Exchange 2010 sites connectivity problem

I have a client that have Exchange 2010 with 2000 users that's split on two different geographical sites that are connected through MPLS and replicating changes simultaneously. Each exchange site has 4 servers (1 DAG with 2 mailboxes and (2 for CAS and HT).

The client had an IT company that applied the Exchange 2010 project for them thinking they have had redundancy but recently the site 1 had an internet problem (Cable was cut due to construction) and all the users on site1 stopped receiving mails....

That made me wonder how could one solve such a problem and how would Exchange on site 2 detect a timeout for mailboxes in Site1 ... notice that DAG on site 1 doesn't have users on site 2 and vice versa.

Would creating one DAG For all exchange servers handle the problem in case Internet was out in one of the sites? I would appreciate that.

I don't have more information now in regard to the infrastructure .

Thanks.
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Mohammed HamadaSenior IT ConsultantAsked:
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Adam FarageSr. Enterprise ArchitectCommented:
If both sites are active, the recommended architecture for this would be to setup two DAGs (so if you loose a site in theory you would still be online). I wrote an article about site switchover here: exchangelaboratory.com

If you lost email connectivity look at your MX records, and the route for your smarthost. Most likely the MX records are pointing to a single site OR your smarthost is only routing to a single site (or doesn't do a healthcheck over TCP 25).
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Mohammed HamadaSenior IT ConsultantAuthor Commented:
Ah you mean one DAG at each site that includes all of the mailbox servers in all sites ? but if Internet gets disconnected in one site which are active would DAG handle the delivery of incoming and outgoing emails to site 1 or two in case of no internet connectivity available in one of them?

I don't know what's the domain so I can't honestly tell you if the MX records are configured properly or not but I assume they might be correct.  I think MX are pointing to both sites properly but could it be because users are not located in eachsite's Exchange (I mean current DAGs are not including each site's mailbox server).?

thanks
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Adam FarageSr. Enterprise ArchitectCommented:
You would have two spanned DAGs, basically 3 in the primary (active) site and two in the secondary (other Active) site. If you have 10 mailbox servers across two dags, in theory if you loose site connectivity for Site A the Site B DAG will stay online while Site A is offline. When you do the datacenter switchover everyone goes down for a short period of time, but its a more optimal way to running it.
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Mohammed HamadaSenior IT ConsultantAuthor Commented:
I am sorry I couldn't really get that, what do you mean two spanned DAGs, 3 in the primary and two in the secondary site...

What I know now is that the customer have 4 servers in each site! 1 dag in each site with 2 mailbox servers in them and 2 for CAS.

Do you mean I have to create 1 dag in each site that contains all mailbox servers in both sites ?

I would appreciate if you could elaborate more.
thanks
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Simon Butler (Sembee)ConsultantCommented:
A single DAG isn't going to work.
The design I do for this scenario is very simple.
Each location has its own DAG, replicating to one of the other locations.
The passive server for one of the other locations is the FSW for the primary.

So site 1 contains server 1 (DAG site 1) and server 2 (DAG site 2).
Site 2 contains server 3 (DAG site 1) and server 4 (DAG site 2).
Server 2 is the FSW for DAG site 1. Server 3 is the FSW for DAG site 2.
All locations are in their own AD site.
DAC mode enabled.

Net result - the loss of a connection does not result in loss of mailbox access.

Simon.
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hecgomrecCommented:
Sorry but I think the main issue here is to have at least 2 internet connections.

You can have the best solution in place, but if you have no access to the world your best solution won't work.

Having at least 2 WAN is just better for everything.  Of course the best option will be to have 2 different ISP and configure either load balancing or failover one of the two lines.  Here the only thing is to avoid using SMTP relay smarthost as usually they are attached to the ISP public IP which makes outgoing messages bounce back because the sending IP is not allowed to do so with the other WAN if service do goes down.

If there is no way to avoid the relay smarthost maybe having another connector ready but disabled could save the day!!! but also any Admin can go and change the settings of the current connector and put the valid relay server for the operating ISP when needed.
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Mohammed HamadaSenior IT ConsultantAuthor Commented:
@Simon, I checked again and customer is using DAG on each site but the dag includes mailbox servers only on their site not on each so apparently you're right. I'm going to include all the Mailbox servers in both DAGs in each site and do a copy of every database on every mailbox server.

@Hecgomre, I can't really force options on my customer that would cost him lot of money! I will try the DAG option first and will recommend your option for sure but I doubt they'll take it.

Thanks
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Simon Butler (Sembee)ConsultantCommented:
Be sure that you understood my answer correctly.
It is not a single DAG, but multiple DAGs. A server cannot be a member of more than one DAG. Don't try and do something like a single DAG but without copies of every database on every member. I have seen that tried before and it simply doesn't work.

Simon.
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Mohammed HamadaSenior IT ConsultantAuthor Commented:
Yes I understand your point perfectly. thanks a lot.
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Mohammed HamadaSenior IT ConsultantAuthor Commented:
Simon, Do you not recommend that the FSW be on the mailbox servers? Is it not recommended to put the FSW on mailbox role by default? or is there a purpose behind putting them there.

Thanks
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Simon Butler (Sembee)ConsultantCommented:
You can put the FSW anywhere you like, as long as it isn't a member of the current DAG.
I have never seen a recommendation against putting it on a server with the Mailbox role.

Simon.
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hecgomrecCommented:
I still don't get it!!!

If you said
The client had an IT company that applied the Exchange 2010 project for them thinking they have had redundancy but recently the site 1 had an internet problem (Cable was cut due to construction) and all the users on site1 stopped receiving mails....

It really doesn't matter what solution you put for your data/server/backups if you don't have a communication backup.

You can have the best state of the art server/data solution but if everything is base in one connection (cable) your solution in going to fail!!!
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Mohammed HamadaSenior IT ConsultantAuthor Commented:
Hecgomrec
Both sites have Internet connection and both sites are connected to eachother through MPLS, but one time the MPLS had issues and users on secondary site lost connectivity to their mailboxes ... The current configuration is totally wrong since they don't have the correct order of quorum as Simon have suggested it to be setup.

But assuming we have a setup second internet connection on each site and we have the right configuration for DAGs and Quorum too. In case the HQ loses Internet connection and MPLS connection to the second site... How are users on site 2 going to be able to connect to the their mailboxes if it's on the first site?
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Simon Butler (Sembee)ConsultantCommented:
That is why I suggested two DAGs.
Then if you lose the link between the two sites the only people who are affected are those out of their home site.

Simon.
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Mohammed HamadaSenior IT ConsultantAuthor Commented:
Thanks Simon, that's why I accepted your answer! I am fully aware of how the scenario you mentioned works.
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