CCNP Switch - Multilayer Switching

Node ManNode Man Member Posts: 668 ■■■□□□□□□□
Hi Everyone,
Quick question - A port on a switch set to 'no switch' or Layer 3 mode - Does it automatically perform trunking?

Thanks!

Comments

  • elderkaielderkai Member Posts: 279
    When you make it a routed port, there's no longer a concept of Cisco's trunking since trunking just means a link that passes VLAN tags. It just becomes a layer 3, routed interface.
  • RouteMyPacketRouteMyPacket Member Posts: 1,104
    Node Man wrote: »
    Hi Everyone,
    Quick question - A port on a switch set to 'no switch' or Layer 3 mode - Does it automatically perform trunking?

    Thanks!

    You're a "CCNA"? I question your credentials asking such a question, seriously!
    Modularity and Design Simplicity:

    Think of the 2:00 a.m. test—if you were awakened in the
    middle of the night because of a network problem and had to figure out the
    traffic flows in your network while you were half asleep, could you do it?
  • Node ManNode Man Member Posts: 668 ■■■□□□□□□□
    In retrospect, that was not the brightest question. I should have thought it out first.
  • fredrikjjfredrikjj Member Posts: 879
    You're a "CCNA"? I question your credentials asking such a question, seriously!

    The only thing something like that accomplishes is make people post less, even if their questions are interesting.

    "I'm a CCNP, and I'm interested in this aspect of OSPF, but maybe RouteMyPacket thinks that I should know that already. Nevermind, I'll just google and try to read some blogs."
  • Death DreamDeath Dream Member Posts: 149
    To his defense, the CCNA doesn't cover Layer 3 ports.

    An easy way to remember, Layer 3 ports require the command "no switchport." So any command that required "switchport ......" will no longer work.
  • xnxxnx Member Posts: 464 ■■■□□□□□□□
    Whilst this isn't a part of the CCNA this is something you should really know if you've actually used a Multi Layer Switch before
    Getting There ...

    Lab Equipment: Using Cisco CSRs and 4 Switches currently
  • Dieg0MDieg0M Member Posts: 861
    The above post is not a 100% correct as a switch has no concept of a routed port. What the switch actually does in the background when you enter the "no switchport" command is assign an internal extended VLAN id to that port. This means that one VLAN from the extended range will be used for that port effectively making it a 1 legged L3 VLAN. You can see this port assignment with the command "show vlan internal usage". See below output:

    SW1#sh run int e0/2
    Building configuration...

    Current configuration : 42 bytes
    !
    interface Ethernet0/2
    duplex auto
    end

    SW1#conf t
    Enter configuration commands, one per line. End with CNTL/Z.
    SW1(config)#int e0/2
    SW1(config-if)#no swi
    SW1(config-if)#do sh vlan internal usage

    VLAN Usage
    ----
    1006 Ethernet0/2

    SW1(config-if)#do sh vlan id 1006
    VLAN id 1006 not found in current VLAN database
    SW1(config-if)#exit
    SW1(config)#vtp mode tran
    SW1(config)#vtp mode transparent
    Setting device to VTP Transparent mode for VLANS.
    SW1(config)#vlan 1006
    SW1(config-vlan)#exit
    % Failed to create VLANs 1006
    VLAN(s) not available in Port Manager.
    %Failed to commit extended VLAN(s) changes.

    *Note: This is only valid in IOS, NX-OS handles routed ports on a L3 switch differently.
    Follow my CCDE journey at www.routingnull0.com
  • Node ManNode Man Member Posts: 668 ■■■□□□□□□□
    It's disheartening when people start making accusations but what people should know or not. I've been successfully using 3550s for a long time now.
  • HondabuffHondabuff Member Posts: 667 ■■■□□□□□□□
    Node Man wrote: »
    It's disheartening when people start making accusations but what people should know or not. I've been successfully using 3550s for a long time now.

    Think of the brighter side, You will always know what the "no switchport" command does now!
    “The problem with quotes on the Internet is that you can’t always be sure of their authenticity.” ~Abraham Lincoln
  • OfWolfAndManOfWolfAndMan Member Posts: 923 ■■■■□□□□□□
    Dieg0M wrote: »
    The above post is not a 100% correct as a switch has no concept of a routed port. What the switch actually does in the background when you enter the "no switchport" command is assign an internal extended VLAN id to that port. This means that one VLAN from the extended range will be used for that port effectively making it a 1 legged L3 VLAN. You can see this port assignment with the command "show vlan internal usage". See below output:

    SW1#sh run int e0/2
    Building configuration...

    Current configuration : 42 bytes
    !
    interface Ethernet0/2
    duplex auto
    end

    SW1#conf t
    Enter configuration commands, one per line. End with CNTL/Z.
    SW1(config)#int e0/2
    SW1(config-if)#no swi
    SW1(config-if)#do sh vlan internal usage

    VLAN Usage
    ----
    1006 Ethernet0/2

    SW1(config-if)#do sh vlan id 1006
    VLAN id 1006 not found in current VLAN database
    SW1(config-if)#exit
    SW1(config)#vtp mode tran
    SW1(config)#vtp mode transparent
    Setting device to VTP Transparent mode for VLANS.
    SW1(config)#vlan 1006
    SW1(config-vlan)#exit
    % Failed to create VLANs 1006
    VLAN(s) not available in Port Manager.
    %Failed to commit extended VLAN(s) changes.

    *Note: This is only valid in IOS, NX-OS handles routed ports on a L3 switch differently.

    Wow! I'm totally going to check this out. Good to know! Rep for you sir!
    :study:Reading: Lab Books, Ansible Documentation, Python Cookbook 2018 Goals: More Ansible/Python work for Automation, IPSpace Automation Course [X], Build Jenkins Framework for Network Automation []
  • omi2123omi2123 Member Posts: 189
    It seems like you know it all when it comes to Cisco. Why don't you keep this kind of insulting comments to your self & seek life elswhere ?
    You're a "CCNA"? I question your credentials asking such a question, seriously!
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