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Weekly Open Ended Question #5
This is the fifth question in a series of OEQs. The answer to the fourth question has been added to the post.
Fifth question:
What protocol is used to automatically form trunks on a Cisco switch and how do you disable it?
about 1 month ago
DTP forms trunks automatically – Switchport nonegotiate turns it off I believe.
about 1 month ago
VTP
can’t disable it, closest you can come is transparent mode
Port Modes
desirable makes it so it tries to become a trunk
active makes it accept becoming a trunk if the other one tries to be a trunk
access, makes it so it it is just an access port
truk, makes it so it is a trunk port
and not a big fan of the “make sure this person is human” thing, unless you have had an issue with it in the past
about 1 month ago
VTP has nothing to do with forming trunks Daniel.
about 1 month ago
I had to add the CAPTCHA stuff cause I was getting a ton of spam. I figured no one would like it, but it’s a lot easier than manually removing all the spam posts every day.:)
One nice thing is that if you register on here you won’t have to do it.
about 1 month ago
DTP
switchport mode nonnegotiate creates a perminent trunk with no dtp
or
switch port mode access creates permanent non-trunk and also does not run DTP
about 1 month ago
If the VTP domain is different on the switches, the trunk will not come up automatically.
Am I right?
Note: Some of the switches do not show this error message.
4w2d: %DTP-SP-5-DOMAINMISMATCH: Unable to perform trunk negotiation on port Fa3/
3 because of VTP domain mismatch.
The solution for this issue is to manually force the trunking instead in order to rely on the DTP. Configure the trunk ports between the switches with the switchport mode trunk command.
Switch1(config)#interface fastethernet 1/0/23
switch1(config-if)#switchport mode trunk
Switch2(config)#interface fastethernet 3/3
switch2(config-if)#switchport mode trunk
http://www.cisco.com/en/US/tech/tk389/tk689/technologies_tech_note09186a0080890613.shtml
about 1 month ago
@ZeroZeroFourteen
Depending on how you interpret this question I would say your response it not totally correct. While “switchport nonnegotiate” does disable DTP on the port which prevents automatically forming a trunk “switchport mode trunk” does not disable DTP and will automatically for a trunk with the other side if that side is set to on/auto/desirable.