Connection refused when connecting to consul agent in client mode

I’m running this setup from Hashi
This setup runs a 3 node consul agent server cluster and one node consul agent client.
consul members o/p

Node                  Address          Status  Type    Build   Protocol  DC   Partition  Segment
consul-server1        172.25.0.3:8301  alive   server  1.10.0  2         dc1  default    <all>
consul-server2        172.25.0.5:8301  alive   server  1.10.0  2         dc1  default    <all>
consul-server3        172.25.0.4:8301  alive   server  1.10.0  2         dc1  default    <all>
consul-server-client  172.25.0.2:8301  alive   client  1.10.0  2         dc1  default    <default>

Running a springboot application and using following setup to auto register my service with consul agent client node and I’m getting connection refused errors.
My app configuration as follows

spring:
  cloud:
    consul:
      host: consul-server-client
      port: 8500

Switching configuration to use consul agent server node works fine.

spring:
  config:
    activate:
      on-profile: docker
  cloud:
    consul:
      host: consul-server1
      port: 8500

What’s the purpose of Consul Agent running in a client mode? Am I using Consul Agent Client incorrectly to self register my springboot service ?