EVPN Reachability Advertising Based on Spanning Tree Forwarding State
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Solution Overview
Problem
Network devices implementing Ethernet Virtual Private Networks (EVPN) and spanning tree protocols experience unintended traffic blackholing due to advertising network reachability based on the apparent up state of Ethernet interfaces, despite the interfaces being in a non-forwarding state according to the spanning tree protocol.
Innovation Solution
Network devices are configured to advertise network reachability information based on logical topology interface states, specifically spanning tree interface states, rather than relying solely on the Ethernet interface and link states, thereby delaying advertisements until the spanning tree interface state transitions to a forwarding state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If network devices advertise network reachability based on Ethernet interface up state, then network reachability information is advertised promptly, but unintended traffic blackholing occurs when interfaces are in non-forwarding state
Solution Approach 1:
The patent applies preliminary action by checking the spanning tree interface state before advertising network reachability information. The device determines whether the interface is in a forwarding state prior to generating EVPN route advertisements, ensuring that reachability is only advertised when the interface is actually ready to forward traffic. This prevents the blackholing problem while maintaining prompt advertisement when conditions are favorable.
2Reliability
If network devices wait for spanning tree forwarding state before advertising reachability, then traffic blackholing is prevented, but network convergence time increases
Solution Approach 1:
The patent implements feedback by continuously monitoring spanning tree interface state changes and dynamically adjusting EVPN route advertisement behavior. When the interface transitions to a forwarding state, the device immediately generates and advertises EVPN routes. When the interface transitions to a non-forwarding state, the device withdraws previously advertised routes. This feedback mechanism ensures reliable traffic forwarding while minimizing convergence delays through responsive state changes.
Data Source
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AI summary
A network device may include memory circuitry and processing circuitry. The processing circuitry may be configured to obtain a spanning tree topology indicating at least one spanning tree interface state. The processing circuitry may be configured to perform reachability information advertisement based on the spanning tree interface state. In some illustrative configurations, the network device may be one of multiple multihoming network devices configured to provide an Ethernet segment and the reachability information being advertised based on the spanning tree interface state includes Ethernet Virtual Private Network (EVPN) route information.