Redundancy with Failover option
Last updated
Last updated
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CAUTION
Configurations from the scenarios below are examples that demonstrate the potential capabilities of the Astra Wireless devices. The configurations may vary depending on the model and firmware version. We do not recommend copying this solutions to the hardware without checking.
Evolution family units have a functional channels redundancy function. A hot reserve might be created by using the Failover option. The Failover option does not depend on the method of data transmission on the main link. The only condition is connectivity at level 2 between Astra Wireless devices through both links. The principle of operation is extremely simple. The Astra Wireless device, on which the Failover option is configured, checks the availability of a specific MAC address through the primary link. If this MAC address is available, then the operation of the backup link is blocked. The radio module stops broadcasting on the backup master. The reserved slave device only listens to the radio while there is no signal from the master. Thus, the backup link can operate on the same frequency as the main one, but it does not have any influence on it. As soon as the tracked MAC address disappears in the main link, the backup link will be unlocked and traffic will begin to be transmitted over it. The process is completely automatic. However, the transition to a backup link is associated with a short-term idle time. Traffic will return automatically to the primary link as soon as backup link is failure. For example, in the figure below, if the Master 1 - Slave 1 link is selected as the main one, the Master 2 device will turn off the radio interface, and the Slave 2 device will switch to the broadcast listening mode.
The tracked MAC address can be determined in two ways: automatically and manually. In the figure below, regardless of the selected method, the Master 1 will track the Slave 1 MAC address and the Master 2 - Slave 2 MAC address.
If Evolution devices are used as the main link, this gives additional advantages. In this case, both radio links can be configured with the Failover option. For both links, the quality of the established connection will be automatically evaluated. Connection with the worst indicators will automatically become a backup link. Channel selection parameters can be controlled manually.
NOTE
It is also possible to connect two Astra Wireless devices to one external antenna or use one radio frequency.
The Failover option is a part of the MINT proprietary protocol, so the task implementation will require joining all devices into a single MINT area. After joining devices into a single MINT area, there is a risk of a switching loop appearance. In this article, we will review two ways to prevent the switching loop appearance:
Using different switch groups (figure 2a): different switch groups are used for data transmission on the main and backup links, on the Master 1-Slave 1 link switch group #1 is used, on the Master 2 - Slave 2 link switch group #2 is used.
Using the switch border option (figure 2b): the switch border option must be enabled on all prf interfaces. At the same time, it is allowed to use the same switch groups for data transmission on the main and backup links.
mint IFNAME failover MAC
Enable Failover option to check "MAC" availability
mint IFNAME failover auto
Enable Failover option to check "MAC" availability. "MAC" will be selected in automatic mode
mint IFNAME [-]failover
Disable Failover
A management is VLAN 100 inside a switch group #100. A transport of user data is inside a switch group #1.
CAUTION
STP protocol may block correct working Failover option, so it should be disabled. Failover option causes short-time loops in one broadcast domain.
If the devices of the main and backup links are mounted on the same site and use the same frequency channel, we recommend to use different "Network SID". This will avoid establishing cross links: Master 1 - Slave 2 and Master 2 - Slave 1. In this example, the Network SIDs 10101010 and 10101011 are used.
The article provides one of the possible configurations of radio link settings and data transmission. The configuration used in your network may differ from the one shown.
Master 1
Slave 1
Master 2
Slave 2
Master 1
Slave 1
Master 2
Slave 2
Use different switch groups (figure 2a):
Master 1
Slave 1
Master 2
Slave 2
Use switch border option (figure 2b):
Master 1
Slave 1
Master 2
Slave 2
Manual MAC address settings:
Master 1
Master 2
Automatic MAC address settings:
Master 1
Master 2
CAUTION
When Failover option is enabled on two devices of the Evolution family, a situation may occur when both links are equal in their characteristics (link cost). In this case, you need to manually specify which of the links will be redundant, assigning an additional cost to a specific interface.
Master 2
Slave 2
