?
Solved

Switch Trunk

Posted on 2014-11-16
11
Medium Priority
?
313 Views
Last Modified: 2014-11-22
If I understand a Trunk link can be formed between 2 Switches if the ports are:

Trunk-Trunk
Trunk-Auto,Desirable
Auto,Desirable-Auto-Desirable

However sometimes , in addition to configuring the port as Trunk, I have seen the command Nonegotiate added.

ports cannot also form a Trunk when they are in 2 different Domains.

I wonder if there is a list that covers all the situations and combinations when 2 switch ports can form a Trunk and when they cannot ?

Thanks
0
Comment
Question by:jskfan
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 5
  • 3
  • 2
11 Comments
 
LVL 50

Expert Comment

by:Don Johnston
ID: 40446485
Not sure if I'm interpreting your post correctly, but auto-auto will not result in a trunk.
0
 

Author Comment

by:jskfan
ID: 40447470
Don,
I know Auto - Auto does not form Trunk
Sometimes they use Switchport Nonegotiate, I wonder what impact does it have in forming a Trunk
Switchport Nonegotiate can be used in conjunction with Switchport mode Access and Switchport mode Trunk.
0
 
LVL 30

Assisted Solution

by:Predrag
Predrag earned 1000 total points
ID: 40447548
Switchport nonegotiate disables DTP (dynamic trunk negotiation), so you can still form trunk if on other switch ports is set to trunk (with or without nonegotiate), but port won't do negotiation on that port.
I dont see any point using it with switchport mode access.
And also, if you put switchport nonegotiate you can form working trunk between different VTP domains, since trunk is hard coded.
0
VIDEO: THE CONCERTO CLOUD FOR HEALTHCARE

Modern healthcare requires a modern cloud. View this brief video to understand how the Concerto Cloud for Healthcare can help your organization.

 

Author Comment

by:jskfan
ID: 40447718
I do not understand the usage of trunk nonegotiate other than disabling DTP. what 's the impact of disabling DTP ?

So Trunk will still form regardless if nonegotiate is typed or not as long as you type:
Switch mode Trunk
Which means the Trunk is ON
0
 
LVL 30

Assisted Solution

by:Predrag
Predrag earned 1000 total points
ID: 40447771
switchport mode trunk still send DTP frames although it is in trunk mode.
switchport nonegotiate prevents port from sending DTP frames.

First case (without nonegotiate)
switchport mode trunk will be still able negotiate trunk with other side if other side is configured as auto or dynamic desirable.
Second case (with nonegotiate)
If switchport nonegotiate is issued on port configured with switchport mode trunk command and other side is configured as auto or dynamic desirable, one side will be trunk and other side will be access port.
0
 

Author Comment

by:jskfan
ID: 40458896
If switchport nonegotiate is issued on port configured with switchport mode trunk command and other side is configured as auto or dynamic desirable, one side will be trunk and other side will be access port.

Which means the Trunk will not form ?
0
 
LVL 50

Assisted Solution

by:Don Johnston
Don Johnston earned 1000 total points
ID: 40458922
That is correct. There will not be a trunk between the two switches.  However, that does not mean that traffic can't flow.

One side will treat the link as a trunk and tag all VLANs except the native VLAN.  The other side will treat the link as an access link and send/receive frames for the configured VLAN.

Which means that the native VLAN on the trunking side will be able to communicate with the access VLAN on the other.
0
 

Author Comment

by:jskfan
ID: 40459457
SO that 's what I concluded, if I am not wrong :
The Trunk will form if both sides are :
-Trunk-Trunk, Trunk-Auto, Desirable-Auto, Desirable-Desirable. Trunk-Desirable.
-if both side are Auto-Auto, the trunk will not form.
-If one port on one side is configured  with Switchport mode Trunk/NoNegotiate command and the other side with Switchport mode Trunk, This will form a Trunk.
- If one port on one side is configured  with Switchport mode Trunk/NoNegotiate command and the other side with Switchport mode Trunk/Nonegotiate, This will
form a Trunk.
-If one port on one side is configured  with Switchport mode Trunk/NoNegotiate command and the other side with Dynamic Desirable, This will Not form a Trunk.
0
 
LVL 50

Accepted Solution

by:
Don Johnston earned 1000 total points
ID: 40459459
You are correct on all counts.
0
 

Author Closing Comment

by:jskfan
ID: 40459523
Thank you Guys!
0

Featured Post

Get real performance insights from real users

Key features:
- Total Pages Views and Load times
- Top Pages Viewed and Load Times
- Real Time Site Page Build Performance
- Users’ Browser and Platform Performance
- Geographic User Breakdown
- And more

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

There are two basic ways to configure a static route for Cisco IOS devices. I've written this article to highlight a case study comparing the configuration of a static route using the next-hop IP and the configuration of a static route using an outg…
This article will show how Aten was able to supply easy management and control for Artear's video walls and wide range display configurations of their newsroom.
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…
Suggested Courses

770 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question