have an opinion on?

 

[edit - PS:}

 

BTW, the configuration guide for a 3750-X, 15.2(4)E is: https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750x_3560x/software/release/15-2_4_e/configurationguide/b_1524e_consolidated_3750x_3560x_cg/b_1524e_consolidated_3750x_3560x_cg_chapter_0101110.html

 

This is a bit more germane to your question on 3750-X QoS then the other posters' references.

 

You might want to start with the section on "Restrictions for QoS".

Here is the network diagram : network.jpg

For example on switch 5 the uplink is only 100M, I want to prioritize VLANs 10 and 20 (subnet 192.168.10.X & 192.168.20.X) if for example VLANs 7 and 8 are too consuming.

 

The speed must always have priority for SUBNET 192.168.10.X to 192.168.30.X, the others will not have priority ...

 

Do you understand what I am trying to do?

"Do you understand what I am trying to do?"

Somewhat.

How to you understand priority? What does it mean to you? For example, on the 3750 you can have one traffic set have absolute priority over all other traffic (normally used for VoIP) or you can set relative bandwidth percentages. An example of the latter, one set of traffic might be guaranteed to obtain 3x the bandwidth of another set of traffic. (NB: these guarantees are minimums.)

The 3750 has 4 egress queues (when QoS is enabled), per port.

Regardless, in principle, all the "priority" VLAN edge ports should have a policy that "tags" the ingress traffic with some specific ToS marking. All other ports that might have "new" ingress "return" traffic should also "tag" packets going to your priority VLANs.

Transit ports (e.g. uplink and downlink) should have QoS configured to provide the desired "priority" to the "priority" marked packets.

On the 3750 series, QoS first has to be enabled. (NB: doing so, sets a default set of QoS parameters that often increase interface drops!) On these devices, you can have two QoS global port configurations you can configure, one of which (first one, by default) is applied to all ports. Often the first configuration set is used for access/edge ports and the second configuration set used for transit ports. (NB: the 3750 has more physical buffer resources for it's "uplink" ports!)
Getting Started

Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community: