03-03-2010 07:50 AM - edited 03-15-2019 09:37 PM
I am just getting into VoIP and have a question about trunking with switches. The network I am working on has some different configurations for trunking on different switches. And I don't see why.
Example:
Switch_01
interface GigabitEthernet0/1
switchport trunk encapsulation dot1q
switchport mode trunk
srr-queue bandwidth share 10 10 60 20
srr-queue bandwidth shape 10 0 0 0
queue-set 2
mls qos trust cos
auto qos voip trust
Switch_02:
interface GigabitEthernet0/1
switchport trunk encapsulation dot1q
switchport mode trunk
Access Ports
interface FastEthernet0/1
switchport access vlan 10
switchport trunk encapsulation dot1q
switchport mode dynamic desirable
switchport voice vlan 172
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
Currently changing switchport mode dynamic desirable to sw mode access, due the 7970 series phones dropping out.
They are both connected the the 6509 and I do not see any reason for the difference. I would like to eventually like to put them on a different Native VLAN.
Do I need the srr-queue, cos and auto qos lines?
What is cos and dscp, and what are the benifits?
Solved! Go to Solution.
03-03-2010 08:01 AM
Hi
So many questions!
The first config and second config examples are the same, except the first also has QoS configured on it. These configurations are suitable for links between switches, all VLANs will be carried accross as they are configured as trunks.
The third config is an edge port config, but not a great one as you've discovered. In the middle ages it was normal to configure the edge ports as dot1q trunks to allow the phones to get into a different VLAN to the PC that was attached to the phone, but that's not what you would do now. A more suitable port config would be:
int x/x
switchport mode access
switchport access vlan X <--- whatever VLAN you want for the PC
switchport voice vlan Y <.--- VLAN for the phone
auto qos voip cisco-phone <--- see below
spanning-tree portfast < start the port quickly rather than going through full STP process
In terms of QoS, DSCP, etc... there's lots to know here. If you're new to QoS, set 'auto qos voip cisco-phone' on your edge ports, and 'auto qos voip trust' on all inter-switch links, and then read up on it! There's lots of info on the Cisco web site...
Essentially once you do this you will have a network that runs on CoS markings. CoS is a field in the dot1q or ISL header found on trunk or Voice VLAN enabled interfaces.
DSCP is a field in the IP Header that is more granular, and has the advantage of being present on all IP packets whether traversing a trunk link or not.
There are maps on the switch that will rewrite each of these fields based on configured settings - these settings are applied to the switch the first time that you enter an 'auto qos' command on a port, so you don't have to get too hung up on it for now.
Regards
Aaron
Please rate helpful posts...
03-03-2010 08:01 AM
Hi
So many questions!
The first config and second config examples are the same, except the first also has QoS configured on it. These configurations are suitable for links between switches, all VLANs will be carried accross as they are configured as trunks.
The third config is an edge port config, but not a great one as you've discovered. In the middle ages it was normal to configure the edge ports as dot1q trunks to allow the phones to get into a different VLAN to the PC that was attached to the phone, but that's not what you would do now. A more suitable port config would be:
int x/x
switchport mode access
switchport access vlan X <--- whatever VLAN you want for the PC
switchport voice vlan Y <.--- VLAN for the phone
auto qos voip cisco-phone <--- see below
spanning-tree portfast < start the port quickly rather than going through full STP process
In terms of QoS, DSCP, etc... there's lots to know here. If you're new to QoS, set 'auto qos voip cisco-phone' on your edge ports, and 'auto qos voip trust' on all inter-switch links, and then read up on it! There's lots of info on the Cisco web site...
Essentially once you do this you will have a network that runs on CoS markings. CoS is a field in the dot1q or ISL header found on trunk or Voice VLAN enabled interfaces.
DSCP is a field in the IP Header that is more granular, and has the advantage of being present on all IP packets whether traversing a trunk link or not.
There are maps on the switch that will rewrite each of these fields based on configured settings - these settings are applied to the switch the first time that you enter an 'auto qos' command on a port, so you don't have to get too hung up on it for now.
Regards
Aaron
Please rate helpful posts...
03-04-2010 11:21 AM
Thank you for the info.
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