EVPN Multihoming Fast Failover via Remote DF Election
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In Ethernet Virtual Private Network (EVPN) environments with multihoming, network devices face challenges in quickly switching traffic when the active redundant device fails, especially when there are more than two redundant devices, leading to traffic disruption due to the need to purge and relearn forwarding tables.
Innovation Solution
Remote network devices store EVPN type-4 routes for all redundant devices, allowing them to run the Designated Forwarder election algorithm and predict the next active device, enabling quick adjustment of forwarding tables without rejecting foreign ES routes, thus maintaining fast-switch capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If remote network devices reject foreign ES routes (conventional practice), then forwarding table simplicity is maintained, but fast-switch capability is lost when active device fails
Solution Approach 1:
The patent applies preliminary action by having remote network devices store EVPN type-4 routes for all redundant devices in advance, before any failure occurs. This allows the remote device to pre-calculate and predict the next active device using the DF election algorithm, enabling immediate forwarding table updates without purging entries when a failure occurs, thus achieving fast switching while maintaining controlled forwarding table complexity
2Reliability
If more than two redundant network devices are used in single-active configuration, then network redundancy is improved, but fast-switch capability is lost due to inability to predict next active device
Solution Approach 1:
The patent enables fast switching with multiple redundant devices by having the remote network device store EVPN type-4 routes for all redundant devices in advance. When the active device fails, the remote device can immediately run the DF election algorithm using the stored routes to predict which surviving device will become the next active device, avoiding traffic disruption and relearning delays
Solution Approach 2:
The patent implements feedback by having the remote network device continuously monitor EVPN AD route advertisements from redundant devices. When an active device fails and stops advertising, the remote device receives feedback about the failure and uses the stored type-4 routes to predict and switch to the next active device, enabling fast response to failures in multi-device configurations
3Reliability
If forwarding table is purged and relearned after active device failure, then correct forwarding is ensured, but network traffic speed significantly slows down
Solution Approach 1:
The patent applies preliminary action by pre-storing EVPN type-4 routes for all redundant devices and pre-calculating potential next active devices before failures occur. This allows the remote network device to immediately update forwarding tables with the predicted next active device upon failure detection, maintaining forwarding accuracy while avoiding the time-consuming process of purging and relearning forwarding entries, thus preserving network traffic speed
Data Source
AI summary
Techniques described herein provide for fast updating of a forwarding table in a single active multihoming configuration. A first network device that is not connected to an ethernet segment (ES), receives a plurality of ethernet segment (ES) routes (e.g., EVPN type-4 routes) from a plurality of network devices that are connected to a host via the ES. When connectivity is lost to the on a designated forwarded for the ES, t the first network device performed a designated forwarding election algorithm based on the plurality of the received ES routes, to identify that a second network device of the plurality of network devices is designated as a new forwarding device. The first network device modifies an entry in a forwarding table to indicate that the host is now reachable via the second network device.