How to convert OSPF area ID from decimal to IP address format - easy steps

How to convert OSPF area ID from decimal to IP address format - easy steps

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Created On 09/25/18 19:49 PM - Last Modified 07/19/22 23:07 PM


Symptom


  • Some vendor's devices have configured the OSPF area in decimal format.
  • Palo Alto Networks Firewall accepts OSPF area in 32 bit IP address format.

Environment


  • Palo Alto Firewall.
  • Any PAN-OS.
  • OSPF configuration.

Resolution


Solution 1:
  1. Take a packet capture and go through the OSPF fields. This will display the OSPF area in dotted decimal format
  2. Configure the same area-id on Palo Alto Firewall.
Example: The following configuration has an area-id of 777. Packet captures display the area-id in a dotted-decimal format which is 0.0.3.9 
#router ospf 100
#network 0.0.0.0 255.255.255.255 area 777
OSPF packet capture 
Solution 2:
  1. Convert the decimal format to binary. In the above example Decimal 777 = Binary 1100001001
  2. Prepend leading 0s to the binary number and separate them into 4 octets. The above will be 00000000 00000000 00000011 00001001
  3. Convert the binary to a dotted-decimal format which is 0.0.3.9
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