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No switchport vs. ip routing

On a L3 switch, does no switchport take the place of ip routing? If I have ip routing disabled, and go to interface g1/0/5 and run no switchport there, and assign an address, will it have the same effect? (route traffic, etc.)

Thanks!

--John

HTH, John *** Please rate all useful posts ***
8 REPLIES

Re: No switchport vs. ip routing

Hi John,

You should enable IP routing.

Without this you won't have your ip routing table.

Cheers:

Istvan

Re: No switchport vs. ip routing

So in what situation would you ever set the port to be a "no switchport?" This command puts the interface in routing mode, but if the ip routing command does this across all ports, then what's the advantage of ever using the no switchport command?

HTH, John *** Please rate all useful posts ***

Re: No switchport vs. ip routing

Hi,

L3 Switches are capable of L2 and L3. The command "Switchport" turns the port to be a L2 capable. The command "no switchport" makes the switchport L3 capable. As far as "ip routing" command is concerned, this enables the routing between the L3 ports on the same switch.

Hope this Helps......

Shaheen

Re: No switchport vs. ip routing

I'm still confused:

"no switchport" makes the port L3 capable, but what purpose would this serve in the situation if ip routing were NOT enabled?

I have a L3 switch that has ip routing enabled, but it just occurred to me that none of my switchports are "no switchport" enabled. All of them are standard.

Does the ip routing allow you to create SVIs on a L3? I've searched on Cisco's site and I can't find anything telling me what the real difference is.

Thanks,

--John

HTH, John *** Please rate all useful posts ***

Re: No switchport vs. ip routing

Hi John,

L3 Switch is already capable to allow you create SVIs, you don't have to turn the ip routing on to do this.

To do the ip routing you don't have to create SVIs. This is just an extra option which helps to make a better use of L3 Switch, you can run various Vlans.

When you turn IP routing on, thats when various SVIs or L3 interfaces start exchanging routing info.

Hope This Helps....

Shaheen

Re: No switchport vs. ip routing

Okay, so given this scenario does this make sense (to see if I understand):

ip routing enables communication between vlans. If this is the case, if it's not enabled and the switch allows you to create SVIs, the do you need to create static routes on the switch to get to other vlans?

no switchport allows you to assign an address that would leave the switch based off of the routing table?

g3/0/2

no switchport

ip address public address

This interface would connect to a router and the switch would know how to direct traffic out of the switch?

Thanks for you responses Shaheen

--John

HTH, John *** Please rate all useful posts ***

Re: No switchport vs. ip routing

Hi John,

Yes,

Thats correct.

HTH

Shaheen

Hall of Fame Super Blue

Re: No switchport vs. ip routing

John

Just to clarify.

"ip routing enables communication between vlans" - yes but it doesn't necessarily have to be between vlans ie. you could route between a vlan and a routed port on the switch.

"if it's not enabled and the switch allows you to create SVIs, the do you need to create static routes on the switch to get to other vlans? "

ip routing does not just enable dynamic routing - it enables all routing. So you can create multiple vlan interfaces but without enabling "ip routing" you won't be able to inter-vlan route on the switch regardless of statics. You wouldn't need statics anyway as all the SVI's would be directly connected.

If you mean to get to other vlans that have L3 SVI's on other switches then yes statics would do it but you still need to enable "ip routing" on both switches.

There are as other posters have said 2 types of L3 interface on a L3 switch

1) L3 SVI - vlan interface

2) in an interface - "no switchport" and then an ip address.

"g3/0/2

no switchport

ip address public address

This interface would connect to a router and the switch would know how to direct traffic out of the switch?"

Doesn't have to a router - could be another L3 switch. The point is it is not a L2 link - it is a L3 routed link.

Jon

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