sudo vi /etc/inetd.conf并加入以下一行 
telnet stream tcp nowait telnetd /usr/sbin/tcpd /usr/sbin/in.telnetd

# Simple configuration file for xinetd 
# 
# Some defaults, and include /etc/xinetd.d/ 

defaults 
{ 

# Please note that you need a log_type line to be able to use log_on_success 
# and log_on_failure. The default is the following : 
# log_type = SYSLOG daemon info 


instances = 60 
log_type = SYSLOG authpriv 
log_on_success = HOST PID 
log_on_failure = HOST 
cps = 25 30 
} 


includedir /etc/xinetd.d

# default: on 
# description: The telnet server serves telnet sessions; it uses \ 
# unencrypted username/password pairs for authentication. 
service telnet 
{ 
disable = no 
flags = REUSE 
socket_type = stream 
wait = no 
user = root 
server = /usr/sbin/in.telnetd 
log_on_failure += USERID 
}

service telnet 
{ 
disable =no 
bind =192.168.1.2 
only_from=192.168.1.0/24 
#上面这两行说明仅提供内部网段！ 
Instance =UNLIMITED 
Nice =0 
Flags =REUSE 
socket_type=stream 
wait =no 
user =root 
#server =/usr/sbin/telnetd 
server =/usr/sbin/in.telnetd 
server_args =-a none 
log_on_failure +=USERID 
} 

service telnet 
{ 
disable =no 
bind =140.116.142.196 
only_from=140.116.0.0/16 
no_access=140.116.32.{10,26} 
#上面三行设置外部较为严格的限制 
instance =10 
umask =022 
nice =10 
flags =REUSE 
socket_type=stream 
wait =no 
user =root 
#server =/usr/sbin/telnetd 
server =/usr/sbin/in.telnetd 
log_on_failure +=USERID 
}

/sbin/iptables -A INPUT -p tcp -i eth0 -s 192.168.0.0/24 --dport 23 -j ACCEPT 
/sbin/iptables -A INPUT -p tcp -i eth0 -s 61.xxx.xxx.xxx --dport 23 -j ACCEPT 
/sbin/iptables -A INPUT -p tcp -i eth0 --dport 23 -j DROP

vi /etc/hosts.allow 
in.telnetd:192.168.0.1,192.168.0.2,192.168.0.3,192.168.0.4,192.168.0.5:allow