How to produce a DR solution

[dan_track]

Hi

I'd like to know how to accomplish the following:

I have two datacentres at the moment. What I'd like to do is convert one into a DR site. Currently our live website points to IP x.x.x.x the equivalent ip on our DR site would be y.y.y.y. The problem that comes up is that if I were to failover to the DR site, my DNS would need to be updated to reflect the change in IP. Is there someway of keeping the same public IP's on the firewalls, switches and routers the same on each site.

Just to add my two sites are BGP'ing with our ISP, so failure on our live site link or router will cause traffic to be sent to the new DR site. Connecting the two sites is our internal LAN link. The two sites are in two different geographic locations.

What problems could you see arising from doing this?

How do places like google manage to move their traffic from live to DR without changing their IP's?

Thanks in advance

Dan

[cisand2002]

Hello Dan,

Can't you have the backup website with same ip address as live/primary web site ? As this will be DR website ?

An other solution is to do nat on DR router of the y.y.y.y to x.x.x.x and advertize it to isp as backup route.

In this case remote sites will see x.x.x.x from primary router when all ok and see x.x.x.x from DR when in backup mode.

HTH,

cisand

[rgodden]

the ciscopress book on content solutions has some examples of the different methods for dual data centres

[dan_track]

Hi

The live site is on a different subnet to the DR site.

Live site:

xxx.xxx.xxx.0/27

DR Site:

yyy.yyy.yyy.0/27

How can I have the same IP on both sites without causing routing problems.

Thanks

Dan

[andrew.gristina]

The classic way to do this is with Global Services Load balancing. Cisco has a GSS product for this type of loadbalancing/failover. What kind of clients hit your site? If it is browser based clients, GLSB is pretty good. If it is server (like B2B), then you probably need GSLB and some Content Switching for when the servers aren't doing new lookups.

If you use BGP and have your own public AS and can advertise the same /24 IP block from both you can do some redundancy tricks, but this is complicated and you can make some bad BGP blackholes or become a transport if you don't know what you are doing. It sounds like you can't do this because you can't advertise /27s to the internet at large with BGP (the smallest denominations are /24), your ISP is probably summarizing.

You can also try anycast IP addressing (but this is also complicated and some applications won't do well with it.)

The last thing is to contract with Akamai or somebody like that to do edge content caching and failover DNS. Expensive but makes it a managed service partly and requires very little upfront investment.

Google uses loadbalancer/content switching farms (netscalar equipment specifically I believe, but Cisco has some good products in that segment as well) with a distributed DNS infrastructure (like Akamai). Google spends a lot of money on this redundancy.

[Iain]

Question: Aren't there some issues with DNS-based solutions. Namely the fact that most clients cache DNS addresses locally. Please correct me if I'm wrong, but wouldn't this cause some major delays in the time it takes to fail over to the secondary (DR) site at IP y.y.y.y?

- Iain