Stackable Switch Failover Using Secondary IP Addresses
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Solution Overview
Problem
Stackable network switches face issues when the master stack unit cannot communicate with other units due to failures, leading to a network condition where multiple stack units share the same IP address, which is not permitted.
Innovation Solution
Implementing a failover scheme where each stack unit has a primary and a secondary IP address, allowing units to communicate using these 'hidden' addresses when the primary communication fails, and determining which set of units continues to use the original IP address based on predetermined criteria.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If stack units communicate using a single shared IP address through the master stack unit, then network simplicity is improved, but network reliability deteriorates when stacking links fail
Solution Approach 1:
The patent assigns secondary IP addresses to stack units in advance, before any failure occurs. These secondary addresses are kept dormant during normal operation but are immediately activated when stacking link failures are detected, allowing rapid failover without reconfiguration delays
Solution Approach 2:
The system dynamically changes the IP address parameter used by stack units based on the operational state of stacking links. When failures occur, the network transitions from using a single shared IP address through the master unit to using individual secondary IP addresses assigned to each stack unit, resolving the IP conflict while maintaining connectivity
2Reliability
If stack units use unique IP addresses independently, then network reliability is improved during failures, but device complexity increases
Solution Approach 1:
The secondary IP addresses serve multiple functions: they act as backup communication addresses during failures, enable direct peer-to-peer communication between stack units, and provide a mechanism for failure detection. This multi-functionality avoids the need for separate monitoring systems while improving reliability
3Ease of operation
If the master stack unit maintains control for all stack units, then ease of operation is improved, but reliability deteriorates when the master unit fails
Solution Approach 1:
The system pre-configures secondary IP addresses and communication paths for all stack units before failures occur. When the master unit fails, these pre-established paths enable immediate autonomous operation of backup units without requiring complex real-time reconfiguration or election protocols
Solution Approach 2:
The patent segments the control function by enabling individual stack units to operate autonomously with their own secondary IP addresses when isolated from the master unit. This segmentation allows the network to function as multiple independent units rather than a single failed entity, improving system availability
Data Source
AI summary
A method, apparatus, and computer-readable media for a stackable multi-layer switch comprises a first set of stack units comprising a master stack unit, wherein one of the stack units in the first set comprises a first port to communicate with a network using a first Internet Protocol address; and a second set of the stack units comprising a backup master stack unit, wherein one of the stack units in the second set comprises a second port to communicate with the network using the first Internet Protocol address; wherein each of the stack units comprises a control plane processor, one or more ports, a stacking interface, and a forwarding engine to communicate with the control plane processor, the ports, and the stacking interface; wherein the stack units communicate with each other through the stacking interfaces; and wherein, when the master stack unit is unable to communicate with the backup master stack unit through the stacking interfaces, the first and second ports attempt to communicate with each other over the network using a second Internet Protocol address associated with the first port and a third Internet Protocol address associated with the second port.