From: MADMAN (dave@interprise.com)
Date: Fri Nov 15 2002 - 16:24:35 GMT-3
Joe A wrote:
>
> Guys,
>
> When running IOS on the Catalyst 6500, what is the difference between
> the following:
>
> First, put a bunch of interfaces (ports) into VLAN 20, including port
> 3/1, then configuring:
>
> interface FastEthernet 3/1
> ip address 10.1.1.1 255.255.255.0
You can't do that, if you assigned 3/1 to VLAN 20 it is a layer 2
port.
> OR
>
> First, put a bunch of interfaces (ports) into VLAN 20 and then assign
> the IP address
> to a logical VLAN interface itself:
>
> interface VLAN 20
> ip address 10.1.1.1 255.255.255.0
>
> Do these accomplish the same thing?
By default the ports in Native mode are L3. If you make them L2 you
allow all the devices on the same VLAN to communcate at L2 and you tie
those ports to an L3 interfave via the interface VLAN x so they can get
"off net" so they are not the same.
>
> Another question, what makes an interface a 'layer 3' interface, just
> the presence of a layer 3 address, or is there more to it?
The presence of the IOS command "switchport" or lack thereof is the
differance.
Native6506#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Native6506(config)#inter fa
% Incomplete command.
Native6506(config)#inter fa3/1
Native6506(config-if)#swit
Native6506(config-if)#switchport ac
Native6506(config-if)#switchport access vlan 20
Command rejected: Fa3/1 not a switching port.
Native6506(config-if)#
Native6506(config-if)#
Native6506(config-if)#
Native6506(config-if)#exit
Native6506(config)#int fa 3/1
Native6506(config-if)#switchport
Native6506(config-if)#switchport access vlan 20
Native6506(config-if)#ip address 10.1.1.1 255.255.255.0
% IP addresses may not be configured on L2 links.
Dave
> Joe
-- David Madland CCIE# 2016 Sr. Network Engineer Qwest Communications 612-664-3367"You don't make the poor richer by making the rich poorer." --Winston Churchill
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