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New Member

Need to do NAT in the same VLAN


I have 2 servers which work in conjuction, one is database server other is its application server, both servers are in same vlan, ip address of database server is hard coded in application server. Now I have a BCP/DRP site where there is the replica of the database server, now when this database server on the primary site goes down then application server should connect to BCP site database server. I see 1 solution to it but not sure that it would work:

do a NAT of the original database server ip with BCP site database server IP. Would it work and if yes then whether i would b able to perform NATTING of the same IP which is Active once and then when that server goes down.

Thanks in advance



Re: Need to do NAT in the same VLAN


You say both the application server and the database server are on the same VLAN and thus the traffic wouldn't go through the router for any communication between them. Any router solution to provide redundancy would only be applicable if the traffic does traverse through the router itself. Hence, you would have explore some server based solution for this setup.



New Member

Re: Need to do NAT in the same VLAN


1 application and 1 database server are on same vlan and on the same switch and other database server is on different subnet across the WAN to a remote site.


New Member

Re: Need to do NAT in the same VLAN

Hi there,

you could use a CSS (in the bridged mode);

-IP of DB server would be VIP address sitting on CSS

-IP address of DB server A would re-assigned

-CSS would then monitor status of both DB servers.

-APP server would still be pointing to old address (but VIP sitting on CSS)


New Member

Re: Need to do NAT in the same VLAN

Mr. Hakeem

Could you explain litle further, what is css..?

Thanks and Regards

Re: Need to do NAT in the same VLAN


CSS is content server switches, specifically meant for providing a fault tolerance services to the servers transparently.

In your setup, even if the DB server goes down, you cannot have the same ip address assigned to another Server across somewhere in WAN, which may cause routing anamolies.

Also as pointed out by one of the previous poster, your APP server will always tries to arp for the DB server ip, as it is also sitting on the same subnet.

In your case, you should probably look at other alternatives.

1) the app server should be intelligent enough to address DR redundancy scenarios.

2) App server should be configured to do name/dns resolution to resolve the DB server ip. The ip should not be hardcoded in to the app server.

In this case, when th server goes down, you can change the DNS/name server entries suitably to point to the redundant server.

3) You should also think about both the app server/ db server going down.( in case of any issues with the whole site).

In this case, clients should connect to the redundant setup altogether.

Clearly speaking this should be investigated indepth before resorting to some sort of adhoc solutions.

I suggest you to do a thorough assesment of all points on DR redundancy in your case.


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