CCNP Switch - Multilayer Switching

Hi Everyone,
Quick question - A port on a switch set to 'no switch' or Layer 3 mode - Does it automatically perform trunking?

Thanks!

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elderkai

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.

RouteMyPacket

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!

Node Man

In retrospect, that was not the brightest question. I should have thought it out first.

fredrikjj

RouteMyPacket wrote: »

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 Dream

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.

xnx

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

Dieg0M

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.

Node Man

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.

Hondabuff

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!

OfWolfAndMan

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!

omi2123

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 ?

RouteMyPacket wrote: »

You're a "CCNA"? I question your credentials asking such a question, seriously!