Knowledge Base

The issue can be caused by identical IP addresses at each end of the channel, IP addresses in different subnets without static routing at each end of the channel, or a channel NIC configured for DHCP when a DHCP server is not available.

During the installation of VMware vCenter Server Heartbeat, some configuration data from the Primary server is copied to the Secondary server. This includes configuration information for any NICs. The Help text displayed on the VMware vCenter Server Heartbeat Setup wizard describes how to configure the IP address for each NIC on the Secondary server. If this step is not completed, it is possible for one or more channel NICs on the Secondary server to contain a variety of incorrect addresses derived from the Primary server.

For example, follow the correct configuration after deployment:

Primary

Public NIC: 192.169.1.101
Channel NIC #1: 9.0.0.1
Channel NIC #2: 10.0.0.1

Secondary

Public NIC: 192.169.1.101
Channel NIC #1: 9.0.0.2
Channel NIC #2: 10.0.0.2

1. 192.169.1.101
2. 9.0.0.1
3. 10.0.0.1
4. No static IP address (i.e. NIC is configured to use DHCP)

None of these allow a connection to address 9.0.0.1 on the Primary server - (a) and (c) are in a different subnet, (b) is a duplicate IP address, and (d) fails because there is normally no DHCP server connected to the channel NICs.

The address that is assigned to Channel NIC #1 on the Secondary server depends on the exact driver configuration of the NICs on that server, as compared with the NICs on the Primary server. The result expected during deployment, is for the IP address of Channel NIC #1 on the Primary server to be transferred to Channel NIC #1 on the Secondary server.

If the Primary and Secondary servers have NICs of the same type in a different order, both the name and IP address of a channel NIC on the Primary server may be transferred to the principal (public) NIC on the Secondary or the name and IP address of the principal (public) NIC may be transferred to a channel NIC. Similarly, the names of the channel NICs may be reversed on the Secondary server under these circumstances. If this happens, it may be difficult to reconcile the names of the NICs with their physical identities, making it hard to assign the correct IP address to each NIC on the Secondary server.

It is part of the normal VMware vCenter Server Heartbeat installation process to manually assign the correct IP addresses to each NIC on the Secondary server. If there is no channel connection between the servers, check that the IP addresses on the Secondary server's channel NICs are correctly configured. Also, double-check the settings for the principal (public) NIC, since any configuration error here may not be apparent until a switchover is performed or a failover occurs.

It is possible to capture the identities of all of the NICs on the Secondary server prior to installing VMware vCenter Server Heartbeat, by opening a Windows Command Prompt on that server and executing the following command:

ipconfig /all > ipconfig.txt

This saves the current name, TCP/IP configuration, and MAC address of each NIC on the Secondary server to a file called ipconfig.txt, which is present on that server after the Plug and Play phase of the VMware vCenter Server Heartbeat install has completed. At this point, it is possible to compare the pre-install and post-install state of each NIC by running ipconfig /all from a Windows command prompt and comparing the output of this command with the content of the file ipconfig.txt. The MAC address of each NIC is tied to the physical identity of each card, and never changes - so it is possible to identify each NIC by its MAC address and determine its original name and network configuration, even if these have been updated by the Plug and Play process.