Ah another one of those I wish I had F5 or foundry..nope sadly no have to rely on the fake load balancing of MX in my case... :)
Thank you and have a splendid day! Kind Regards, Freddy Hartono Group Support Engineer InternationalSOS Pte Ltd mail: [EMAIL PROTECTED] phone: (+65) 6330-9785 -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Derek Harris Sent: Tuesday, December 13, 2005 3:39 AM To: [email protected] Subject: RE: [ActiveDir] [Way OT] DNS MX load balancing questions... Are both (all) of your mailservers at the same location? If so, you can do a better job of load balancing or failover using a router. Cisco IOS lets you fine-tune it pretty well. -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Sunday, December 11, 2005 9:00 AM To: [email protected] Subject: RE: [ActiveDir] [Way OT] DNS MX load balancing questions... In the first scenario, all 3 servers CAN be used at any time. In the second scenario, mail3 will be used ONLY if mail1 and mail2 stop responding. Scenario 1 balances the load (not evenly, mind you) across the 3 servers. Keep in mind that the "balancing" act only means that IF 3 external servers asks for your MX, they will see that all 3 are of equal weight and MAY choose any one of the 3 to send to. In an ideal world, externalserver1 will choose mail1, externalserver2 will choose mail2 and externalserver3 will choose mail3 and the load will be truly balanced. Well, we are not there yet. In reality, nothing stops all 3 external servers from sending to mail1 or mail2 all at the same time. Also, bear in mind that, although you have 3 equally-weighted MX, an external server will choose one of the 3 and continue to send to that chosen one until that one stops responding. The fact that you have 3 equally-weighted servers does not mean that the external server will use each of them equally or sequentially. Wrt the issue I mention, it is NOT an Exchange problem per se. It is an MS SMTP issue. Here's a reference http://support.microsoft.com/default.aspx?scid=kb;en-us;837993. Can't find a more detailed discussion of it at this time. Sincerely, Dèjì Akómöláfé, MCSE+M MCSA+M MCT Microsoft MVP - Directory Services www.readymaids.com - we know IT www.akomolafe.com Do you now realize that Today is the Tomorrow you were worried about Yesterday? -anon ________________________________ From: [EMAIL PROTECTED] on behalf of Freddy HARTONO Sent: Sat 12/10/2005 5:40 PM To: [email protected] Subject: RE: [ActiveDir] [Way OT] DNS MX load balancing questions... Hi Deji Thanks for the replies That means it makes no sense to invest in having 1 backup MX of lower priorities? So basically what I need is as below? Mydomain MX 10 mail1.mydomain.com MX 10 mail2.mydomain.com MX 10 mail3.mydomain.com Instead of Mydomain MX 10 mail1.mydomain.com MX 10 mail2.mydomain.com MX 100 mail3.mydomain.com? Since with all 3 of the same priorities, if any of the mail is down (mail2) for example, it will retry to mail1 and mail3 automatically according to RFC? Do you happen to have the KB of the exchange issue mentioned below, just wanted to readup on that bug somehow :) Basically we're trying to purchase spam/virus gateways in front of exchange, and I had the idea that it needs to be 3 appliances (2 for load balancing, 1 for backup). Thank you and have a splendid day! Kind Regards, Freddy Hartono Group Support Engineer InternationalSOS Pte Ltd mail: [EMAIL PROTECTED] phone: (+65) 6330-9785 -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Sunday, December 11, 2005 12:31 AM To: [email protected] Subject: RE: [ActiveDir] [Way OT] DNS MX load balancing questions... >>> RFC 2821 requires a mail server to choose MX records randomly when >>> the records are the same priority, but to try all if the initial one chosen doesn't work (until it finds one that does work or the pool is exhausted). Correct. There was, however, an issue early this year (or was it late last year?) where 2K3 SMTP servers were failing to fail over to the next available SMTP servers on the list they receive from a target DNS server. I think this was corrected with a hotfix, but the issue will still exist in a gold, un-hotfixed version. >>>The above means it will try MX of other priorities right (not the >>>other of the same priorities correct?) - sorry just not having a clear word by word answer in the RFC document itself. It will continue to use the highest one, until that one stops responding. As long as the highest-prioritized one continues to accept emails, the originating server will have no need to try another one. HTH Sincerely, Dèjì Akómöláfé, MCSE+M MCSA+M MCT Microsoft MVP - Directory Services www.readymaids.com - we know IT www.akomolafe.com Do you now realize that Today is the Tomorrow you were worried about Yesterday? -anon ________________________________ From: [EMAIL PROTECTED] on behalf of Freddy HARTONO Sent: Sat 12/10/2005 7:07 AM To: [email protected] Subject: RE: [ActiveDir] [Way OT] DNS MX load balancing questions... Hi Michael Thanks for the quick reply. RFC 2821 requires a mail server to choose MX records randomly when the records are the same priority, but to try all if the initial one chosen doesn't work (until it finds one that does work or the pool is exhausted). The above means it will try MX of other priorities right (not the other of the same priorities correct?) - sorry just not having a clear word by word answer in the RFC document itself. One of my vendor is giving me a whitepaper from barracuda appliance that explains how its done, but mentioned that with MX listing below it will provides load balancing AND redundancy (crap to me but now im getting confused myself) http://www.barracudanetworks.com/ns/downloads/Barracuda_WP_MX_Load_Balancing . pdf Is it recommended that the TTL for the domain be set to 0 when using this MX load balancing method? Thank you and have a splendid day! Kind Regards, Freddy Hartono Group Support Engineer InternationalSOS Pte Ltd mail: [EMAIL PROTECTED] phone: (+65) 6330-9785 ________________________________ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Michael B. Smith Sent: Friday, December 09, 2005 8:52 PM To: [email protected] Subject: RE: [ActiveDir] [Way OT] DNS MX load balancing questions... You should have two separate MX records @ IN MX 10 mail1.mydomain.com. @ IN MX 10 mail2.mydomain.com. Mail1 IN A 10.1.1.1 Mail2 IN A 10.2.2.2 RFC 2821 requires a mail server to choose MX records randomly when the records are the same priority, but to try all if the initial one chosen doesn't work (until it finds one that does work or the pool is exhausted). Your proposal below has the problem you describe. ________________________________ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Freddy HARTONO Sent: Friday, December 09, 2005 7:43 AM To: [email protected] Subject: [ActiveDir] [Way OT] DNS MX load balancing questions... Hi All Was just trying to understand something and am getting conflicting results.. If I set the following (or 2 mx of the same priority with 2 differnet a records) Mydomain.com MX 10 mail.mydomain.com Mail.mydomain.com A 10.1.1.1 Mail.mydomain.com A 10.2.2.2 I understand that will provide dns roundrobin but what happened if I shutdown 10.2.2.2, will I lose (logically) 50% of my mail as I do not have another fallback MX?? My understanding is that it does so as the sender mail server will cache the MX record and A record and will only send to there, am I right or am I getting this wrong? If I'm shutting down 10.2.2.2, will the sender mail server retries to 10.1.1.1? (lets assume there's no ttl reconfig to zero) Thanks lots Thank you and have a splendid day! 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