02-19-2013 06:25 PM - edited 03-04-2019 07:04 PM
Hi,
I wonder if we still need to configure 'mls qos trust dscp' at switch access port. the switch is kind of layer 2 function. it currently not enabled 'mls qos' by global command.
I would like to trust dscp value when the packet is passing above L2 switch access port. but it's not configured 'mls qos' and 'mls qus trust dscp'.
02-19-2013 09:12 PM
you can also think this way..
Let's say there is an ip phone connected to L2 switch access port..you need to trust the COS value within L2 domain and DSCP or IP precedence value on L3 domain..generally LAN segment will be of larger bandwidth (gig links) and may not suffer congestion..so even if you do not trust COS, it may not lead to trouble over the trunks..however it is best practise to trust COS on L2 domain..
So trusting dscp on access port will ensure the precedence or dscp will be preserved until it reach the destinaton and will be used by layer 3 hops..but it needs to trusted end to end...
there are many experts here, and i may seek some corrections
02-19-2013 09:19 PM
Hi, I got your point.
actually, TP device will connect to access port. the diagram is like below.
TP device --- Layer 2(mls qos trust dscp) --- Layer 3( mls qos trust dscp) -- Layer 2(not mls qos trust dscp) --- Router --- WAN
we set and classified TP traffic accodingly on first layer 2 switch. and it's configured 'mls qos trust dscp) till 2nd switch.
I wonder if 2nd layer 2 switch is still need 'mls qos trust dscp' this is switch what I quired as above.
the configuration likes below.
interface GigabitEthernet1/0/13
switchport access vlan 60
switchport mode access
speed 1000
duplex full
no mdix auto
end
02-19-2013 09:36 PM
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