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CX11x, CX31x, CX710 (Earlier Than V6.03), and CX91x Series Switch Modules V100R001C10 Configuration Guide 12

The documents describe the configuration of various services supported by the CX11x&CX31x&CX91x series switch modules The description covers configuration examples and function configurations.
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Huawei uses machine translation combined with human proofreading to translate this document to different languages in order to help you better understand the content of this document. Note: Even the most advanced machine translation cannot match the quality of professional translators. Huawei shall not bear any responsibility for translation accuracy and it is recommended that you refer to the English document (a link for which has been provided).
Applicable Scenarios

Applicable Scenarios

This section describes the applicable scenarios of VRRP.

Association Between a VRRP Group and the Interface Status to Monitor the Uplink Interface

A VRRP group can only detect the status change of the interface on which the VRRP group is configured. VRRP cannot detect faults on the uplink interface or direct uplink of the master, so services are interrupted. You can associate a VRRP group with the interface status. When the uplink interface or direct uplink of the master fails, the priority of the master is adjusted. This triggers an active/standby switchover and ensures proper traffic forwarding.

NOTE:
A VRRP group can monitor the interface status in Increased or Reduced mode:
  • In Increased mode, when the monitored interface becomes Down, the priority of the master increases.
  • In Reduced mode, when the monitored interface becomes Down, the priority of the master decreases.
Figure 11-36 Association between a VRRP group and the interface status

As shown in Figure 11-36, a VRRP group is configured between Switch ModuleA and Switch ModuleB. Switch ModuleA is the master and Switch ModuleB is the backup. Switch ModuleA and Switch ModuleB work in preemption mode. On Switch ModuleA, the Reduced mode is used to monitor uplink interface Interface1. When Interface1 becomes faulty, the priority of Switch ModuleA decreases. Then Switch ModuleB becomes the master through negotiation so that user traffic is forwarded correctly.

Association Between VRRP and BFD/NQA/Routing to Monitor the Uplink

VRRP can detect only faults in VRRP groups. Association between a VRRP group and the interface status allows the device to detect faults on the uplink interface or direct uplink of the master. When an indirect uplink of the master fails, VRRP cannot detect the fault, causing user traffic loss. You can configure association between VRRP and BFD/NQA/routing to solve this problem. Association between VRRP and BFD/NQA/routing allows the device to detect faults on the uplink of the master. When the uplink of the master fails, BFD/NQA/routing rapidly detects the fault and notifies the master of adjusting its priority. This triggers an active/standby switchover and ensures proper traffic forwarding.

Figure 11-37 Association between VRRP and BFD/NQA/routing

As shown in Figure 11-37, a VRRP group is configured between Switch ModuleA and Switch ModuleB. Switch ModuleA is the master and Switch ModuleB is the backup. Switch ModuleA and Switch ModuleB work in preemption mode. BFD/NQA/routing is configured to detect faults on the link from Switch ModuleA to Switch ModuleE, and association between VRRP and BFD/NQA/routing is configured on Switch ModuleA. When BFD/NQA/routing detects the fault on the link from Switch ModuleA to Switch ModuleE, BFD/NQA/routing notifies the master of adjusting its priority. Switch ModuleB becomes the master through negotiation so that user traffic is forwarded correctly.

Association Between VRRP and BFD to Implement a Rapid Active/Standby Switchover

A VRRP group sends and receives VRRP Advertisement packets to determine the master and backup statuses. When a VRRP group is faulty, the backup with the highest priority detects the fault and switches to the master after the Master_Down_Interval timer expires. The switchover period is at least 3s. During the switchover period, service traffic is still sent to the original master, causing user traffic loss. Association between VRRP and BFD prevents traffic loss. After a BFD session is configured between the master and the backup, and the BFD session is bound to the VRRP group, the BFD session detects connectivity of the VRRP group. After detecting a fault, the BFD session notifies the VRRP group of an active/standby switchover. This mechanism implements millisecond-level switchover and reduces traffic loss.

Table 11-14 describes the association between the VRRP group and BFD session.

Table 11-14 VRRP and BFD association modes

Association Mode

BFD Session Type

Usage Scenario

VRRP Status Change

BFD Support

Association between a VRRP group and a common BFD session

Static BFD session or static BFD session with automatically negotiated discriminators

A backup monitors the status of the master in a VRRP group. A common BFD session monitors the link between the master and backup.

If the BFD session detects a fault and goes Down, the BFD module notifies the VRRP group of the status change. After receiving the notification, the VRRP group changes VRRP priorities of devices and determines whether to perform an active/standby switchover.

The VRRP-enabled device must be enabled with BFD.

Association between a VRRP group and a link/peer BFD session

Static BFD session or static BFD session with automatically negotiated discriminators

The master and backup monitor the link/peer BFD session. A link BFD session is established between the master and backup. A peer BFD session is established between a downstream switch and each VRRP device. The BFD module helps the VRRP group detect faults on a link between a VRRP-enabled device and the downstream switch.

If the link/peer BFD session detects a fault and goes Down, the BFD module notifies the VRRP group of the status change. After receiving the notification, the VRRP group rapidly performs an active/standby switchover.

The VRRP-enabled device and downstream switch must be enabled with BFD.

Association between a VRRP group and a VRID-based dynamic BFD session

VRID-based dynamic BFD session

A backup monitors the status of the master in a VRRP group. A VRID-based dynamic BFD session is used to monitor the link between the master and backup.

If the VRID-based dynamic BFD session goes Down, BFD notifies the VRRP group of the fault. After receiving the notification, the VRRP group immediately performs an active/standby switchover without changing the VRRP priorities.

The VRRP-enabled device must support BFD.

Figure 11-38 Association between a VRRP group and a common BFD session

As shown in Figure 11-38, a VRRP group is configured between Switch ModuleA and Switch ModuleB. Switch ModuleA is the master and Switch ModuleB is the backup. User traffic is forwarded through Switch ModuleA. Delayed preemption is configured on Switch ModuleA and immediate preemption is configured on Switch ModuleB. BFD sessions are configured on Switch ModuleA and Switch ModuleB and association between VRRP and BFD is configured on Switch ModuleB.

When a fault occurs in the VRRP group, BFD rapidly detects the fault and notifies Switch ModuleB of increasing the priority. In this case, Switch ModuleB has a higher priority than Switch ModuleA. Switch ModuleB becomes the master and forwards user traffic. This implements a rapid active/standby switchover.

Figure 11-39 Association between a VRRP group and a link/peer BFD session

As shown in Figure 11-39, a VRRP group is configured between Switch ModuleA and Switch ModuleB. Switch ModuleA is the master and Switch ModuleB is the backup. User traffic is forwarded through Switch ModuleA. Delayed preemption is configured on Switch ModuleA and immediate preemption is configured on Switch ModuleB. A peer BFD session is established between Switch ModuleA and Switch ModuleB. Link1 BFD session is established between the switch and Switch ModuleA. Link2 BFD session is established between the switch and Switch ModuleB. Association between VRRP and BFD is configured on Switch ModuleB.

When a fault occurs in the VRRP group, Link1 BFD session and the peer BFD session go Down. Link2 BFD session is Up. RouterA's VRRP status directly becomes Initialize. Switch ModuleB's VRRP status directly becomes Master and user traffic is forwarded through Switch ModuleB. This implements a rapid active/standby switchover.

Figure 11-40 Association between a VRRP group and a VRID-based dynamic BFD session

As shown in Figure 11-40, a VRRP group is configured between Switch ModuleA and Switch ModuleB. Switch ModuleA is the master and Switch ModuleB is the backup. User traffic is forwarded through Switch ModuleA. Delayed preemption is configured on Switch ModuleA and immediate preemption is configured on Switch ModuleB. A VRRP group is configured on Switch ModuleA and Switch ModuleB to monitor the VRID-based dynamic BFD session.

If BFD detects a fault, the VRID-based dynamic BFD session goes Down. After receiving the session Down event, Switch ModuleB immediately switches to the master and sends gratuitous ARP packets to update MAC address entries on the switch.

Association Between a VRRP Group and a Direct Route

In a data center, to improve transmission reliability, a server exchanges data with core devices using a VRRP group. To ensure security, the VRRP group of core servers often connects to firewalls. Traffic from servers to core devices is forwarded through the master, and traffic from core devices to servers is forwarded using a routing protocol. In this case, uplink and downlink traffic may be transmitted along different paths. The firewall supports session data synchronization and allows uplink and downlink traffic to be transmitted along different paths. However, this function affects transmission performance. In practice, the firewall has session data synchronization disabled. The firewall may block downlink traffic, causing traffic loss. To solve the problem, associate the VRRP group with the direct route.

Association between the VRRP group and the direct route allows the cost of the direct route to be adjusted based on the VRRP group status. Then the direct route is imported to a dynamic routing protocol for route selection. The route with a smaller cost is preferred by a routing protocol.

As shown in Figure 11-41, association between a VRRP group and a direct route is configured on the interfaces of SwitchA and SwitchB where the VRRP group is configured.
  • When SwitchA is in Master state, the cost of the direct route is 0 (default value). The interface configured with the VRRP group is located on the network segment that this direct route belongs to.

  • When SwitchB is in Backup state, the cost of the direct route can be configured.

Because the route cost on SwitchA is smaller, this route is selected. Uplink and downlink traffic are transmitted along the same path.
Figure 11-41 Association between the VRRP group and the direct route
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Updated: 2019-08-09

Document ID: EDOC1000041694

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