Flat Network to VLAN switched Network

[jhalterman805]

I am in the process of putting together a plan to implement vlans on flat (vlan1) network.  Currently we are running a flat network (192.168.0.0/16) with 2 remote sites connected via DS3 ATM point to point circuits.  On my LAN interfaces at the remote sites can I use a secondary subnet for the new IP space until i get all hosts moved off the old subnet?  I will be moving to (172.31.0.0/16)? For example:

[Ashley Georgeson]

Hi James,

Your secondary IP address idea should work, but remember the new IP addressing would live in the same old VLAN and you would not be able to use it again on a new VLAN interface.

Another thing to consider is whether you have users/applications that  require to be on the same Layer 2 segment to operate - I would do a  quick analysis of all enterprise applications to to make sure.

You could share the VLANs created at the central site to the remote sites using VLAN trunks, but this is not a design I would recommend.

Have you not considered using Layer 3 links to your remote sites rather than Layer 2 links?  This would take out any Spanning Tree dependencies and make for a more manageable design.  You could then allocate each site a certain address range and summarise the networks to simplify the routing topology.

e.g.

HQ: 172.16.0.0/16

Remote Site 1: 172.31.1.0/24

Remote Site 2: 172.31.2.0/24

(Future) Remote Site x: 172.32.x.0/24

You could provide each site an address range that can cope with existing addressing requirements and any feasible future growth.

Regards, Ash.

[burleyman]

Here is a setup we chose to use to help in troubleshooting and segmenting and scalability.

We use the 10.0.0.0

The second octet we use as the office identifier.

10.1.0.0 - Main office

10.2.0.0 - Branch office, Say Boston

10.3.0.0 - Branch office, Say San Francisco

and so on.

The third octet we use as the type of equipment.

Third octet = 1 it would be as follows

10.1.1.0 - Network gear in the main office

10.2.1.0 - Network gear in the Boston Branch office

Third octet = 3 it would be as follows

10.1.3.0 - Servers in the main office

10.2.3.0 - Servers in the Boston Branch office

Third octet = 5 it would be as follows

10.1.5.0 - Printers in the main office

10.2.5.0 - Printers in the Boston Branch office

Third octet = 1xx it would be as follows

10.1.112.0 - Data for the 12th floor in the Main office

10.2.109.0 - Data for the 9th floor in the Boston Branch office

Third octet = 2xx it would be as follows

10.1.212.0 - VoIP for the 12th floor in the Main office

10.2.209.0 - VoIP for the 9th floor in the Boston Branch office

This helps if we do some wireshark captures we can filter easily. We can also easily filter traffic or engineer it over different paths, limit bandwidth etc.

I think you can see the pattern.

Mike

[jhalterman805]

Thank you guys for the replies.  Great recommendations!  Also I have a current 192.168.0.0 network in place and need to keep it in place and run the new and old in parrallell.   What would be a good way to accopmlish this with my current setup?