network migration

[Hisoma Sama]

Hi

we have an old network with collapsed core design using one vlan with /16 subnet

the plan is to upgrade to new cisco generation switches with Core-Distribution-access layer with routes access layer

what's the best plan for this migration to make it with less downtime as possible 

if any documents or video can be share i would appreciate it 

thanks

[rais]

I hope you have considered spine-leaf architecture before deciding on access-distro-core.

Thanks

[Hisoma Sama]

can you tell me more about spine-leaf? im not familiar with the term

[balaji.bandi]

A couple of Questions :

Core-Distribution-access layer   - is this a fully new set up or you want to use an exiting Access switch to the new Core switch?

For now, your Access Layer is Layer 2 connected to Collapsed Core ( Gateway reside 1 VLAN in Core)

You want to /16 make a small subnet and make Access Layer are Routed? instead of Layer 2?

Option1 :

If you like to migrate the existing environment to a new environment 3 tier design.

Build 3 tier design best as per cisco CVD 

Connect to exiting core with Layer 2 port-channel

Move to Layer 3 Interface to New core Switch ( small Network blip due to network convergence and new Gateway )

Option2: Planning to build Routed Access layer

Identify unused subnet in /16

start making a smaller subnet for each access Layer

take a new Subnet of RFC 1918 for point to point link with OSPF is best i can see here.

make access layer with a dual uplink to distribution

Migrate the user connections to the new switch ( here user will get new subnet) - hope this is acceptable or you looking same old IP address?

Note: Start making a small Network Digram understand yourself how your migration plan and approach before you plan anything.

So you have pictures of what cables to move when?

Share with us any other suggestion required 

[Hisoma Sama]

check my answers and notes below

A couple of Questions :

Core-Distribution-access layer   - is this a fully new set up or you want to use an exiting Access switch to the new Core switch?

(answer ) new set up 

For now, your Access Layer is Layer 2 connected to Collapsed Core ( Gateway reside 1 VLAN in Core)

You want to /16 make a small subnet and make Access Layer are Routed? instead of Layer 2?

(answer) setup new cisco SW's and routed access layer

Option1 :

If you like to migrate the existing environment to a new environment 3 tier design.

Build 3 tier design best as per cisco CVD 

Connect to exiting core with Layer 2 port-channel -----> if i did this wont messed up with ip plan ( im looking for similar scenarios online i couldn't find do you know if there is any? just to have clear picture how its done

Move to Layer 3 Interface to New core Switch ( small Network blip due to network convergence and new Gateway )

Option2: Planning to build Routed Access layer

Identify unused subnet in /16

start making a smaller subnet for each access Layer ----> but i plan for new ip scheme the old ip wont be used anymore

take a new Subnet of RFC 1918 for point to point link with OSPF is best i can see here.

make access layer with a dual uplink to distribution

Migrate the user connections to the new switch ( here user will get new subnet) - hope this is acceptable or you looking same old IP address?

Note: Start making a small Network Digram understand yourself how your migration plan and approach before you plan anything.

So you have pictures of what cables to move when?

[balaji.bandi · Accepted solution]

start making a smaller subnet for each access Layer ----> but i plan for new ip scheme the old ip wont be used anymore

This makes life easier. if you like to use a new subnet altogether with the new setup. (this time make sure you plan your IP schema, not like /16 subnet you had before) looking at least the next 5 years you not going to change majorly in terms of IP schema, and reserved for future use.

here is my Option:

1. Build a totally new Setup and Isolating from Old Setup. 

2.  Make sure all your CORE / Dist / Access works as expected

3. I mean Router Access Layer until core, test your redundancy.

4. Once you happy, then build Layer 3 Peering between  OLD CORE and NEW CORE and run any IGP your favorite to learn the route exchange between CORES

5. Move the user's leased Effect to the new Access switch or Test users to move to the new Access switch test the connection other stuff.

6. Once you users activity tested (like internet, email, application)

7. Start moving the users from the old switch(access) to the new Access switch slowly area or group at a time, keep monitoring the network

8. as you learn lessons you can speed up the migration if no issue reported in the new environment.

If this is large-scale deployment, consider SD-Access with DNAC to make life easier, see some offers now DNAC is a free single node.

Note: Start making a small Network Digram understand yourself how your migration plan and approach before you plan anything.

So you have pictures of what cables to move when?

[Hisoma Sama]

Hi Balaji

thank that was so helpful 

another question about migrating cisco WLC and AP?

since it will be the AP different subnets and will be reached to WLC through IGP

is it working scenario? 

[balaji.bandi]

As Long as user subnet same, it can have roaming with same SSID

AP can be in any subnet underlay, as long as they can reach WLC ( as i said before).