The network configuration and operating procedures depend on whether IP addresses are inherited after a system switchover. For the applicable procedures, refer to the following subsections:
This subsection explains differences between network configurations.
- Guidelines
- We recommend that you use a system configuration that essentially inherits IP addresses (a multi-standby configuration can be applied only to a system configuration in which IP addresses are inherited). If the system configuration does not inherit the IP addresses, operation is more difficult than when the IP addresses are inherited.
- Some cluster software products inherit IP addresses after a system switchover, and other cluster software products do not. For details, see the documentation for each cluster software product.
- Use of alias IP addresses is recommended.
- Organization of this subsection
- (1) When IP addresses are inherited
- (2) When IP addresses are not inherited
IP addresses can be inherited using either of the following two methods:
- Switching the IP address
- Switching LAN adapters
To switch the IP address, use an alias IP address (that is, stop one IP address and then start the other). In this way, you use the same IP address and host name for the primary system and the secondary system. The following figure shows a network configuration example of inheriting IP addresses (switching the IP address).
Figure 26-25 Network configuration example when IP addresses are inherited (switching the IP address)
![[Figure]](FIGURE/ZU250100.GIF)
To switch LAN adapters, prepare a maintenance LAN adapter in addition to the LAN adapter that HiRDB uses, and you switch the LAN adapter that is being used (that is, stop one LAN adapter and then start the other). In this way, you use the same IP address and host name for the primary system and the secondary system. The following figure shows a network configuration example of inheriting IP addresses (switching LAN adapters).
Figure 26-26 Network configuration example when IP addresses are inherited (switching LAN adapters)
![[Figure]](FIGURE/ZU250110.GIF)
When IP addresses are not inherited, different IP addresses and host names are used for the primary and secondary systems. This means that the host name for the secondary system must be specified in the pdunit -c operand in the HiRDB system common definition.
The following figure shows an example of a network configuration when IP addresses are not inherited.
Figure 26-27 Example of a network configuration when IP addresses are not inherited
![[Figure]](FIGURE/ZU250120.GIF)
- Notes
- For a HiRDB single server configuration, specify the host names of the primary system and the secondary system in the PDHOST operand of the client environment definition.
- When a unit in the system manager does not inherit IP addresses after a system switchover, specify the host names of the primary system and secondary system in the PDHOST operand of the client environment definition. When a unit in the front-end server does not inherit IP addresses after a system switchover, specify the host names of the primary system and secondary system in the PDFESHOST operand of the client environment definition. If you specify the host names in this manner, you do not need to change the value specified in the PDHOST or PDFESHOST operand, even after a system switchover occurs.
- If the running system switches from the primary system to the secondary system when the host names of the primary system and secondary system are specified in the PDHOST operand, UAPs first attempt to connect to the primary system (which is now the standby system). After this attempt fails, the UAPs establish a connection to the secondary system (the current running system), which increases the UAP processing time by the amount of time it takes to establish this new connection. To resolve this problem, set the host name for the client connections to an alias IP address and make sure that IP addresses are inherited. For details about specifying host names in these cases, see 26.2.3 Handling of host names depending on whether IP addresses are inherited.
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