A client is running an MPLS network. Sites A, B and C. Site A is the Head office. Site C is their Disaster recovery site. When doing DR testing for site A, the customer restores their main systems (with IP addresses as their live machines). They are now located in site C but with the potential for duplicate IP addresses appearing if the DR machines are connected up to the MPLS network. Is there any approach that would enable them to have their DR machines accessible for some users in sites A & B when the DR test is happening? TIA.
the basic approach always looks really good, but often you trip over the little details of side effects when you have 2 machines with the same IP - ie. "of course no one will ever have both servers on the network at the same time".....
it is much easier if you can have logical services where you switch logically and dont need to tamper with IP addressing rules- ie by steering load balancers or DNS tables to the alternate config.
so - ignoring the above comments...
split out the server farms at the 2 sites with the main and D/R server sets from any user connections and put servers on different subnets to other devices (this implies you need a layer 3 backbone in each site to give high speed connectivity when users want to get to their local servers).
when you "do" a D/R then only switch over the server segments.
NB - you may want to run a routing protocol on any layer 3 switches that talks to the MPLS edge routers - that way you can alter the routing to logically switch a server subnet to the other site without needing to co-ordinate manual config changes from the MPLS operator.
a couple of times when this has come up the high level idea looks very simple, but the actual requirement has been more complex. EG the D/R servers do double duty, or have management connections etc. In these cases the servers probably need links to the "server" segment and other connections on a different subnet, so you can switch published services, but still have access thru a different connection.
This also makes remote site D/R switching possible, which probably cuts the time and hassle for D/R & testing.
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