Spanning Tree Network Ports vs Normal Ports

Spanning Tree Network Ports vs Normal Ports

In Cisco link :https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus5000/sw/configuration/guide/cli/CLIConfigurationGuide/SpanningEnhanced.html
it talks about Network Ports and Normal Ports.
To me both sounds like Trunk Ports.

Any clarifications on that ?

Thank you
jskfanAsked:
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atlas_shudderedSr. Network EngineerCommented:
You are looking at cisco specific documentation of extensions to STP for the Nexus line of switches.  Specifically STP extensions for port type.  These extensions allow a Nexus switch to self enable particular interface functionality and influence impact to STP and convergence.  There are three types of ports; normal, network and edge.

Normal ports are handled as normal network ports and can be connected to bridges, switches or end hosts.

Network ports are assumed connected to other switches or bridges and will auto enable bridge assurance on the Nexus platform.  The port will available to participate in STP.

Edge ports are assumed connected to end hosts only (whether server, workstation, NAS, etc.) and will not participate in STP.

Nexus STP Port Types do not have any affect on whether a port is a trunk or not.
Don JohnstonInstructorCommented:
Can you be more specific as to what you're looking for.

With respect to "normal", the document states there are Network, Edge and Normal ports.

Edge ports should only be connected hosts or end stations.  Network ports are only to be connected to switches or spanning-tree aware devices. Normal ports could be connected to either.
jskfanAuthor Commented:
OK , what I understand:

The Edge Port is similar to Access Port
Network Port is similar to  Trunk Port

Normal Port , is not clear... does it detect the other side so as to form Trunk or Access ?
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Don JohnstonInstructorCommented:
No.

Trunk and access ports have nothing to do with spanning tree.

For example, a trunk port can be an edge port or a network port.

So forget trunk and access when discussing spanning tree port types.

An edge port is connected to an end station.  A device that would never forward traffic (a PC, server, printer).   A network port is connected to a spanning tree aware device (bridge or switch).  These port types are defined in the configuration.

A normal port could be connected to either an end station or a switch.
atlas_shudderedSr. Network EngineerCommented:
jsk -

As noted in my original message:

Nexus STP Port Types do not have any affect on whether a port is a trunk or not.
jskfanAuthor Commented:
so how do you make a port as Normal port ?
Don JohnstonInstructorCommented:
Do nothing. That's the default.
atlas_shudderedSr. Network EngineerCommented:
If no changes are made to the port or the global defaults then normal is the default port type in Nexus.  Cisco best practice is to set the global default to edge though.  Insures that if an STP capable device is connected to the switch without admin intervention, the port is disabled automatically.
jskfanAuthor Commented:
So
Normal port can be connected to  Hosts or to Switches.   so Normal port does not understand STP ?

Network Port , understands STP.    how do you make a port as  Network port ?

Edge port , I believe it does not understand STP  , if you connect it to a Switch, what would happen ?

Thanks
atlas_shudderedSr. Network EngineerCommented:
All the port types understand STP.  What is at issue is how the ports handle STP, BPDU's, etc.  Specific to this question:

Normal - Handles BPDU's as normal STP.
Edge - assumed non-spanning tree connection, any bpdu seen on the port leads to port err-disable
Network - assumed to STP capable device, handles STP in fast bridging

To configure
by port

config t
interface ethernet x/n/x
spanning tree port type edge|normal|network

Open in new window


or globally

config t
spanning tree port type edge|normal|network default

Open in new window

Don JohnstonInstructorCommented:
Normal port can be connected to  Hosts or to Switches.   so Normal port does not understand STP ?
No.  Normal ports understand STP.  Actually, all ports understand STP.

Network Port , understands STP.    how do you make a port as  Network port ?
spanning-tree port type network

Edge port , I believe it does not understand STP  , if you connect it to a Switch, what would happen ?
No.  It depends on the configuration, but if an edge port is connected to a switch, the port go into error-disable mode.
atlas_shudderedSr. Network EngineerCommented:
So.   Ive got to ask.  Would it be better if I just ceased answering or would that hinder the ability to repeat my answers?
jskfanAuthor Commented:
Sorry for keeping asking. I need to be clear on the subject

<<Edge - assumed non-spanning tree connection, any bpdu seen on the port leads to port err-disable>>

This sounds like an access port with BPDU Guard enabled.


Network Port:<<network port is connected to a spanning tree aware device (bridge or switch).>>

This sounds like a trunk port


Normal Port : If it understands STP then it can act as Network Port when connected to a Switch.
it sounds like it should not be put for Client computers to connect to, otherwise if someone remove a PC and puts a switch it can create a TCN
atlas_shudderedSr. Network EngineerCommented:
jsk -

Comment wasn't directed at you.  No worries.

Your comment about the edge port is reasonable however, there is more going on below the covers there than just bpdu guard, there is also portfast, etc.

Regarding the network port.  I understand how you are getting to that conclusion however, you have to remember that you can have two l2 devices connected and not run the link as a trunk.  Not that this matters much.  The point being that a network point assumes that it is going to be connected to another layer 2 device and treats it as such.  This automatic treatment centers around STP, not trunking.

The easiest way to look at a normal port is to think about it as behaving like a port on a 3850, 2960 etc.  The port is STP aware, with no other intelligence included other than what you directly configure it with.

The big thing with port types is to look at it from a STP perspective.  The nexus platforms allow you to exercise more flexible managment and administration of the equipment both globally, functionally, feature wise and port by port than the catalyst line.  Port types is one of these areas.  By using port types, you can exercise more granular control of STP itself globally and port by port.  This has the net effect of a more stable STP topology and network overall.

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jskfanAuthor Commented:
Thank you
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