“telnet: Unable to connect to remote host: No route to host” in RHEL

Problem:

I was getting the error “telnet: Unable to connect to remote host: No route to host” in RHEL 6.8 while trying to telnet the port numbers 111 and 2049 (these ports being used for NFS) from a machine to another machine 174.11.1.11 which was NFS server. Policies were already applied on the external firewall for communication between these two servers on these ports.

[root@TestServer root]# telnet 174.11.1.11 111
Trying 174.11.1.11...
telnet: connect to address 174.11.1.11: No route to host
telnet: Unable to connect to remote host: No route to host

Reason:

When it was diagnosed then I found that an internal firewall was enabled on the machine 174.11.1.11 that’s why I was not able to telnet the required ports.

Solution:

Add the two lines shown below in the file /etc/sysconfig/iptables to accept the request comping on these ports 111 and 2049.

[root@TestServer ~]# vi /etc/sysconfig/iptables
..
..
..

-A INPUT -p tcp -m state --state NEW -m tcp --dport 2049 -j ACCEPT
-A INPUT -p tcp -m state --state NEW -m tcp --dport 111 -j ACCEPT

..
..
..

After updating the /etc/sysconfig/iptables file restart the iptables service to enable the policies on the internal firewall.

[root@TestServer ~]# service iptables restart
iptables: Setting chains to policy ACCEPT: filter          [  OK  ]
iptables: Flushing firewall rules:                         [  OK  ]
iptables: Unloading modules:                               [  OK  ]
iptables: Applying firewall rules:                         [  OK  ]

Check the policies by using the command iptables -L

[root@TestServer ~]# iptables -L
Chain INPUT (policy ACCEPT)
target     prot opt source               destination
ACCEPT     all  --  anywhere             anywhere            state RELATED,ESTABLISHED
ACCEPT     icmp --  anywhere             anywhere
ACCEPT     all  --  anywhere             anywhere
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:ssh
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:krb524
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:personal-agent
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:nfs
ACCEPT     udp  --  anywhere             anywhere            state NEW udp dpt:nfs

Now check the required ports 111 and 2049 and you will be able to telnet these ports successfully.

[root@TestServer ~]# telnet 174.11.1.11 2049
Trying 174.11.1.11...
Connected to 174.11.1.11.
Escape character is '^]'.
^]
telnet> quit
Connection closed.


[root@TestServer ~]# telnet 174.11.1.11 111
Trying 174.11.1.11...
Connected to 174.11.1.11.
Escape character is '^]'.
^]
telnet> quit
Connection closed.