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New Member

VLAN and IP address

Hello All,

My network comprises with layer 3 switch and managed and un-managed layer 2 switch. I want to separate LAN segment to each VLAN and do not want to change client IP address when client machine move across VLAN. Is it possible? How can I configure?

Please advice too.

Thanks a lot,

Nitass

1 ACCEPTED SOLUTION

Accepted Solutions
New Member

Re: VLAN and IP address

Hello Nitass,

what you are seeking a form of 'dynamic vlan' assignment. Cisco has the older 'VMPS' protocol that basically maps the mac-address to a vlan so no matter where you plug in that machine, it would get the same vlan dynamically. There is also Cisco network registrar software that basically would do assign the vlan dynamically based on a username/password information. Both these methods are pretty old and more importantly, they are Cisco proprietary! so you cannot use any 3rd party switches in your network.

Thesedays, customers use dot1x with dynamic vlan assignment. But that would also involve your host to support dot1x, your switches to support dot1x and you would need a radius server to assign those dynamic vlans.

So as you can see, there ARE options to do what you seek but they are not very simple or straightforward and would require good sound implementation strategy in your network.

8 REPLIES
New Member

Re: VLAN and IP address

Hello Nitass,

One VLAN should have one IP subnet. So you should choose which clients should belong to what VLANS and configure their IP Address accordingly.

Evewn though theorotically concepts like mobile IP can be used in your case, that is not a genrally deployed solution in enterprise like yours with umanaged L2 switches.

So basically, we are stuck with unique ip subnet for each vlans.

New Member

Re: VLAN and IP address

Hello ybajpai,

Thanks for reply.

I have read about ip subnet-based VLAN or layer 3 VLAN feature on some switch vender. How about that feature on Cisco?

Could you please advice me?

Thanks a lot,

Nitass

New Member

Re: VLAN and IP address

Hello Nitass,

Can you clarify what feature you are referring to? All Cisco L3 switches support "subnet-based" vlan and layer3 routing for them.

Regards,

Yash

New Member

Re: VLAN and IP address

Hello ybajpai,

Thanks for reply.

Sorry for my ambiguous question. Could you please read the topic "4) Layer 3 VLAN: Membership by IP Subnet Address" in the following URL?

Virtual Local Area Networks

By Suba Varadarajan

http://www.cse.wustl.edu/~jain/cis788-97/ftp/virtual_lans/

I would like to use this feature with Catalyst switch. Please advice too.

Thanks a lot,

Nitass

New Member

Re: VLAN and IP address

Hello Nitass,

what you are seeking a form of 'dynamic vlan' assignment. Cisco has the older 'VMPS' protocol that basically maps the mac-address to a vlan so no matter where you plug in that machine, it would get the same vlan dynamically. There is also Cisco network registrar software that basically would do assign the vlan dynamically based on a username/password information. Both these methods are pretty old and more importantly, they are Cisco proprietary! so you cannot use any 3rd party switches in your network.

Thesedays, customers use dot1x with dynamic vlan assignment. But that would also involve your host to support dot1x, your switches to support dot1x and you would need a radius server to assign those dynamic vlans.

So as you can see, there ARE options to do what you seek but they are not very simple or straightforward and would require good sound implementation strategy in your network.

New Member

Re: VLAN and IP address

Hi ybajpai,

Thank you very much.

Nice to meet you,

Nitass

New Member

Re: VLAN and IP address

Hi Nitass

you could subnet further, while retaining IP addressing; i.e creating seperate vlans for each newly created subnet. but you need to be carefull with IP conflicts (L3 interface address and Client)

Hope this helps.

nyr

New Member

Re: VLAN and IP address

if the clients are winxp multiple ips per int. are supported. you could assign an ip per-vlan to that one int.

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