Why system is not accessible on the network and a connection attempt fails with "No route to host" ?

Issue

• The system in question cannot ping/ssh any other system an vice versa in same network.
• ping fails as below:

# ping 10.102.X.X
PING 10.102.X.X (10.102.X.X) 56(84) bytes of data.
From 10.102.Y.Y: icmp_seq=2 Destination Host Unreachable
From 10.102.Y.Y icmp_seq=2 Destination Host Unreachable
From 10.102.Y.Y icmp_seq=3 Destination Host Unreachable
From 10.102.Y.Y icmp_seq=4 Destination Host Unreachable

--- HOSTNAME ping statistics ---
11 packets transmitted, 0 received, +3 errors, 100% packet loss, time 10999ms
, pipe 3
#

• ssh fails as below.

# ssh -vvv 10.102.X.X
OpenSSH_5.6p1 (CentrifyDC build 4.5.0-440) (CentrifyDC build 4.5.0-440), OpenSSL 0.9.8k (CentrifyDC build 4.5.0-440) 25 Mar 2009
debug1: Reading configuration data /etc/centrifydc/ssh/ssh_config
debug1: Applying options for *
debug2: ssh_connect: needpriv 0
debug1: Connecting to 10.102.X.X [10.102.X.X] port 22.
debug1: connect to address 10.102.X.X port 22: No route to host
ssh: connect to host 10.102.X.X port 22: No route to host
#

• Same is the situation when trying to access any other system from this system.