我正在遵循Multi-DC Consul on Kubernetes来实现示例。在配置过程中，一切正常。配置完成后，两个数据中心的领事成员如下：
阿姆斯特丹：
Node Address Status Type Build Protocol DC Segment
consul-0 10.20.2.6:8301 alive server 1.2.1 2 ams <all>
consul-1 10.20.0.5:8301 alive server 1.2.1 2 ams <all>
consul-2 10.20.1.11:8301 alive server 1.2.1 2 ams <all>
gke-ams-default-pool-a85b4aae-1gtl 10.154.0.14:8301 alive client 1.2.1 2 ams <default>
gke-ams-default-pool-a85b4aae-kktf 10.154.0.15:8301 alive client 1.2.1 2 ams <default>
gke-ams-default-pool-a85b4aae-m4dj 10.154.0.16:8301 alive client 1.2.1 2 ams <default>
伦敦：
Node Address Status Type Build Protocol DC Segment
consul-0 10.28.1.8:8301 alive server 1.2.1 2 london <all>
consul-1 10.28.0.9:8301 alive server 1.2.1 2 london <all>
consul-2 10.28.2.14:8301 alive server 1.2.1 2 london <all>
gke-london-default-pool-1ea5feef-0t50 10.164.0.22:8301 alive client 1.2.1 2 london <default>
gke-london-default-pool-1ea5feef-329g 10.164.0.21:8301 alive client 1.2.1 2 london <default>
gke-london-default-pool-1ea5feef-z62n 10.164.0.20:8301 alive client 1.2.1 2 london <default>
然后，我尝试从伦敦加入阿姆斯特丹的服务部门并运行consul join -wan 10.20.2.6。一段时间后，我得到了错误
Error joining address '10.20.2.6': Unexpected response code: 500 (1 error(s) occurred:
* Failed to join 10.20.2.6: dial tcp 10.20.2.6:8302: i/o timeout)
Failed to join any nodes.
此错误的可能原因是什么？