Course11:Advanced - Standby PBX
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Course11 (this version) | Course12
This book discusses the installation of a standby PBX for enhanced availability.
Setup
As discussed in the basic training, a standby PBX can be set up and will take over the master PBX's role whenever it fails.
The gateway platform used as a standby PBX needs to be able to handle as much registrations and object definition as the the master PBX does. However, it does not need to be the same type of device. E.g. an IP3010 may serve as a standby for an IP6000 in certain scenarios.
To set up the standby correctly, you need to create an almost full replica. This involves
The gateway platform used as a standby PBX needs to be able to handle as much registrations and object definition as the the master PBX does. However, it does not need to be the same type of device. E.g. an IP3010 may serve as a standby for an IP6000 in certain scenarios.
To set up the standby correctly, you need to create an almost full replica. This involves
- PBX Config
- PBX Objects
- Licenses
Config
The settings in the PBX/Config/General and PBX/Config/myPBX need to be copied manually from the Master PBX to the Standby PBX.
Almost all properties from the master PBX general config must be set identically in the standby PBX, except the PBX Mode property which must be set to Standby instead of Master. The remaining settings in the other pages mentioned should be set identical in master and standby. Also, in the standby PBX general settings, there is an additional area Standby PBX. Set the Master property to the IP address of the master PBX. This will be used to register with the master PBX.
When maintaining a PBX installation with standby, make sure you update the standby whenever you change the master's settings!
All other settings underneathPBX/Config are replicated from the master PBX.
Almost all properties from the master PBX general config must be set identically in the standby PBX, except the PBX Mode property which must be set to Standby instead of Master. The remaining settings in the other pages mentioned should be set identical in master and standby. Also, in the standby PBX general settings, there is an additional area Standby PBX. Set the Master property to the IP address of the master PBX. This will be used to register with the master PBX.
When maintaining a PBX installation with standby, make sure you update the standby whenever you change the master's settings!
All other settings underneath
Object Replication
In order to take over the master PBX's role, the standby PBX needs to know all of the PBX objects the master knows. This is done automatically using LDAP replication between master and standby PBX. It is activated by ticking the Replicate from Master check-mark in the PBX/Config/General tab. The current replication state is shown next to the Replicate from Master check-box.
For the replication to succeed, the standby PBX needs to know the master PBX's PBX password and the _KADMIN_ password. You thus need to set both in the PBX/Config/Security tab.
For the replication to succeed, the standby PBX needs to know the master PBX's PBX password and the _KADMIN_ password. You thus need to set both in the PBX/Config/Security tab.
Licenses
To enable standby functionality, a standby license must be present on the standby PBX. This license (called Standby11) must have the same size as the port license installed on the device.
As the standby PBX takes over all duties, it in addition to that needs to have the same licenses (e.g. voicemail-lic, operator-lic) available as the master PBX has.
There are two ways to achieve this.
It is possible to install separate licenses of the same type and with the same amounts on the standby PBX. While this is an option theoretically, there are only rare conditions where it makes sense as the licenses installed on a master cannot be used on the standby (licenses are bound to device MAC addresses). This implies that you would need to purchase a complete copy of the master's licenses.
All relevant licenses can be replicated from the master PBX by virtue of a the PBX Central licensing concept. If no Port license is installed locally on a standby PBX it obtains automatically all PBX licenses from the master.
You will thus install no license on the standby, as it will replicate all licenses (including theStandby#XX license, which is not used by the master PBX) from the master PBX's license store.
As the standby PBX takes over all duties, it in addition to that needs to have the same licenses (e.g. voicemail-lic, operator-lic) available as the master PBX has.
There are two ways to achieve this.
Installing separate Licenses
It is possible to install separate licenses of the same type and with the same amounts on the standby PBX. While this is an option theoretically, there are only rare conditions where it makes sense as the licenses installed on a master cannot be used on the standby (licenses are bound to device MAC addresses). This implies that you would need to purchase a complete copy of the master's licenses.
Replicating Licenses from the Master PBX
All relevant licenses can be replicated from the master PBX by virtue of a the PBX Central licensing concept. If no Port license is installed locally on a standby PBX it obtains automatically all PBX licenses from the master.
You will thus install no license on the standby, as it will replicate all licenses (including theStandby#XX license, which is not used by the master PBX) from the master PBX's license store.
Verification
Once your setup is complete, you can easily verify it.
On the master PBX, you should see an entry called_STANDBY_ in the registration list. Likewise, you will see an entry called _ACTIVE_ on the standby PBX.
If this is not the case, it is usually due to one of these problems:
There should be all expected licenses in the Licenses area of the standby PBX's PBX/Config/General tab.
All objects known to the master PBX should be seen in the standby PBX's users list.
If this is not the case, replication doesn't work properly. Check the standby PBX's replicator state.
Please note that all settings in the PBX/Config/Filter tab are replicated as well!
Once everything looks good and your phones are registered to the master, you should simply turn off the master PBX. This is how the phone screen should look like (observe the symbol in the lower right):
Master / Standby Registrations
On the master PBX, you should see an entry called_STANDBY_ in the registration list. Likewise, you will see an entry called _ACTIVE_ on the standby PBX.
If this is not the case, it is usually due to one of these problems:
- Master property wrong in standby PBX
- PBX password in master and standby differ
Licenses
There should be all expected licenses in the Licenses area of the standby PBX's PBX/Config/General tab.
PBX Objects
All objects known to the master PBX should be seen in the standby PBX's users list.
If this is not the case, replication doesn't work properly. Check the standby PBX's replicator state.
Please note that all settings in the PBX/Config/Filter tab are replicated as well!
Forcing Fail Over
Once everything looks good and your phones are registered to the master, you should simply turn off the master PBX. This is how the phone screen should look like (observe the symbol in the lower right):
good registration
After a minute or so, have look at the registration symbol: it should indicate loss of registration:
lost registration
After accessing the alternate gatekeeper (that is, the standby PBX), the symbol will look again as in the good registration screenshot above.
Only interesting for students working with innovaphone for a longer time, i.e. before version 10(Service Release 3). There was also a specific symbol for the alternate registration, however the display of the alternate registration was removed in the current firmware.
The reason for it was that only in rather simple configurations the primary and the alternate gatekeeper can be clearly distinguished. In more complex PBX redundancy configurations it may be not possible to find out the role of the gatekeeper a phone is registered to. Thus it's better to leave off this information because it's not really important for the average phone user.
After a minute or so, have look at the registration symbol: it should indicate loss of registration:
lost registration
After accessing the alternate gatekeeper (that is, the standby PBX), the symbol will look again as in the good registration screenshot above.
Only interesting for students working with innovaphone for a longer time, i.e. before version 10(Service Release 3). There was also a specific symbol for the alternate registration, however the display of the alternate registration was removed in the current firmware.
The reason for it was that only in rather simple configurations the primary and the alternate gatekeeper can be clearly distinguished. In more complex PBX redundancy configurations it may be not possible to find out the role of the gatekeeper a phone is registered to. Thus it's better to leave off this information because it's not really important for the average phone user.
Setting up the Clients
For the standby scenario to work, it is essential that all affected clients (phones, gateways, etc.) are able to register with both the master PBX and the standby PBX. Apart from the fact that there must be appropriate IP routings, the clients either need to know both PBX's IP addresses or need to be able to find them dynamically. As already discussed in the basic training topic of PBX initial configuration, the fail over process relies on the clients ability to detect loss of the master PBX and subsequent registration with the standby PBX.
The following methods exist to make the PBX's IP addresses known to clients:
Both for H.323 and SIP devices, a dynamic, IP multicast based discovery mechanism is available. This is known as gatekeeper discovery in H.323 and also available in SIP. For innovaphone devices, discovery is enabled when there is no gatekeeper or no SIP domain configured.
This is the recommended method if a PBX is present in the LAN segment of the client as it is most robust and requires no configuration on the client side.
The IP addresses of both the master and the standby PBX can be hard configured into the clients. This is often the only method available for 3rd party devices. When doing so, it is critical to always configure (and test!) both IP address. These are often called primaryand secondary (or alternate) gatekeeper for H.323 devices. For SIP devices, the 2 IP addresses are usually retrieved from the domain name system (DNS) based on the domainprovided.
It is possible to mix both. For example, if the Primary Gatekeeper Address is left empty in thePhone/User/General tab, gatekeeper discovery will be tried first. If this fails and Secondary Gatekeeper Address is non-empty, the IP address specified is tried.
This configuration allows for the use of a PBX and it's standby in the local LAN segment (which both would be found using discovery) and a third PBX somewhere remote specified with an explicit IP address.
This is a slight variation of the hard configuration setup. The PBX IP addresses are provided to the clients by DHCP vendor options. Works for both H.323 and SIP. This is the recommended method when using an innovaphone DHCP server or when there is no PBX local to the clients LAN segment.
The following methods exist to make the PBX's IP addresses known to clients:
Discovery
Both for H.323 and SIP devices, a dynamic, IP multicast based discovery mechanism is available. This is known as gatekeeper discovery in H.323 and also available in SIP. For innovaphone devices, discovery is enabled when there is no gatekeeper or no SIP domain configured.
This is the recommended method if a PBX is present in the LAN segment of the client as it is most robust and requires no configuration on the client side.
Hard Configuration
The IP addresses of both the master and the standby PBX can be hard configured into the clients. This is often the only method available for 3rd party devices. When doing so, it is critical to always configure (and test!) both IP address. These are often called primaryand secondary (or alternate) gatekeeper for H.323 devices. For SIP devices, the 2 IP addresses are usually retrieved from the domain name system (DNS) based on the domainprovided.
Mixed Hard Configuration and Discovery
It is possible to mix both. For example, if the Primary Gatekeeper Address is left empty in the
This configuration allows for the use of a PBX and it's standby in the local LAN segment (which both would be found using discovery) and a third PBX somewhere remote specified with an explicit IP address.
DHCP Vendor Option
This is a slight variation of the hard configuration setup. The PBX IP addresses are provided to the clients by DHCP vendor options. Works for both H.323 and SIP. This is the recommended method when using an innovaphone DHCP server or when there is no PBX local to the clients LAN segment.
Using the Standby as a Gateway
A standby PBX will do nothing as long as it's master PBX is available. However, the gateway the standby PBX runs on will be active even though the standby PBX itself is not. This allows to use the gateway's capabilities (most notably the interfaces) to be used in normal operation.
Assume a scenario where a customer has 2 physical trunk lines and asks for a redundant solution. In this case, the trunk lines can be connected to both gateways. In normal operation, both trunks are available. In the standby case, PRI#2 is still available.
When using gateways with support for looped-in configurations as PBX platforms, a solution can be implemented that makes both trunk lines available when the master PBX fails.
Assume a scenario where a customer has 2 physical trunk lines and asks for a redundant solution. In this case, the trunk lines can be connected to both gateways. In normal operation, both trunks are available. In the standby case, PRI#2 is still available.
When using gateways with support for looped-in configurations as PBX platforms, a solution can be implemented that makes both trunk lines available when the master PBX fails.