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Vlan ip addressing

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limejudo

Technical User
Aug 4, 2004
110
US
Once you configure a VLAN on a switch, where does that vlan get it's ip from? Do you use a router or RSM card and creat vlan interfaces with an ip address range?

thx

Eric - A+, Net+, INet+ CCNA next week.
Network Admin/Helpdesk II
 
Yes you would have to have a router or l2/l3 switch with a layer 3 address assigned to it . Any ip assigned to a layer 2 switch only is for manageing the switch and nothing else . With a router just configure an interface and plug it into a port on the switch . With an rsm that is a different story , you get into createing layer 3 svi's on the rsm side then assigning vlans on the layer 2 side for your conenctions.
 
Ok. I see. So I can create 10 vlans on a layer 2 switch that't trunked to a router, but on the router I would need to create 10 subint for each vlan.

But how would the vlan know which interface to pull the ip address from? "encap dot1q vlan 3 native", maybe?




Eric - A+, Net+, INet+ CCNA next week.
Network Admin/Helpdesk II
 
Yes the 'encap dot1q vlan' command is the 'link' between router and switch to indicate which sub-interface (and therefore IP address) on the router is related to which VLAN on the switch. The 'native' identifier need not be specified on every sub-interface - just on the interface which is te native VLAN for the trunk port (i.e. the VLAN that is untagged)
 
Got it, thanks. Been looking threw the Cisco Cookbook and it explained it again.

Thx guys.

Eric - A+, Net+, INet+ CCNA next week.
Network Admin/Helpdesk II
 
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