Db2 instance start failed with error SQL6048N

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After the IP address change on the machine,  Db2 instance couldn't be brought up. The error received was:

$ db2start
01/01/2018 19:00:00 0 0 SQL6048N A communication error occurred during START or STOP DATABASE MANAGER processing.
SQL1032N No start database manager command was issued. SQLSTATE=57019

The following messages are found in db2diag.log:

2018-01-01-19.00.00.977600-240 I1094433E797          LEVEL: Severe

PID     :1234                 TID : <TID> PROC : db2start

INSTANCE: db2inst1             NODE : 000

HOSTNAME: host2

FUNCTION: DB2 UDB, base sys utilities, sqlePdbStartStopNode, probe:1106

DATA #1 : String, 12 bytes

host is down

DATA #2 : String, 60 bytes

/home/ldapdb2/sqllib/adm/db2rstar db2profile db2star2 SN 0 0

DATA #3 : String, 9 bytes

host2

To diagnose the problem, you can ping itself on the same machine by issuing "ping host2" command:

# ping host2
PING host2 (192.168.157.130) 56(84) bytes of data.
From host (192.168.157.129) icmp_seq=2 Destination Host Unreachable

To resolve the problem, address the above error by correcting the IP address so that it is reachable on the machine,

for instance, verify the IP address is correct in /etc/hosts.

Once the machine is reachable, Db2 instance can be started.