We have an ASN with 2 /24 public ip address, one subnet advertise by bgp to ispA and the other to ispB.
We have a plan to deploy a DR site, to have an active/active active/standby access from the internet to our dc, what the approach or option do i have ? do a 'streteched metro link' and this is for all Edge Router so the all my bgp router have full mesh connection from siteA or siteB is a good option, And off course i have another Metro Link Connecting the Data Center ? or i have to request another 1 or 2 /24 public ip address ?
Either can work, it really depends on how you want the DR site to function.
failover the advertisement of the existing prefixes
Active/Active advertise the same prefixes
change DNS during failover to different prefixes
method used and frequency of data updates for applications
bandwidth and time needed for those transfers
Method of failover for the applications
Once you decide on the network and application failover methods then you can design the Data center intereconnect and networking stategy for your needs.
I am not sure that I understand the question. There is no issue at all with using your assigned ASN to different carriers and at different physical locations. This data is simply added to the routes that you advertise.
The issue that I think you are dealing with is what to do when you advertise the same network from two different physical locations. This generally means that your application infrastructure and your internal routing at the two locations need to know what to do with that particular application traffic.
The option that you mention is to have a direct internal connection between the two sites. This can be a metro ethernet as you mention. Or it could be some kind of internal tunneled connection over the internet that allows you pass the relevant traffic internally between the sites.
Other options might be available from your application owners based on the type of data being served and how that data or applications work. If this is some kind of read only public system and updates are rare or can be peridodic completely disconnected hosting is possible.