Newbie VLan question...

Answered Question
Jun 23rd, 2008
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Hello,


Im trying to setup VLan's to learn about them for the ccna exam ... and I have a Cisco 1700 router connected to a cisco 2950 switch. Here's my problem.


I went to setup a vlan and noticed that vlan1 was there and all ports assigned to it.


So I created another vlan and then went to bring it up and got disconnected:


Switch2(config)#interface vlan 2

Switch2(config-if)#no ip address

Switch2(config-if)#no shutdown

Connection closed by foreign host.


I can no longer telnet into this switch via the ip address I had set... and can't ping that IP, hwoever I can still ping the machines on the switch.


I'm working remotly from this switch, is it possible to revert the change or regain telnet access?


Correct Answer by Jon Marshall about 9 years 1 month ago

Chris


Firstly your 2950 switch is a layer 2 switch only so you can only have one L3 vlan interface (SVI) active at any one time on the switch. Note you can have multiple L2 vlans just not L3 interface.


By default all ports will be in vlan 1 and there will be a vlan 1 interface on the switch. This vlan interface is used for managing the switch, it does not affect the traffic going through the switch.


The IP address you had set - was this attached to the vlan 1 interface ?. When you tried to bring up the vlan 2 interface did you shut down the vlan 1 interface ?


Looks like you were trying to create another vlan at Layer 2.


Switch2(config)# vlan 2

Switch2(config-vlan)# name v2


The above would create a vlan at L2 and you could assign ports to vlan 2. But you would still need to have a L3 interface for vlan 2.


Does this make sense. It is about the key difference between a L2 vlan and a L3 interface for that vlan. The commands you were using were to create a L3 interface and the fact you are not going to be giving it an IP address suggests you only wanted to create a L2 vlan.


Jon



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Correct Answer
Jon Marshall Mon, 06/23/2008 - 11:13
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Chris


Firstly your 2950 switch is a layer 2 switch only so you can only have one L3 vlan interface (SVI) active at any one time on the switch. Note you can have multiple L2 vlans just not L3 interface.


By default all ports will be in vlan 1 and there will be a vlan 1 interface on the switch. This vlan interface is used for managing the switch, it does not affect the traffic going through the switch.


The IP address you had set - was this attached to the vlan 1 interface ?. When you tried to bring up the vlan 2 interface did you shut down the vlan 1 interface ?


Looks like you were trying to create another vlan at Layer 2.


Switch2(config)# vlan 2

Switch2(config-vlan)# name v2


The above would create a vlan at L2 and you could assign ports to vlan 2. But you would still need to have a L3 interface for vlan 2.


Does this make sense. It is about the key difference between a L2 vlan and a L3 interface for that vlan. The commands you were using were to create a L3 interface and the fact you are not going to be giving it an IP address suggests you only wanted to create a L2 vlan.


Jon



chrish346 Mon, 06/23/2008 - 11:35
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Thanks jon... im going to have to do more reading on L2 and L3 vlans ;) Thanks again!

ravikantgumber Fri, 08/22/2008 - 07:26
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MY FRIEND VLAN INTERFACE CAN B CREATED ONLY IN L3 SWITCHES.. AND 2950 IS L2 SWITCH I THINK U HAV DONE SOME MISTAKE IN ASKING THE QUOSTION CAN U EXPLAIN IT PROPERELY

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