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Exchange 2010 Send Connector failover (automatic or manual)

    Question

  • Hi Guys,

    I have 2 send connectors on my Hub transport server. Both connectors have 2 different costings configured on the address space of 50 and 100 respectively. When the primary connector cannot send to my EDGE server, it sits in a retry state till it eventually NDRs. If I manually Disable or Suspend the connector then exchange uses the second connector to my second EDGE server. At which point shoud the connector failover? How do I configure it to failover automatically? I assume by configuring different costings Exchange should automatically failover between the connectors but this isn't happening. 

     

    Tuesday, January 18, 2011 11:31 PM

Answers

  • You’re describing a scenario where two connectors have been created like this:

     

    new-SendConnector -Name 'Connector-A' -Usage 'Custom' -AddressSpaces 'SMTP:*;10' -IsScopedConnector $false -DNSRoutingEnabled $false -SmartHosts 'smarthost-a.domain.com' -SmartHostAuthMechanism 'None' -UseExternalDNSServersEnabled $false -SourceTransportServers 'Srv1'

     

    new-SendConnector -Name 'Connector-B' -Usage 'Custom' -AddressSpaces 'SMTP:*;10' -IsScopedConnector $false -DNSRoutingEnabled $false -SmartHosts 'smarthost-b.domain.com' -SmartHostAuthMechanism 'None' -UseExternalDNSServersEnabled $false -SourceTransportServers 'Srv1'

    One would think this makes a round-robin or otherwise load balanced scenario.  It does not.  See these two quotes here:

     

    “When a message is sent to an external recipient, Exchange 2010 will always select a single connector through which to send the message”

    à

    “If more than one connector meets the address space match criteria, Exchange 2010 routing evaluates the following criteria to select a connector:

    1.     Connector cost   The cost of the connector is the sum of the cost assigned to all the IP site links between the source Active Directory site and the Active Directory site that contains the source servers for the connector, and the cost assigned to the connector. The connector with the lowest aggregate cost is selected. If more than one connector has the same cost, the selection process continues to the next step.

    2.     Proximity   The source server that has the closest proximity to the routing server is selected. This means that the local server is chosen over another Hub Transport server in the same Active Directory site, and a server in the local Active Directory site is chosen over a source server in a remote Active Directory site. If more than one connector matches the criteria, the selection process continues to the next step.

    3.     Alphanumerically lower connector name   If more than one routing path has the same cost and proximity, the connector with the name that has the lowest alphanumeric value is selected.”

     

     

    Source: http://technet.microsoft.com/en-us/library/bb232045.aspx

    This means rule 3 would apply.  Use an MX record(s) as stated above to achieve load balancing on a send connector.

     

     



    Mike Crowley
    Check out My Blog!

    Saturday, January 22, 2011 8:32 PM
    Moderator
  • Hi,

    That's by design in Exchange 2010 which is same as Exchange 2007 even though Exchange 2003 is feasible.

    Exchange 2007 routing has been changed and if a connector with the same address space goes down messages will continue to that connector until there is a change like cost.

    Thanks

    Allen


    Allen Song
    Tuesday, January 25, 2011 9:05 AM
    Moderator

All replies

  • You have found the annoying little secret about send connectors.  After a address space is chosen, the other connectors don’t matter. 

    Two comments:

    ·         The default edge subscription connectors have -- as their server.  this means they load balance by default.

    ·         If you don’t use edgesync and just want to use your edge server and another non-edge server gateway, use an mx record:

    o   In the smarthost settings of your “to internet” connector fill it in with mx.domain.com

    §  Create an mx record(s) with two server names in it.

     

    It’s not overly clear in the dialog box that the entry can be a host or an mx record



    Mike Crowley
    Check out My Blog!

    Wednesday, January 19, 2011 5:29 AM
    Moderator
  • Thanks for the reply Mike. So what your saying is as soon as I setup different costings on my address space of * (for all outbound internet email) that Exchange will only ever try and use that connectors since it's got the lowest cost, unless I manually intervene and disable/suspend the connector?

    Friday, January 21, 2011 3:53 AM
  • You’re describing a scenario where two connectors have been created like this:

     

    new-SendConnector -Name 'Connector-A' -Usage 'Custom' -AddressSpaces 'SMTP:*;10' -IsScopedConnector $false -DNSRoutingEnabled $false -SmartHosts 'smarthost-a.domain.com' -SmartHostAuthMechanism 'None' -UseExternalDNSServersEnabled $false -SourceTransportServers 'Srv1'

     

    new-SendConnector -Name 'Connector-B' -Usage 'Custom' -AddressSpaces 'SMTP:*;10' -IsScopedConnector $false -DNSRoutingEnabled $false -SmartHosts 'smarthost-b.domain.com' -SmartHostAuthMechanism 'None' -UseExternalDNSServersEnabled $false -SourceTransportServers 'Srv1'

    One would think this makes a round-robin or otherwise load balanced scenario.  It does not.  See these two quotes here:

     

    “When a message is sent to an external recipient, Exchange 2010 will always select a single connector through which to send the message”

    à

    “If more than one connector meets the address space match criteria, Exchange 2010 routing evaluates the following criteria to select a connector:

    1.     Connector cost   The cost of the connector is the sum of the cost assigned to all the IP site links between the source Active Directory site and the Active Directory site that contains the source servers for the connector, and the cost assigned to the connector. The connector with the lowest aggregate cost is selected. If more than one connector has the same cost, the selection process continues to the next step.

    2.     Proximity   The source server that has the closest proximity to the routing server is selected. This means that the local server is chosen over another Hub Transport server in the same Active Directory site, and a server in the local Active Directory site is chosen over a source server in a remote Active Directory site. If more than one connector matches the criteria, the selection process continues to the next step.

    3.     Alphanumerically lower connector name   If more than one routing path has the same cost and proximity, the connector with the name that has the lowest alphanumeric value is selected.”

     

     

    Source: http://technet.microsoft.com/en-us/library/bb232045.aspx

    This means rule 3 would apply.  Use an MX record(s) as stated above to achieve load balancing on a send connector.

     

     



    Mike Crowley
    Check out My Blog!

    Saturday, January 22, 2011 8:32 PM
    Moderator
  • Hi,

    That's by design in Exchange 2010 which is same as Exchange 2007 even though Exchange 2003 is feasible.

    Exchange 2007 routing has been changed and if a connector with the same address space goes down messages will continue to that connector until there is a change like cost.

    Thanks

    Allen


    Allen Song
    Tuesday, January 25, 2011 9:05 AM
    Moderator