Small discovery of OSPF election process

 

R1 (config) # router ospf 10

R1 (config-router) # net 192.168.12.0 0.0.255 a 0

R1 (config-router )#

* Dec 6 05:51:32. 975: OSPF: Interface Ethernet0/0 going Up

* Dec 6 05:51:32. 975: OSPF: Send hello to 224.0.0.5 area 0 on Ethernet0/0 from 192.168.12.1

* Dec 6 05:51:33. 475: OSPF: Build router LSA for area 0, router ID 1.1.1.1, seq 0x80000001, process 10

R1 (config-router )#

* Dec 6 05:51:42. 807: OSPF: Send hello to 224.0.0.5 area 0 on Ethernet0/0 from 192.168.12.1

R1 (config-router )#

* Dec 6 05:51:52. 179: OSPF: Send hello to 224.0.0.5 area 0 on Ethernet0/0 from 192.168.12.1

R1 (config-router )#

* Dec 6 05:52:01. 335: OSPF: Send hello to 224.0.0.5 area 0 on Ethernet0/0 from 192.168.12.1

R1 (config-router )#

* Dec 6 05:52:10. 907: OSPF: Send hello to 224.0.0.5 area 0 on Ethernet0/0 from 192.168.12.1

R1 (config-router )#

 

* Dec 6 05:52:12. 975: OSPF: end of Wait on interface Ethernet0/0

 

* Dec 6 05:52:12. 975: OSPF: DR/BDR election on Ethernet0/0

* Dec 6 05:52:12. 975: OSPF: Elect BDR 1.1.1.1

* Dec 6 05:52:12. 975: OSPF: Elect DR 1.1.1.1

* Dec 6 05:52:12. 975: OSPF: Elect BDR 0.0.0.0

* Dec 6 05:52:12. 975: OSPF: Elect DR 1.1.1.1

* Dec 6 05:52:12. 975: DR: 1.1.1.1 (Id) BDR: none

* Dec 6 05:52:13. 475: OSPF: No full nbrs to build NetLSA for interface Ethernet0/0

R1 (config-router )#

 

 

The peer R2 has not enabled OSPF yet. At this time, it will find that the e0/0 of R1 will wait for a while, and then it will look like 40 s. If it cannot detect its neighbors, it will elect its own DR. "End of Wait on interface Ethernet0/0"

 

When 0/0 of R1 is disabled, the following information is displayed: "Remember old DR 1.1.1.1 (id )"

 

R1 (config) # int e 0/0

R1 (config-if )#

* Dec 6 06:10:24. 575: OSPF: Send hello to 224.0.0.5 area 0 on Ethernet0/0 from 192.168.12.1

R1 (config-if) # shut

R1 (config-if )#

* Dec 6 06:10:27. 903: OSPF: Ethernet0/0: Route adjust notification: DOWN/DOWN

* Dec 6 06:10:27. 903: OSPF: Interface Ethernet0/0 going Down

* Dec 6 06:10:27. 903: OSPF: 1.1.1.1 address 192.168.12.1 on Ethernet0/0 is dead, state DOWN

* Dec 6 06:10:27. 903: OSPF: Neighbor change Event on interface Ethernet0/0

* Dec 6 06:10:27. 903: OSPF: DR/BDR election on Ethernet0/0

* Dec 6 06:10:27. 903: OSPF: Elect BDR 0.0.0.0

* Dec 6 06:10:27. 903: OSPF: Elect DR 0.0.0.0

* Dec 6 06:10:27. 903: OSPF: Elect BDR 0.0.0.0

* Dec 6 06:10:27. 903: OSPF: Elect DR 0.0.0.0

* Dec 6 06:10:27. 903: DR: none BDR: none

* Dec 6 06:10:27. 903: OSPF: Flush network LSA immediately

R1 (config-if) # exit

R1 (config )#

* Dec 6 06:10:27. 903: OSPF: Remember old DR 1.1.1.1 (id)

* Dec 6 06:10:27. 903: OSPF: Ethernet0/0: Interface state change to DOWN, new ospf state DOWN

* Dec 6 06:10:28. 403: OSPF: We are not DR to build Net LSA for interface Ethernet0/0

* Dec 6 06:10:28. 403: OSPF: Build router LSA for area 0, router ID 1.1.1.1, seq 0x80000002, process 10

R1 (config) # exit

R1 #

R1 #

* Dec 6 06:10:29. 903: % LINK-5-CHANGED: Interface Ethernet0/0, changed state to administratively down

* Dec 6 06:10:30. 119: % SYS-5-CONFIG_ I: Configured from console by console

* Dec 6 06:10:30. 907: % LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/0, changed state to down

R1 #

From the above log, we will find that R1 records an old DR, which will be enabled only when the corresponding ospf port is enabled and no more appropriate DR is available, when I want to repeat the first step of the experiment, because there is no neighbor, the recorded DR will be enabled directly, and when there is a neighbor, new DR and BDR will be negotiated, as shown below:

 

R1 (config-if )#

* Dec 6 06:11:51. 175: % LINK-3-UPDOWN: Interface Ethernet0/0, changed state to up

* Dec 6 06:11:52. 175: % LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/0, changed state to up

* Dec 6 06:11:52. 175: OSPF: Ethernet0/0: Route adjust notification: UP/UP

* Dec 6 06:11:52. 175: OSPF: Interface Ethernet0/0 going Up

* Dec 6 06:11:52. 175: OSPF: Send hello to 224.0.0.5 area 0 on Ethernet0/0 from 192.168.12.1

* Dec 6 06:11:52. 175: OSPF: Ethernet0/0: Interface state change to UP, new ospf state WAIT

R1 (config-if )#

* Dec 6 06:11:52. 675: OSPF: Build router LSA for area 0, router ID 1.1.1.1, seq 0x80000003, process 10

R1 (config-if )#

* Dec 6 06:12:01. 787: OSPF: Send hello to 224.0.0.5 area 0 on Ethernet0/0 from 192.168.12.1

R1 (config-if )#

* Dec 6 06:12:07. 299: OSPF: Rcv hello from 2.2.2.2 area 0 from Ethernet0/0 192.168.12.2

* Dec 6 06:12:07. 299: OSPF: Send immediate hello to nbr 2.2.2.2, src address 192.168.12.2, on Ethernet0/0

* Dec 6 06:12:07. 299: OSPF: Send hello to 192.168.12.2 area 0 on Ethernet0/0 from 192.168.12.1

* Dec 6 06:12:07. 299: OSPF: End of hello processing

R1 (config-if )#

* Dec 6 06:12:11. 263: OSPF: Send hello to 224.0.0.5 area 0 on Ethernet0/0 from 192.168.12.1

* Dec 6 06:12:11. 263: OSPF: Rcv hello from 2.2.2.2 area 0 from Ethernet0/0 192.168.12.2

* Dec 6 06:12:11. 263: OSPF: 2 Way Communication to 2.2.2.2 on Ethernet0/0, state 2WAY

* Dec 6 06:12:11. 263: OSPF: End of hello processing

R1 (config-if )#

* Dec 6 06:12:17. 139: OSPF: Rcv hello from 2.2.2.2 area 0 from Ethernet0/0 192.168.12.2

* Dec 6 06:12:17. 139: OSPF: End of hello processing

R1 (config-if )#

* Dec 6 06:12:20. 587: OSPF: Send hello to 224.0.0.5 area 0 on Ethernet0/0 from 192.168.12.1

R1 (config-if )#

* Dec 6 06:12:26. 871: OSPF: Rcv hello from 2.2.2.2 area 0 from Ethernet0/0 192.168.12.2

* Dec 6 06:12:26. 871: OSPF: End of hello processing

R1 (config-if )#

* Dec 6 06:12:30. 579: OSPF: Send hello to 224.0.0.5 area 0 on Ethernet0/0 from 192.168.12.1

R1 (config-if )#

* Dec 6 06:12:32. 175: OSPF: end of Wait on interface Ethernet0/0

* Dec 6 06:12:32. 175: OSPF: DR/BDR election on Ethernet0/0

* Dec 6 06:12:32. 175: OSPF: Elect BDR 2.2.2.2

* Dec 6 06:12:32. 175: OSPF: Elect DR 2.2.2.2

* Dec 6 06:12:32. 175: DR: 2.2.2.2 (Id) BDR: 2.2.2.2 (Id)

* Dec 6 06:12:32. 175: OSPF: Ethernet0/0 Nbr 2.2.2.2: Prepare dbase exchange

* Dec 6 06:12:32. 175: OSPF: Send DBD to 2.2.2.2 on Ethernet0/0 seq 0x24BF opt 0x52 flag 0x7 len 32

R1 (config-if )#

* Dec 6 06:12:36. 339: OSPF: Rcv hello from 2.2.2.2 area 0 from Ethernet0/0 192.168.12.2

* Dec 6 06:12:36. 339: OSPF: End of hello processing

* Dec 6 06:12:36. 983: OSPF: Send DBD to 2.2.2.2 on Ethernet0/0 seq 0x24BF opt 0x52 flag 0x7 len 32

* Dec 6 06:12:36. 983: OSPF: Retransmitting DBD to 2.2.2.2 on Ethernet0/0 [1]

R1 (config-if )#

* Dec 6 06:12:39. 727: OSPF: Send hello to 224.0.0.5 area 0 on Ethernet0/0 from 192.168.12.1

R1 (config-if )#

* Dec 6 06:12:41. 559: OSPF: Send DBD to 2.2.2.2 on Ethernet0/0 seq 0x24BF opt 0x52 flag 0x7 len 32

* Dec 6 06:12:41. 559: OSPF: Retransmitting DBD to 2.2.2.2 on Ethernet0/0 [2]

R1 (config-if )#

* Dec 6 06:12:45. 919: OSPF: Rcv hello from 2.2.2.2 area 0 from Ethernet0/0 192.168.12.2

* Dec 6 06:12:45. 919: OSPF: End of hello processing

* Dec 6 06:12:46. 419: OSPF: Send DBD to 2.2.2.2 on Ethernet0/0 seq 0x24BF opt 0x52 flag 0x7 len 32

* Dec 6 06:12:46. 419: OSPF: Retransmitting DBD to 2.2.2.2 on Ethernet0/0 [3]

* Dec 6 06:12:47. 303: OSPF: Rcv DBD from 2.2.2.2 on Ethernet0/0 seq 0x22F9 opt 0x52 flag 0x7 len 32 mtu 1500 state EXSTART

* Dec 6 06:12:47. 303: OSPF: NBR Negotiation Done. We are the SLAVE

* Dec 6 06:12:47. 303: OSPF: Ethernet0/0 Nbr 2.2.2.2: Summary list built, size 1

* Dec 6 06:12:47. 303: OSPF: Send DBD to 2.2.2.2 on Ethernet0/0 seq 0x22F9 opt 0x52 flag 0x2 len 52

* Dec 6 06:12:47. 311: OSPF: Rcv DBD from 2.2.2.2 on Ethernet0/0 seq 0x22FA opt 0x52 flag 0x1 len 52 mtu 1500 state EXCHANGE

* Dec 6 06:12:47. 311: OSPF: Exchange Done with 2.2.2.2 on Ethernet0/0

* Dec 6 06:12:47. 311: OSPF: Send ls req to 2.2.2.2 length 12 LSA count 1

* Dec 6 06:12:47. 311: OSPF: Send DBD to 2.2.2.2 on Ethernet0/0 seq 0x22FA opt 0x52 flag 0x0 len 32

* Dec 6 06:12:47. 319: OSPF: Rcv ls upd from 2.2.2.2 on Ethernet0/0 length 64 LSA count 1

* Dec 6 06:12:47. 319: OSPF: Synchronized with 2.2.2.2 on Ethernet0/0, state FULL

* Dec 6 06:12:47. 319: % OSPF-5-ADJCHG: Process 10, Nbr 2.2.2.2 on Ethernet0/0 from LOADING to FULL, Loading Done

R1 (config-if )#

* Dec 6 06:12:47. 319: OSPF: Rcv ls req from 2.2.2.2 on Ethernet0/0 length 36 LSA count 1

* Dec 6 06:12:47. 819: OSPF: Build router LSA for area 0, router ID 1.1.1.1, seq 0x80000004, process 10

R1 (config-if )#

* Dec 6 06:12:49. 183: OSPF: Send hello to 224.0.0.5 area 0 on Ethernet0/0 from 192.168.12.1

R1 (config-if) # ^ Z

R1 # un

* Dec 6 06:12:54. 275: % SYS-5-CONFIG_ I: Configured from console by console

R1 # undbug

* Dec 6 06:12:55. 599: OSPF: Rcv hello from 2.2.2.2 area 0 from Ethernet0/0 192.168.12.2

* Dec 6 06:12:55. 599: OSPF: Neighbor change Event on interface Ethernet0/0

* Dec 6 06:12:55. 599: OSPF: DR/BDR election on Ethernet0/0

* Dec 6 06:12:55. 599: OSPF: Elect BDR 1.1.1.1

* Dec 6 06:12:55. 599: OSPF: Elect DR 2.2.2.2

* Dec 6 06:12:55. 599: OSPF: Elect BDR 1.1.1.1

* Dec 6 06:12:55. 599: OSPF: Elect DR 2.2.2.2

* Dec 6 06:12:55. 599: DR: 2.2.2.2 (Id) BDR: 1.1.1.1 (Id)

* Dec 6 06:12:55. 599: OSPF: Neighbor change Event on interface Ethernet0/0

* Dec 6 06:12:55. 599: OSPF: DR/BDR election on Ethernet0/0

* Dec 6 06:12:55. 599: OSPF: Elect BDR 1.1.1.1

R1 # undb

* Dec 6 06:12:55. 599: OSPF: Elect DR 2.2.2.2

* Dec 6 06:12:55. 599: DR: 2.2.2.2 (Id) BDR: 1.1.1.1 (Id)

* Dec 6 06:12:55. 599: OSPF: End of hello processing

R1 # undb

R1 # un

* Dec 6 06:12:58. 607: OSPF: Send hello to 224.0.0.5 area 0 on Ethernet0/0 from 192.168.12.1

R1 # unde

R1 # undebug all

 

 

This article is from the "cafe" blog