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Problem with Vlan creation

Problem: Trying to change IP address and vlan info on a 1760 router and a 2950 series switch. Basic router-on-a-stick configuration. Both devices are located far away and are being accessed through the serial link via telnet. We are copying the config changes from flash to the running config so that we can easily rollback via reboot. The question that I have is what is the best way to create the new VLAN (in this case vlan 10) on the switch so that it communicates properly. Should I just telnet in to the switch first before making any config changes and create the new vlan with the command: 2950(config)#vlan 10 command and then do a copy flash run or is there a way that I can create the new vlan in the config file and save it to flash so that when it is copied over to the running config it is properly created? I would prefer to do the second option if possible. I created this scenario in a lab and after creating vlan 10 via the command: 2950(config)#vlan 10 I looked at the running config and did not see it displayed but when you do a show vlan it is there and working so I am not sure what the commands would need to look like in the file in flash to make this work when it is copied to the running config. Is my only option to create the vlan before the copy flash run?

1 REPLY
Cisco Employee

Re: Problem with Vlan creation

Hi Friend,

When you create a vlan on layer 2 switch you will not see in running config. It will be aded to the vlan.dat file so you need to worry when you create any new vlan.

Since its a layer 2 switch and you are simple creating vlan at layer 2 you will always retain the connectibity because you are not playing with an ip address.

Once your vlan is created it is saved in vlan.dat file and it will automatically be allowed on the trunk if you have not restricted.I am talking of trunk between your switch and your router.

Once done you can create sub-interface on router and assign it an ip adress fr vlan 10 subnet and then issue encapsulation command and finally say "wr mem".

You will be good to go from there. When any remote configuration is done it is always recommended to start from the last device and then come closer to your side and in your case the last device is switch and then router.

Best of Luck.

Regards,

Ankur

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