sentinel dashoboard 只能发现springcloud gateway的服务实例，下游的服务不能实现与sentinel dashboard的通信

```
springcloud gateway 相关配置

相关jar包版本

org.springframework.cloud
spring-cloud-starter-gateway
3.0.2

com.alibaba.cloud
spring-cloud-starter-alibaba-nacos-discovery
2020.0.RC1

com.alibaba.cloud
spring-cloud-starter-alibaba-nacos-config
2020.0.RC1

com.alibaba.cloud
spring-cloud-alibaba-sentinel-gateway
2020.0.RC1


com.alibaba.cloud
spring-cloud-starter-alibaba-sentinel
2020.0.RC1

com.alibaba.csp
sentinel-datasource-nacos
1.8.0

配置信息
spring:
cloud:
sentinel:
transport:
dashboard: localhost:8920
scg:
fallback:
response-status: 426
response-body: "{'code':'426' , 'message':'请求频繁，请稍后重试'}"
filter:
enabled: false
datasource:
# 名称随意
flow:
nacos:
server-addr: ${spring.cloud.nacos.discovery.server-addr}
dataId: ${spring.application.name}-gateway-flow
groupId: DEFAULT_GROUP
# 规则类型，取值见：
# com.alibaba.cloud.sentinel.datasource.RuleType
rule-type: gw-flow
api:
nacos:
server-addr: ${spring.cloud.nacos.discovery.server-addr}
dataId: ${spring.application.name}-gateway-api
groupId: DEFAULT_GROUP
# 规则类型，取值见：
# com.alibaba.cloud.sentinel.datasource.RuleType
rule-type: gw-api-group
```

```
下游服务相关jar包版本

com.alibaba.csp
sentinel-datasource-nacos
1.8.1

com.alibaba.cloud
spring-cloud-starter-alibaba-sentinel
2020.0.RC1

下游服务配置信息

spring:
application:
name: jurisdiction-center
cloud:
nacos:
discovery:
server-addr: 120.55.164.146:8848
config:
server-addr: ${spring.cloud.nacos.discovery.server-addr}
file-extension: properties
sentinel:
transport:
dashboard: localhost:8920
enabled: true
datasource:
flow:
nacos:
server-addr: ${spring.cloud.nacos.discovery.server-addr}
data-id: ${spring.application.name}-flow-rules
group-id: SENTINEL_GROUP
data-type: json
rule-type: flow
degrade:
nacos:
server-addr: ${spring.cloud.nacos.discovery.server-addr}
data-id: ${spring.application.name}-degrade-rules
group-id: DEFAULT_GROUP
data-type: json
rule-type: degrade
```

The issue provides Spring Cloud Gateway, Nacos, and Sentinel configuration but names no repository file or test. Start by reproducing the setup with the supplied gateway and downstream-service configurations, then trace dashboard communication for both service types. Done means downstream service instances are also visible and able to communicate with the Sentinel dashboard.

Written by the indexing model from the issue text.