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NE40E V800R010C10SPC500 Feature Description - IP Services 01

This is NE40E V800R010C10SPC500 Feature Description - IP Services
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Dual-Device ARP Hot Backup

Dual-Device ARP Hot Backup

Background

Figure 2-14 shows a typical network topology with a VRRP backup group deployed. In the topology, Device A is a master device, and Device B is a backup device. In normal circumstances, Device A forwards uplink and downlink traffic. If Device A or the link between Device A and the Switch becomes faulty, a master/backup VRRP switchover is triggered to switch Device B to the Master state. Device B needs to advertise a network segment route to a device on the network side to direct downlink traffic to Device B. If Device B has not learned ARP entries from a device on the user side, the downlink traffic is interrupted.

NOTE:

Dual-device ARP hot backup applies in both Virtual Router Redundancy Protocol (VRRP) and enhanced trunk (E-Trunk) scenarios. This section describes the implementation of dual-device ARP hot backup in VRRP scenarios.

Figure 2-14 VRRP application

Implementation

After you deploy dual-device ARP hot backup, the new master device forwards the downlink traffic without learning ARP entries again. Dual-device ARP hot backup ensures downlink traffic continuity.

As shown in Figure 2-15, a VRRP backup group is configured on Device A and Device B. Device A is a master device, and Device B is a backup device. Device A forwards uplink and downlink traffic.

Figure 2-15 Dual-device ARP hot backup
If Device A or the link between Device A and the Switch becomes faulty, a master/backup VRRP switchover is triggered to switch Device B to the Master state. Device B needs to advertise a network segment route to a device on the network side to direct downlink traffic to Device B.
  • Before you deploy dual-device ARP hot backup, Device B does not learn ARP entries from a device on the user side and therefore a large number of ARP Miss messages are transmitted. As a result, system resources are consumed and downlink traffic is interrupted.
  • After you deploy dual-device ARP hot backup, Device B backs up ARP information on Device A in real time. When Device B receives downlink traffic, it forwards the downlink traffic based on the backup ARP information.

Related Concepts

VRRP is a fault-tolerant protocol. VRRP groups several routers into a virtual router. If the next hop of a router is faulty, VRRP switches traffic to another router for transmission, ensuring the continuity and reliability of communication.

For details about VRRP, see the chapter "VRRP" in the NE40E Feature Description - Network Reliability.

E-Trunk is an inter-device link aggregation mechanism, which aggregates links between devices to provide device-level reliability. For details about E-Trunk, see the chapter "E-Trunk" in the NE40E Feature Description - LAN and MAN Access.

Usage Scenario

Dual-device ARP hot backup applies when VRRP or E-Trunk is deployed to implement a master/backup device switchover.

NOTE:
To ensure that ARP entries are completely backed up, set the VRRP or E-Trunk switchback delay to a value greater than the number of ARP entries that need to be backed up divided by the slowest backup speed.

Benefits

Dual-device ARP hot backup prevents downlink traffic from being interrupted because the backup device does not learn ARP entries of a device on the user side during a master/backup device switchover, which improves network reliability.

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Updated: 2019-01-03

Document ID: EDOC1100055041

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