Migration Approach

[IslamOmar]

Hi ,

I have network migration project which we will migrate an old legacy network ( traditional L2 design ) where access switches are connected with trunks up to core ( some are connected direct to the core switch :-O )
All gateways are configured in core with HSRP running in between ( 6800 series ) . OSPF is running on all gateways and between Core & FW to route the traffic from LAN campus to outside network

Challenge is that existing access switches cabinets can't accommodate new and old so that i can setup in parallel the old with the new network .

So my approach to migration will be as follows :

1- Installing / staging the new core ( VSS ) and new distribution ( verify the connectivity in between )
2- Connecting the old with the new core via L3 link and enabling OSPF in between
3- Start migrating building by building ( shifting end points from old to new switches where i will keep two gateways ( old / new core ) till replacing all old access switches and shutting down all old gateways from old core
4- After migrating all access , Will shift all connectivity from old core to new .

Any suggestions , ideas ?

[Dennis Mink]

what have you got so far?  this forum is not for spoon feeding, please tell us your ideas and plans and we will help you with that

[IslamOmar]

I think i have shared my ideas

[balaji.bandi]

On High level your plan seems to be reasonable.

But you have not mentioned, is the existing Core also VSS or Traditional L3 ?

As long as you have all links are dual attached uplinks, your migration plan is easy.

Make sure you make high level network diagram, and STP mitigation plan (if L2 incolved).

Where ever required make sure you clear the ARP. somce legacy stuff still stuck in ARP table.

[IslamOmar]

The current core is traditional L3 with HSRP running in between for all gateways ..
Thanks

[paul driver]

Hello

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@IslamOmar wrote:

So my approach to migration will be as follows :

1- Installing / staging the new core ( VSS ) and new distribution ( verify the connectivity in between )
2- Connecting the old with the new core via L3 link and enabling OSPF in between
3- Start migrating building by building ( shifting end points from old to new switches where i will keep two gateways ( old / new core ) till replacing all old access switches and shutting down all old gateways from old core
4- After migrating all access , Will shift all connectivity from old core to new .

Any suggestions , ideas ?

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Just like to add you'd probably will require two connections between old/new core( L2 & L3)
1) L2 for the interconnects between closets switches,
L3 for ospf connectivity between old /new core ( advertise a default route from old to new core)

Create L3 svi on new core but have them in a shutdown state

2) Migrate access closets over to the new core (L2)
3) Migrate each L3 svi over to new core by disabling it on the old core, enabling on new core and adverting it in ospf
4) Once all connections have been relocated. shutdown L2/L3 between old new core
5) Relocate wan/Fw connection over to new core, add /receive static default towards Fw/wan egress

[IslamOmar]

Thanks Paul for your inputs , just to let you know that gateways for the access switches will be in the distribution not the new core , so i guess there is no need for L2 between the two cores ....

[paul driver]

Hello

So you are not extending your L2 all your interconnects are L3 correct?

Are you running a collapse core/distribution or separate core - distribution 

maybe share simple topology diagram of your current network design 

[IslamOmar]

The current setup is kinda messed , it's a three tired design but with some access connected to core and some connected to distribution and spanned up to the core ..( its almost all L2 spanned up to the core where all the gateways are there ) .

the proposed new design is three tired multi-layer design ( All access will be aggregated to distribution switches according to their respective buildings ) .. gateways will be in distribution and in between distribution - core ( OSPF will used to route all campus traffic to the core ) .

due to non-enough space in the cabinet to accommodate the new switches , i'm forced to migrate building by building and floor by floor ( with parallel L3 connection between the old / new core ) so that old switches will be able to reach it's GW ( old core ) and new switches will be reaching it's new GW ( new core ) .. L3 will be used to route these traffic to the internet / servers / etc....