High availability overview

1

Decrease system software and hardware faults

·     Hardware—Simplified circuit design, enhanced production techniques, and reliability tests.

·     Software—Reliability design and test.

2

Protect system functions from being affected if faults occur

Device and link redundancy and switchover.

3

Enable the system to recover as fast as possible

Performing fault detection, diagnosis, isolation, and recovery technologies.

DLDP

DLDP deals with unidirectional links that might occur in a network. When detecting a unidirectional link, DLDP, as configured, can shut down the related port automatically or prompt users to take actions to avoid network problems.

"Configuring DLDP"

Ethernet OAM

As a tool monitoring Layer 2 link status, Ethernet OAM is mainly used to address common link-related issues on the last mile. You can monitor the status of the point-to-point link between two directly connected devices by enabling Ethernet OAM on the two devices.

"Configuring Ethernet OAM"

BFD

BFD provides a single mechanism to quickly detect and monitor the connectivity of links or IP forwarding in networks. To improve network performance, devices must quickly detect communication failures to restore communication through backup paths as soon as possible.

"Configuring BFD"

Monitor Link

Monitor Link associates the state of downlink interfaces with the state of uplink interfaces in a monitor link group. When Monitor Link shuts down the downlink interfaces because of an uplink failure, the downstream device changes connectivity to another link.

"Configuring Monitor Link"

Track

The Track module implements collaboration between different modules. The collaboration involves three sets of modules: application, Track, and detection. These modules collaborate with one another through collaboration entries. The detection modules trigger the application modules to perform certain operations through the Track module. The detection modules probe such items as link status and network performance, and inform the application modules of the detection result through the Track module. Once notified of network status changes, the application modules use the changes to avoid communication interruption and network performance degradation.

"Configuring Track"

Active and standby switchover

When a device has two MPUs installed, one MPU is the active MPU, and the other is the standby MPU. Only the active MPU forwards packets and processes services. Typically the system selects the MPU with a smaller slot number as the active MPU. The standby MPU keeps consistent configurations with those on the active MPU through the synchronization function. When the active MPU fails or is removed, the standby MPU automatically becomes the active MPU to ensure non-stop operating of the devices.

N/A

Ethernet link aggregation

Ethernet link aggregation, or link aggregation, aggregates multiple physical Ethernet links into one logical link to increase link bandwidth beyond the limits of any one single link. This logical link is an aggregate link. It allows for link redundancy because the member physical links can dynamically back up one another.

Layer 2—LAN Switching Configuration Guide

Smart Link

Smart Link provides link redundancy and fast convergence in a dual uplink network, allowing the backup link to take over quickly when the primary link fails.

"Configuring Smart Link"

MSTP

As a Layer 2 management protocol, MSTP eliminates Layer 2 loops by selectively blocking redundant links in a network, and in the meantime, allows for link redundancy.

Layer 2—LAN Switching Configuration Guide

RRPP

RRPP is a link layer protocol designed for Ethernet rings. RRPP can prevent broadcast storms caused by data loops when an Ethernet ring is healthy, and rapidly restore the communication paths between the nodes in the event that a link is disconnected on the ring.

"Configuring RRPP"

GR

GR prevents forwarding discontinuity caused by a protocol restart (including a BGP, IS-IS, OSPF, or LDP) or an active/standby switchover. This feature requires the peer devices to implement routing information backup and recovery.

Related chapters in Layer 3—IP Routing Configuration Guide and MPLS Configuration Guide

VRRP

VRRP is an error-tolerant protocol, which provides highly reliable default links on multicast and broadcast LANs such as Ethernet, avoiding network interruption due to failure of a single link.

"Configuring VRRP"