Resources for best practices on creating primary and secondary core

[Jonnyballgame34]

Greetings,

Hoping someone can point me in the right direction for resources for design question.  

Have a site A, that is going to be incrementally moved to site B.  So the WAN connection will be at site A, and connected to Site B via layer to fiber. 

Site A has a 3750 core switch, Site B will get a new 3850.  I want to set it up so that the 3750 is my core switch as long as the Wan circuit is at site A.  When the Wan circuit is moved to site B, I want to be able to swap it so that the 3850 at site B is the active core.  Then eventually as the balance of the equipment is relocated, site A will just go away.  

Been suggest I can use HSRP, but there are concerns with that....Bascially I"m just looking for a good starting point.  Thanks

[Jon Marshall]

Not really enough information.

What do you mean by core ie. what connects to the 3750 in terms of access switches, WAN and internet, servers etc.

Is the link between sites going to be up as soon as the 3850 become active ?

How many vlans etc. etc.

Without knowing how everything currently works it's difficult to make any suggestions.

Jon

[Jonnyballgame34]

HI, 

Thanks very much for looking at my question.  For some reason I didn't receive an alert so I thought I received no replies. 

Information is

Call old site A new site B

-We are waiting for 2 fiber connections at Site B.

--a layer 2 connection between the sites.

--a new 80mb internet circuit at site B.

-old site 3750 has 8 vlans, and connected is

-9-11 access switches,

-DMZ 

-Not sure of server count but I believe at least half a dozen

-80 Wan connection. running DMVPN.

New site will have similar architecture

-3850 and comparable number of access switches. 

-the LAN at the new site will be completely installed before the L2 fiber between sites is active.  

-In addition to the temporary L2 fiber connection between sites, we are waiting on a new

What we are trying to accomplish.

-Install new LAN at site B.  Connect it to core at Site A so it is essentially a single site.  

-Use the 3750 at site A as the primary core, (which it is now), and the 3850 at site B as a backup core

-When the 80mb internet line is installed at site B, we will bring up the circuit, test it. When we are sure it is good, we will re-port the public IP's from the old site to the new site and move the DMZ.  At this point we want to change the LAN so that the 3850 at site B is now the primary core, and the 3750 is now the backup core.  

-Eventually decommission site A. 

The larger goal is to relocate a large site in pieces with minimal disruptions.  We chose this method because it wasn't reasonable to move it all at once. 

[Jon Marshall]

So are you proposing to use completely new vlans/IP subnets at the new site or are you trying to migrate the IP addressing as well ?

Jon

[Jonnyballgame34]

Again, thanks for replying. 

The purpose of doing it this way is to keep the IP scheme so we don't have to move it all in one shot.

[Jon Marshall]

Then HSRP may well be your best option although it could mean a lot of going back and forth between the sites depending on where the source and destination IPs are.

Can you explain what your concerns are with that setup ?

Also is it accurate to say that you cannot move a whole vlan/IP subnet at a time ie. there will be a time when the same vlan is active in both sites ?

Jon

[Jonnyballgame34]

HI,

Sorry, I missed your last reply.

Yes, same Vlans will be active at both sites at the same time.  The concern is because of that there might be a problem with DHCP addresses being handed out by both cores. Thanks

[Jon Marshall · Accepted solution]

Not sure I understand the concern.

You could simply have the DHCP scope on the existing core switch and so any migrated clients go across the interconnect to get their IPs.

Or if you wanted to have each core hand out IPs for the same vlan/IP subnet just have each core responsible for half the subnet.

Or is there something I have not understood ?

Jon