Scenario:
We have tow exchange 2010 servers with HAG. When one is offline, the another one will take all the server roles automatically.
But we do not have network load balancer.
We setup mail.xxxxx.com always point to xxmail01 IP address 192.168.x.25 in our LAN. We also setup mail.xxxxx.com alwasy point to xxmail01 NAT public IP address 208.1.x.25.
If xxmail01 offline, we have to change DNS mail.xxxxx.com record point to xxmail01 IP address ( LAN IP 192.168.x.35, WAN IP 208.1.x.35) manually.
But we do not have network load balancer.
We setup mail.xxxxx.com always point to xxmail01 IP address 192.168.x.25 in our LAN. We also setup mail.xxxxx.com alwasy point to xxmail01 NAT public IP address 208.1.x.25.
If xxmail01 offline, we have to change DNS mail.xxxxx.com record point to xxmail01 IP address ( LAN IP 192.168.x.35, WAN IP 208.1.x.35) manually.
The LAN DNS server is intDNS01, WAN DNS server is extDNS01.
Setup Schedule Task on Both DNS servers to run the command line to update DNS A records, if exchange server is offline. After run the cmd scritps successfully, delete them each time.
The DNS update command file store on share folder \\intDNS01\taskscript\updateintdns.bat
The DNS update command file store on share folder \\intDNS01\taskscript\updateintdns.bat
\\extDNS01\taskscript\updateextdns.bat.
Prepare
List the monitor Hosts in file name testRecordList.txt like the following format.
#please the test informantion
#If have internal and external DNS Servers, one record point to one internal and one external IP, please use the following format.
#Int_dns_servername,Ext_dns_servername;full_test_DNS_name;First_Int_IP_Address,Frist_Ext_IP_Address;Second_Int_IP_Address,Second_Ext_IP_Address
intDNS01,extDNS01;mail.xxxxx.com;192.168.x.25,208.1.x.25;192.168.x.35,208.1.x.35
#If one has internal DNS Servers, please use the following format.
#Int_dns_servername;full_test_DNS_name;First_Int_IP_Address;Second_Int_IP_Address
Python Script
File Name: gendnsupdatecmd.py
'''
Created on Jan 10, 2013
@author: chu
'''
import os, time
#Run nslookup to check if the A Record is list on the DNS server or not.
def getARecordIp(aName):
os.popen("ipconfig /flushdns")
nslookupcmd = "nslookup " + aName
nslookupReturn = os.popen(nslookupcmd).readlines()
if len(nslookupReturn) < 4:
return "Failed"
elif aName in nslookupReturn[3]:
return nslookupReturn[4].split(' ')[2:]
else:
return "Failed"
#Run Ping to check the A Record Host is alive or not.
def pingTest(ip):
pingcmd = "ping -n 1 -i 5 " + ip
testResult = os.popen(pingcmd).readlines()
if len(testResult) < 2:
result = False
return result
if 'Request timed out.' in testResult[3]:
result = False
return result
else:
result = True
return result
#Generate delete A Record command line.
def delRecord(record,intip):
intdelRecordcmd = ''
extdelRecordcmd = ''
for i in range(2,len(record)):
if intip in record[i].split(',')[0]:
hostname = record[1].split('.')[0]
domainName = record[1].split('.')[1] + '.' + record[1].split('.')[2].strip(' ')
intDnsServer = record[0].split(',')[0]
intdelRecordcmd = 'dnscmd ' + intDnsServer +' /RecordDelete ' + domainName + ' ' + hostname + ' 900 A ' + intip +' /f'
if len(record[0].split(',')) == 2:
extip = record[i].split(',')[1]
extDnsServer = record[0].split(',')[1]
extdelRecordcmd = 'dnscmd ' + extDnsServer +' /RecordDelete ' + domainName + ' ' + hostname + ' 900 A ' + extip +' /f'
delRecordcmd = [intdelRecordcmd, extdelRecordcmd]
return delRecordcmd
#Generate Add A Record command line.
def addRecord(record):
intaddRecordcmd = ''
extaddRecordcmd = ''
#ping Hostname
pingResult = pingTest(record[1])
if pingResult:
addRecordcmd = [intaddRecordcmd, extaddRecordcmd]
return addRecordcmd
time.sleep(10)
if pingResult:
addRecordcmd = [intaddRecordcmd, extaddRecordcmd]
return addRecordcmd
for i in range(2,len(record)):
#Ping IP address
pingResult = pingTest(record[i].split(',')[0])
if pingResult:
hostname = record[1].split('.')[0]
domainName = record[1].split('.')[1] + '.' + record[1].split('.')[2].strip(' ')
intIp = record[i].split(',')[0]
intDnsServer = record[0].split(',')[0]
intaddRecordcmd = 'dnscmd ' + intDnsServer + ' /RecordAdd ' + domainName + ' ' + hostname + ' 900 A ' + intIp
if len(record[0].split(',')) == 2:
extIp = record[i].split(',')[1]
extDnsServer = record[0].split(',')[1]
extaddRecordcmd = 'dnscmd ' + extDnsServer + ' /RecordAdd ' + domainName + ' ' + hostname + ' 900 A ' + extIp
addRecordcmd = [intaddRecordcmd, extaddRecordcmd]
return addRecordcmd
def main():
intcmdLines = []
extcmdLines = []
try:
recordFile = open('testRecordList.txt','r')
recordLines = recordFile.readlines()
finally:
recordFile.close()
for recordLine in recordLines:
if recordLine.startswith('#'):
continue
if len(recordLine.strip(' ').strip('\n'))== 0:
continue
record = recordLine.strip('\n').split(';')
currentAIp = getARecordIp(record[1])
if currentAIp == 'Failed':
time.sleep(10)
currentAIp = getARecordIp(record[1])
if currentAIp == 'Failed':
addRecordcmd = addRecord(record)
if addRecordcmd[0]:
intcmdLines.append(addRecordcmd[0])
if addRecordcmd[1]:
extcmdLines.append(addRecordcmd[1])
continue
pingResult = pingTest(record[1])
if pingResult:
continue
time.sleep(10)
if pingResult:
continue
delRecordcmd = delRecord(record,currentAIp[0].strip('\n'))
if delRecordcmd[0]:
intcmdLines.append(delRecordcmd[0])
if delRecordcmd[1]:
extcmdLines.append(delRecordcmd[1])
addRecordcmd = addRecord(record)
if addRecordcmd[0]:
intcmdLines.append(addRecordcmd[0])
if addRecordcmd[1]:
extcmdLines.append(addRecordcmd[1])
if intcmdLines:
try:
logFile = open("changeintdnslog.txt","a")
cmdFile = open("updateintdns.bat","w")
for line in intcmdLines:
cmdFile.write(line+'\n')
logFile.write(time.strftime("%m-%d-%Y %H:%M:%S",time.localtime()) + '\n')
logFile.write(line+'\n\n')
finally:
logFile.close()
cmdFile.close()
intDnsServer = intcmdLines[0].split(' ')[1].strip(' ')
cpCmd = r"copy /V /Y updateintdns.bat \\" + intDnsServer + r"\taskscript"
os.popen(cpCmd)
if extcmdLines:
try:
logFile = open("changeextdnslog.txt","a")
cmdFile = open("updateextdns.bat","w")
for line in extcmdLines:
cmdFile.write(line+'\n')
logFile.write(time.strftime("%m-%d-%Y %H:%M:%S",time.localtime()) + '\n')
logFile.write(line+'\n\n')
finally:
logFile.close()
cmdFile.close()
extDnsServer = extcmdLines[0].split(' ')[1].strip(' ')
cpCmd = r"copy /V /Y updateextdns.bat \\" + extDnsServer + r"\taskscript"
os.popen(cpCmd)
if __name__ == "__main__":
main()
