DHCP中的unknown-client问题

hellowangyi

在配置DHCP的dhcpd.conf文件时遇到下面一个问题：
这是rh的一个例子
:confused:
subnet 10.0.0.0 netmask 255.255.255.0 {
  option routers 10.0.0.254;

  # Unknown clients get this pool.
  pool {
    option domain-name-servers bogus.example.com;
    max-lease-time 300;
    range 10.0.0.200 10.0.0.253;
    allow unknown-clients;
  }

  # Known clients get this pool.
  pool {
    option domain-name-servers ns1.example.com, ns2.example.com;
    max-lease-time 28800;
    range 10.0.0.5 10.0.0.199;
    deny unknown-clients;
  }
}

想请教一下：
unknown-clients指的是哪些用户？
known-clients又指的是哪些用户？