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Network Load Balancing with KCS SMTP-Based Links (MX7, SM, MFP, SC7)

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Use of Microsoft Network Load Balancing clusters with SMTP-Based Links on KCS 9.x and above

  • Setup of NLB-Cluster with one Link using only one Network-Interface.
  • Setup of NLB-Cluster with 2 or more Links using different NICs (Network Interface Controller), one is using NLB, others do not use it.


Customer uses TC/Link-MX7 and TC/Link-SM without NLB because of alternative IP-Addresses inside the applications and TC/Link-MFP with NLB because most MFPs do not support multiple server-addresses.

Setup of the Network interfaces for only one NIC (with NLB) (Reference attached NLB-Setup PDF for screenshots)

  • Step 1: Configure NIC-Card LAN-Properties Internet Protocol / IP Settings
    Add the Cluster IP Address to every server inside the NLB-cluster
    The Cluster IP Address must be higher then the dedicated addresses of every server
    The Cluster IP Address must be in the same subnet as the dedicated addresses
  • Step 2: Configure NIC-Card LAN-Properties for Network Load Balancing (checkbox) on every server inside the NLB-cluster
  • Step 3: Configure Load Balancing Properties / Cluster parameters
    Full Internet DNS-Name of the cluster
    Cluster operation mode: Multicast (not default)
  • Step 4: Configure Load Balancing Properties / Host Parameters
    Different Host-Priority for every server
    Dedicated IP-Address for each server
  • Step 5: Configure Load Balancing Properties / Port Rules
    Specify the Port-Range (default port for SMTP is 25)
    If you use more than one port you have to create more specific rules.
    It is not possible to use a rule with more than 1 port (e.g. 25 to 26) !!!
    Specify the protocol (default for SMTP is TCP)
    Filtering mode: multiple host, Affinity: none, Load weight: equal (checkbox)
  • Step 6: Modify the Registry HKLM/Software/WOW6432Node/Topcall/TCLinkxx/TCLSM on every server
    OwnIPAddress: <Cluster IP-Address>
    NLBPortControl : 1

After starting TCSRV you can see in the KCS Monitor for the NLB-Link NLB port control running (Port: <port-number>).

Setup for all other Network interfaces with one ore more IP-Address on each NIC (without NLB)

  • Configure the NICs without Network Load Balancing checked
  • Define one or more IP-Addresses for every additional NIC
    It is possible to connect an additional NIC to the same physical network as the Cluster-NIC
    The IP-Address must be different (smaller or bigger than the Cluster-IP) and different to all other IP-Addresses

After starting TCSRV you can see in the KCS Monitor for the NLB-Links: NLB port control running (Port: <port-number>)
Non-NLB-Links: without the line above.

Level of Complexity 



Applies to  

Product Version Build Environment Hardware
Kofax Communication Server All   W2008, W2012, W2019  



Keywords: SMTP, Network Load Balancing, Cluster, NLB


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