Interface Failover Script via Monitor

 
 !/bin/bash 
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  This script is a F5 external monitor to failover the NICs in case of a cable or switch problem. 
  
  Using a spanning tree protocol or 802.3ad would be the preferred method of NIC redundancy. If 
  these protocols is not supported in the environment this script can be used. 
  
  The script expects the two interfaces to provide redundancy on as input parameters, eg. 1.1 1.2 
  
  Last updated 18/02/2010 
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  Check if 4 parameters were passed to the script 
 if [ "$" != "4" ]; then 
  logger -p local0.warning  "Interface Failover: Only supply two interfaces" 
  exit 1 
 fi 
  
  Check if there is already a copy of the monitor running, monitors will fire on the specified interval regardless if it's still running 
  It sometimes takes a couple of seconds for the interface to come up, this check will prevenet a flip flop between the two NICs 
 if pgrep int_fail > /dev/null; then 
  logger -p local0.warning  "Interface Failover: Script already running, aborting" 
  exit 1 
 fi 
  
  Ignore the 2 default parameters passed by the monitor 
 shift 
 shift 
  
  Setup variables 
 interfaces="$*" 
 state="false" 
 state2="false" 
 state3="false" 
  
  Output interface status to temporary file 
 b interface all show all | grep INTERFACE > /tmp/b_interface_show 
  
  Read statuses from above command into variables 
 int1_status=`grep "^INTERFACE *$1 " /tmp/b_interface_show | awk '{print $5}' | tr '[:lower:]' '[:upper:]'` 
 int1_config=`grep "^INTERFACE *$1 " /tmp/b_interface_show | awk '{print $4}'` 
 int2_status=`grep "^INTERFACE *$2 " /tmp/b_interface_show | awk '{print $5}' | tr '[:lower:]' '[:upper:]'` 
 int2_config=`grep "^INTERFACE *$2 " /tmp/b_interface_show | awk '{print $4}'` 
  
  Check if both interfaces ae enabled, this will cause a loop on the network 
 if [ "$int1_config" == "ENABLED" ] && [ "$int2_config" == "ENABLED" ]; then 
   logger -p local0.warning  "Interface Failover: ERROR: Only one interface should be enabled" 
   exit 1 
 fi 
  
  Check if interface 1 is down and enabled and interface 2 disabled; if this is the case a failover need to happen 
 if [ "$int1_status" == "DOWN" ] && [ "$int1_config" == "ENABLED" ] && [ "$int2_config" == "DISABLED" ]; then 
   logger -p local0.warning  "Interface Failover: Interface $1 is $int1_config and $int1_status" 
   logger -p local0.warning  "Interface Failover: Disabling interface $1" 
  Disable interface 1 
   b interface $1 disable 
  
  Loop for 5 seconds or until interface 1 is disabled 
   for i in {1..5} 
   do 
  Output interface 1 status to temporary file 
    b interface $1 show all | grep INTERFACE > /tmp/b_interface_$1_show 
  Read status from above command into variable 
    config=`grep "^INTERFACE *$1 " /tmp/b_interface_$1_show | awk '{print $4}'` 
  Check if interface 1 is disabled 
     if [ "$config" == "DISABLED" ]; then 
      logger -p local0.warning  "Interface Failover: Enabling interface $2" 
      state3="true" 
  Enable interface 2 after confirming interface 1 is down 
      b interface $2 enable 
      break 
     fi 
    sleep 1s 
   done 
    
  If the interface was not enabled in 5 seconds abort the script 
  if ["$state3" == "false"]; then 
   logger -p local0.warning  "Interface Failover: Error: Unable to disable interface $1" 
   exit 1 
  fi 
  
  Loop for 5 seconds or until interface 2 is enabled 
   for i in {1..5} 
   do 
  Output interface 2 status to temporary file 
    b interface $2 show all | grep INTERFACE > /tmp/b_interface_$2_show 
  Read status from above command into variable 
    config=`grep "^INTERFACE *$2 " /tmp/b_interface_$2_show | awk '{print $4}'` 
  Check if interface 2 is enabled 
     if [ "$config" == "ENABLED" ]; then 
      logger -p local0.warning  "Interface Failover: Interface $2 enabled" 
      state="true" 
      break 
     fi 
    sleep 1s 
   done 
  
  If the interface was not enabled in 5 seconds abort the script 
  if ["$state" == "false"]; then 
   logger -p local0.warning  "Interface Failover: Error: Unable to enable interface $2" 
   exit 1 
  fi 
  
 Waiting for 30 seconds for the interface to come up 
   for i in {1..30} 
   do 
  Output interface 2 status to temporary file 
    b interface $2 show all | grep INTERFACE > /tmp/b_interface_$2_show 
  Read status from above command into variable 
    status=`grep "^INTERFACE *$2 " /tmp/b_interface_$2_show | awk '{print $5}' | tr '[:lower:]' '[:upper:]'` 
  Check if interface 2 is up 
     if [ "$status" == "UP" ]; then 
      logger -p local0.warning  "Interface Failover: Interface $2 UP" 
      state2="true" 
      break 
     fi 
    sleep 1s 
   done 
  
  If the interface did not come up in 30 seconds abort the script 
  if ["$state2" == "false"]; then 
   logger -p local0.warning  "Interface Failover: Error: Interface $2 not coming UP" 
   exit 1 
  fi 
  
 fi 
  
  Check if interface 2 is down and enabled and interface 1 disabled; if this is the case a failover need to happen 
 if [ "$int2_status" == "DOWN" ] && [ "$int2_config" == "ENABLED" ] && [ "$int1_config" == "DISABLED" ]; then 
   logger -p local0.warning  "Interface Failover: Interface $2 is $int2_config and $int2_status" 
   logger -p local0.warning "Interface Failover: Disabling interface $2" 
   b interface $2 disable 
  
  Loop for 5 seconds or until interface 1 is disabled 
   for i in {1..5} 
   do 
  Output interface 2 status to temporary file 
    b interface $2 show all | grep INTERFACE > /tmp/b_interface_$2_show 
  Read status from above command into variable 
    config=`grep "^INTERFACE *$2 " /tmp/b_interface_$2_show | awk '{print $4}'` 
  Check if interface 2 is disabled 
     if [ "$config" == "DISABLED" ]; then 
      logger -p local0.warning "Interface Failover: Enabling interface $1" 
      state3="true" 
  Enable interface 1 after confirming interface 2 is down 
      b interface $1 enable 
      break 
     fi 
    sleep 1s 
   done 
    
  If the interface was not enabled in 5 seconds abort the script 
  if ["$state3" == "false"]; then 
   logger -p local0.warning  "Interface Failover: Error: Unable to disable interface $2" 
   exit 1 
  fi 
  
  Loop for 5 seconds or until interface 1 is enabled 
   for i in {1..5} 
   do 
  Output interface 1 status to temporary file 
    b interface $1 show all | grep INTERFACE > /tmp/b_interface_$1_show 
  Read status from above command into variable 
    config=`grep "^INTERFACE *$1 " /tmp/b_interface_$1_show | awk '{print $4}'` 
  Check if interface 1 is enabled 
     if [ "$config" == "ENABLED" ]; then 
      logger -p local0.warning  "Interface Failover: Interface $1 enabled" 
      state="true" 
      break 
     fi 
    sleep 1s 
   done 
  
   If the interface was not enabled in 5 seconds abort the script 
  if ["$state" == "false"]; then 
   logger -p local0.warning  "Interface Failover: Error: Unable to enable interface $1" 
   exit 1 
  fi 
  
 Waiting for 30 seconds for the interface to come up 
   for i in {1..30} 
   do 
  Output interface 1 status to temporary file 
    b interface $1 show all | grep INTERFACE > /tmp/b_interface_$1_show 
  Read status from above command into variable 
    status=`grep "^INTERFACE *$1 " /tmp/b_interface_$1_show | awk '{print $5}' | tr '[:lower:]' '[:upper:]'` 
  Check if interface 1 is up 
     if [ "$status" == "UP" ]; then 
      logger -p local0.warning  "Interface Failover: Interface $1 UP" 
      state2="true" 
      break 
     fi 
    sleep 1s 
   done 
  
  If the interface did not come up in 30 seconds abort the script 
  if ["$state2" == "false"]; then 
   logger -p local0.warning  "Interface Failover: Error: Interface $1 not coming UP" 
   exit 1 
  fi 
  
 fi 
  
  Remove temporary files 
 rm /tmp/b_interface_$1_show 
 rm /tmp/b_interface_$2_show 
 rm /tmp/b_interface_show 
  
  Monitor expects output of "up"; no return value will mark the monitor down 
 echo "up" 
 exit 0