I was troubleshooting an OSPF area range summarization and came upon something I haven’t seen before called Passive Advertisement. There weren’t too many Cisco documents that explained it so I decided to post a really quick description explaining it in little detail and where you could see it . This could be useful for the CCIE troubleshooting section, when dealing with OSPF area summarization problems.
I will use R3 to demonstrate. This router is connected to area 0 and area 1 which makes it the only ABR connecting the two areas. R3 should be sending a summary route 220.127.116.11/16 for the two component routes 18.104.22.168/24 and 22.214.171.124/24. Looks pretty simple. To verify, I check the output of show ip ospf to make sure the area 0 range 126.96.36.199 255.255.0.0 command is configured: