In recent years, many studies have proposed using consensus mechanisms to enhance network layer security. However, existing consensus mechanisms have limitations, such as heavy key maintenance, inflexible trust expansion, and high authentication overhead. To address these issues, this study proposes a lightweight consensus framework based on source address validation. The framework optimizes consensus efficiency at multiple levels: First, among consensus nodes within the same domain, the framework uses authentic IP addresses as identities and achieves key aggregation by sharing the same key among nodes within the domain, thus efficiently reducing the number of keys that need to be maintained. Second, at the domain level, the framework constructs a trusted network alliance based on trust derived from authentic IP addresses and aggregates trusted domains through a prefix tree, thus further reducing the number of keys to maintain while enabling flexible trust expansion. Finally, at the node level, to address the issue of high authentication overhead, the framework designs a two-step authentication mechanism based on authentic IP addresses and symmetric keys, effectively reducing overhead and enabling a lightweight consensus process. Simulation experiment results show that the proposed framework can improve consensus throughput by 70% and reduce consensus latency by 40% on average, compared to the consensus mechanism based on ECDSA authentication, significantly improving consensus efficiency.