What is Standby NameNode

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One of two name nodes in HDFS HA framework that is always kept ready to take over the responsibility of Active NameNode if the current active NameNode goes down.

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Precautions for active/standby upgrade in hot standby deployment on the USG2000&5000
Precautions for active/standby upgrade in hot standby deployment on the USG2000&5000 are as follows: As for software version upgrade in hot standby deployment, you shall comply with a primary principle. That is, you shall upgrade the active and standby devices individually and upgrade the standby device first and then the active device. In addition, you must disable the HRP function during the upgrade. Note: For software version upgrade in hot standby deployment, the target software versions of the active and standby devices must be the same. Otherwise, the HRP function may fail to be enabled simultaneously. Hardware restrictions Currently, hot standby can be implemented only between two devices. The active and standby devices must have the same product model and version. The active and standby devices must have the same number and types of boards installed in the same arrangement. Otherwise, the information synchronized from the active device does not match the physical configuration of the standby device. As a result, faults occur after an active/standby switchover. If you want to use a Layer-2 interface as a heartbeat interface, add the Layer-2 interface to a VLAN. Then create a VLANIF interface and configure an IP address for it. Use the VLANIF interface as a heartbeat interface and specify remote to specify the IP address of the heartbeat interface on the remote device. Software restrictions The active and standby devices must use the same software version. Otherwise, configuration commands or session list structures of the different software versions may be different. In this case, errors may occur on the active and standby devices when you back up configuration commands and status. The BootROM versions on the active and standby devices must be the same. The operating mode of the active and standby devices must be the same, that is, both the active and standby devices must be in firewall mode or UTM mode. You are advised to use the initial configuration file on both devices. Otherwise, faults may occur after the active/standby switchover because of configuration conflicts. The names, quantities, and configuration sequence of virtual firewalls on the active and standby devices must be the same. The interfaces on the same slot of the active and standby devices must be added to the same security zone. For example, if the GigabitEthernet0/0/1 interface on the active device is added to the Trust zone, the GigabitEthernet0/0/1 interface on the standby device must also be added to the Trust zone. Configurations of heartbeat interfaces (HRP heartbeat link) on the active and standby devices must be consistent. Note: The USG2110-X/2100 and USG2100 BSR/HSR do not support the function of specifying the heartbeat interface IP address of the peer device. Therefore, you cannot use the VLANIF interface as the heartbeat interface. The service interfaces of the active and standby devices use fixed IP addresses. Therefore, you cannot use the dual-system hot backup function together with functions for obtaining IP address automatically, such as PPPoE dial-up, DHCP client, 3G, and XDSL.

Whether the standby firewall forwards traffic in hot standby deployment
The standby device does not forward service traffic. However, the device properly forwards traffic sent to it, such as the ICMP packet for pinging the device interface IP address. Therefore, you can view traffic on the standby device.

Whether it is normal that the output of the display hrp group command displays that the status of certain groups is disable in hot standby deployment
It is normal. In hot standby deployment, only the active VGMP group on the active device is working, and only the standby VGMP group on the standby device is working.

Concepts of configuring active and standby firewalls
On a load balancing network, to enable both devices to work in master state, consider the following issues: How to back up information between the devices? Which commands need to be backed up? Which is the backup direction? To avoid errors during the backup, the USG introduces the concept of designated active and standby devices. The firewall that sends backup configurations is called the designated active device (whose system name starts with "HRP_M"), and the firewall that receives backup configurations is called the designated standby device (whose system name starts with "HRP_S"). A firewall must meet the following requirements to become the designated active device: In the VRRP group, only the firewalls in master state have the chance to be the designated master device. In load balancing mode, the two hot standby USGs are both master devices. In this case, the designated master device is selected according to the priorities of the VRRP groups and the descending order of the real IP addresses of the heartbeat interfaces. The switchover between designated active and standby devices is not implemented unless a fault occurs on the designated active device or the designated active device quits the VRRP group for the stability of the designated active device.

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