hi every body!
i have some questions about DTP.
According to cisco, DTP covers
encapsulation negotiation( isl or dot1q)and whether the link becomes a trunk at all.
Let say we have two swithes:
sw1 and sw2
sw1 is connected to sw2 by f0/1 and sw2 is connected to sw1 by f0/1.
Both are trunking.
sw1(config) interface f0/1
sw1(config-if)switchport trunk encapsulation negotiate.
sw1(config-if)switchport mode trunk.
Assume sw2 has the similar configuration in place. I turn off the DTP on both switches. With DTP turned off on both swithes, how the encapsulation would be negotiated i.e isl or dot1q between sw1 and sw2?
simply put, when dot1q or isl need to be
negotiated between two switches should they have "DTP" turned on?
I have one more question about trunk link.
Can i use any port from any vlan for trunking? for example if i have switch with vlan 2 and vlan 3 , can i use the port from vlan3 for trunking or the port should be from native vlan?
There is something not quite right about ur pasted config lines. this is what happens when I try it.
TST-POP1-NPE01(config-if)#switchport trunk encapsulation negotiate
TST-POP1-NPE01(config-if)#switchport mode trunk
Command rejected: An interface whose trunk encapsulation is "Auto" can not be configured to "trunk" mode.
Command rejected: Conflict between 'nonegotiate' and 'dynamic' status.
In order to turn off DTP, u need to set encapsulation and mode manually. which means, you won't be in a situation where DTP is off and encapsulation not set.
when DTP is on and encapsulation not specified, link will default to Cisco proprietary ISL.
With regards to trunking VLANs, u can trunk VLAN2 and VLAN3 on same port. I hope I understood ur question correctly.
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