Configuring OSPF in a Single Area · Here is a summary of my link-state database. DBD...
Transcript of Configuring OSPF in a Single Area · Here is a summary of my link-state database. DBD...
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5-1© 2001, Cisco Systems, Inc.
Configuring OSPF in a Single Area
Configuring OSPF in a Single Area
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OSPF OverviewOSPF Overview
© 2001, Cisco Systems, Inc. 5-2
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BSCI v1.2— 5-3© 2001, Cisco Systems, Inc.
• Has fast convergence
• Supports VLSM
• Processes updates efficiently
• Selects paths based on bandwidth
• Supports equal-cost multipath
What Is OSPF?What Is OSPF?
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BSCI v1.2— 5-4© 2001, Cisco Systems, Inc.
OSPF in IP PacketsOSPF in IP Packets
OSPF is a link-state routing protocol• Relies on IP packets for delivery of
routing information
• Uses protocol number 89
IP Header
Protocol Number
Frame Header
CRCPacket Payload
Frame Payload
89—OSPF 6—TCP17—UDP
89—OSPF 6—TCP17—UDP
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OSPF TerminologyOSPF Terminology
© 2001, Cisco Systems, Inc. 5-5
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BSCI v1.2— 5-6© 2001, Cisco Systems, Inc.
OSPF TerminologyOSPF Terminology
TokenRing
Interfaces
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BSCI v1.2— 5-7© 2001, Cisco Systems, Inc.
OSPF Terminology (cont.)OSPF Terminology (cont.)
Neighbors
TokenRing
Interfaces
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BSCI v1.2— 5-8© 2001, Cisco Systems, Inc.
Neighbors
TokenRing
Interfaces
OSPF Terminology (cont.)OSPF Terminology (cont.)
Cost = 10
Cost = 6Cost = 1785
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BSCI v1.2— 5-9© 2001, Cisco Systems, Inc.
OSPF Terminology (cont.)OSPF Terminology (cont.)
Neighbors
TokenRing
Interfaces
Area 1Area 0
Cost = 10
Cost = 6Cost = 1785
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BSCI v1.2— 5-10© 2001, Cisco Systems, Inc.
OSPF Terminology (cont.)OSPF Terminology (cont.)
Autonomous System
Neighbors
TokenRing
Interfaces
Area 1Area 0
Cost = 1785
Cost = 10
Cost = 6
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BSCI v1.2— 5-11© 2001, Cisco Systems, Inc.
Autonomous System
OSPF Terminology (cont.)OSPF Terminology (cont.)
Neighborship Database
Lists Neighbors
Neighbors
TokenRing
Interfaces
Area 1Area 0
Cost = 10
Cost = 6Cost = 1785
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BSCI v1.2— 5-12© 2001, Cisco Systems, Inc.
Autonomous System
OSPF Terminology (cont.)OSPF Terminology (cont.)
Topology Database
Lists All Routes
Neighborship Database
Lists Neighbors
Neighbors
TokenRing
Interfaces
Area 1Area 0
Cost = 1785
Cost = 10
Cost = 6
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BSCI v1.2— 5-13© 2001, Cisco Systems, Inc.
Autonomous System
OSPF Terminology (cont.)OSPF Terminology (cont.)
RoutingTable
Lists Best Routes
Topology Database
Lists All Routes
Neighborship Database
Lists Neighbors
Cost = 10
Cost = 1785 Cost = 6
Neighbors
TokenRing
Interfaces
Area 1Area 0
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OSPF OperationOSPF Operation
© 2001, Cisco Systems, Inc. 5-14
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BSCI v1.2— 5-15© 2001, Cisco Systems, Inc.
OSPF TopologiesOSPF Topologies
Point-to-Point
NBMA
Broadcast Multiaccess
X.25Frame Relay
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OSPF Operation in a Broadcast Multiaccess Topology
OSPF Operation in a Broadcast Multiaccess Topology
© 2001, Cisco Systems, Inc. 5-16
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BSCI v1.2— 5-17© 2001, Cisco Systems, Inc.
NeighborshipNeighborship
Hello
afadjfjorqpoeru39547439070713
Router IDHello/dead intervalsNeighborsArea-IDRouter priorityDR IP addressBDR IP addressAuthentication passwordStub area flag
* *
**
* Entry must match on neighboring routers
Hello
AA
DD EE
CCBB
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BSCI v1.2— 5-18© 2001, Cisco Systems, Inc.
Neighborship (cont.)Neighborship (cont.)
Hello
afadjfjorqpoeru39547439070713
Router IDHello/dead intervalsNeighborsArea-IDRouter priorityDR IP addressBDR IP addressAuthentication passwordStub area flag
**
**
* Entry must match on neighboring routers
Hello
AA
DD EE
CCBB
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BSCI v1.2— 5-19© 2001, Cisco Systems, Inc.
DR and BDRDR and BDR
DR BDR
• Hellos elect DR and BDR to represent segment• Each router then forms adjacency with DR
and BDR
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BSCI v1.2— 5-20© 2001, Cisco Systems, Inc.
• Hello packets exchanged via IP multicast • Router with highest OSPF priority elected
P=1 P=0P=1
Electing the DR and BDRElecting the DR and BDR
P=3 P=2
Hello
DR BDR
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BSCI v1.2— 5-21© 2001, Cisco Systems, Inc.
Exchange ProcessExchange Process
172.16.5.1/24E0
172.16.5.2/24E1A B
Down State
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BSCI v1.2— 5-22© 2001, Cisco Systems, Inc.
Exchange ProcessExchange Process
172.16.5.1/24E0
172.16.5.2/24E1
Router BNeighbors List
172.16.5.1/24, int E1
I am router ID 172.16.5.1 and I see no one.Down State
Init State
A B
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BSCI v1.2— 5-23© 2001, Cisco Systems, Inc.
Exchange ProcessExchange Process
172.16.5.1/24E0
I am router ID 172.16.5.2, and I see 172.16.5.1.
172.16.5.2/24E1
Router BNeighbors List
172.16.5.1/24, int E1
I am router ID 172.16.5.1 and I see no one.Down State
Init State
A B
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BSCI v1.2— 5-24© 2001, Cisco Systems, Inc.
Exchange ProcessExchange Process
172.16.5.1/24E0
I am router ID 172.16.5.2, and I see 172.16.5.1.
Router ANeighbors List
172.16.5.2/24, int E0
172.16.5.2/24E1
Router BNeighbors List
172.16.5.1/24, int E1
I am router ID 172.16.5.1 and I see no one.Down State
Init State
Two-Way State
A B
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BSCI v1.2— 5-25© 2001, Cisco Systems, Inc.
Discovering RoutesDiscovering Routes
E0172.16.5.1
DR
E0172.16.5.3
No, I will start exchange because I have a higher router ID.
I will start exchange because I have router ID 172.16.5.1.Hello
afadjfjorqpoeru39547439070713
Hello
afadjfjorqpoeru39547439070713
Exstart State
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BSCI v1.2— 5-26© 2001, Cisco Systems, Inc.
Discovering RoutesDiscovering Routes
Here is a summary of my link-state database. DBD
afadjfjorqpoeru39547439070713
Exchange State
Here is a summary of my link-state database.DBD
afadjfjorqpoeru39547439070713
E0172.16.5.1
E0172.16.5.3
No, I will start exchange because I have a higher router ID.
I will start exchange because I have router ID 172.16.5.1.Hello
afadjfjorqpoeru39547439070713
Hello
afadjfjorqpoeru39547439070713
Exstart State
DR
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BSCI v1.2— 5-27© 2001, Cisco Systems, Inc.
Discovering Routes (cont.)Discovering Routes (cont.)
E0172.16.5.1
E0172.16.5.3
Thanks for the information!LSAck
afadjfjorqpoeru39547439070713
LSAck
afadjfjorqpoeru39547439070713
DR
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BSCI v1.2— 5-28© 2001, Cisco Systems, Inc.
Discovering Routes (cont.)Discovering Routes (cont.)
I need the complete entry for network 172.16.6.0/24.
Here is the entry for network 172.16.6.0/24.
Thanks for the information!
LSR
afadjfjorqpoeru39547439070713
LSAck
afadjfjorqpoeru39547439070713
LSU
afadjfjorqpoeru39547439070713
Loading State
E0172.16.5.1
E0172.16.5.3
Thanks for the information!LSAck
afadjfjorqpoeru39547439070713
LSAck
afadjfjorqpoeru39547439070713
DR
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BSCI v1.2— 5-29© 2001, Cisco Systems, Inc.
Discovering Routes (cont.)Discovering Routes (cont.)
Full State
I need the complete entry for network 172.16.6.0/24.
Here is the entry for network 172.16.6.0/24.
Thanks for the information!
LSR
afadjfjorqpoeru39547439070713
LSAck
afadjfjorqpoeru39547439070713
LSU
afadjfjorqpoeru39547439070713
Loading State
E0172.16.5.1
E0172.16.5.3
Thanks for the information!LSAck
afadjfjorqpoeru39547439070713
LSAck
afadjfjorqpoeru39547439070713
DR
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BSCI v1.2— 5-30© 2001, Cisco Systems, Inc.
Choosing RoutesChoosing Routes
Topology TableNet Cost Out Interface10.2.2.0 7 To010.3.3.0 17 To010.3.3.0 20 E0
TokenRing
Cost=10
Cost=6FDDI
Cost=1
A B C
This is the best route to 10.3.3.0.
10.1.1.0/24 10.2.2.0/24 10.3.3.0/24
10.4.4.0/24
Cost=10
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BSCI v1.2— 5-31© 2001, Cisco Systems, Inc.
Maintaining Routing InformationMaintaining Routing Information
Router A notifies all OSPF DRs on 224.0.0.6
xx
Link-State Change
LSU1
DR
AB
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BSCI v1.2— 5-32© 2001, Cisco Systems, Inc.
LSU
2
• Router A notifies all OSPF DRs on 224.0.0.6
• DR notifies others on 224.0.0.5
xx
Link-State Change
LSU1
Maintaining Routing Information (cont.)
Maintaining Routing Information (cont.)
DR
AB
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BSCI v1.2— 5-33© 2001, Cisco Systems, Inc.
LSU
3
LSU
2
xx
Link-State Change
LSU1
• Router A notifies all OSPF DRs on 224.0.0.6
• DR notifies others on 224.0.0.5
Maintaining Routing Information (cont.)
Maintaining Routing Information (cont.)
DR
AB
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BSCI v1.2— 5-34© 2001, Cisco Systems, Inc.
I need to update my routing table.
4
LSU
3
LSU
2
xx
Link-State Change
LSU1
• Router A notifies all OSPF DRs on 224.0.0.6
• DR notifies others on 224.0.0.5
Maintaining Routing Information (cont.)
Maintaining Routing Information (cont.)
DR
AB
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BSCI v1.2— 5-35© 2001, Cisco Systems, Inc.
Maintaining Routing Information (cont.)
Maintaining Routing Information (cont.)
Is entry inlink-state
database?LSA
LSU
No
Run SPF to calculate new routing table
Add to database
Flood LSA
End
Send LSAckto DR
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BSCI v1.2— 5-36© 2001, Cisco Systems, Inc.
Yes
Is seq. # the same?
Yes
Ignore LSAIs entry inlink-state
database?LSA
LSU
No
Run SPF to calculate new routing table
Add to database
Flood LSA
Send LSAckto DR
End
Maintaining Routing Information (cont.)
Maintaining Routing Information (cont.)
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BSCI v1.2— 5-37© 2001, Cisco Systems, Inc.
No
Send LSUwith newer
information to source
Is seq. #higher?
No
Yes
Is seq. # the same?
Yes
Ignore LSAIs entry inlink-state
database?LSA
LSU
No
Run SPF to calculate new routing table
Add to database
Flood LSA
Send LSAckto DR
End End
Maintaining Routing Information (cont.)
Maintaining Routing Information (cont.)
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BSCI v1.2— 5-38© 2001, Cisco Systems, Inc.
Yes
Goto A
A
No
Send LSUwith newer
information to source
Is seq. #higher?
No
Yes
Is seq. # the same?
Yes
Ignore LSAIs entry inlink-state
database?LSA
LSU
No
Run SPF to calculate new routing table
Add to database
Flood LSA
Send LSAckto DR
End End
Maintaining Routing Information (cont.)
Maintaining Routing Information (cont.)
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BSCI v1.2— 5-39© 2001, Cisco Systems, Inc.
OSPF Operation in a Point-to-Point Topology
OSPF Operation in a Point-to-Point Topology
© 2001, Cisco Systems, Inc. 5-39
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BSCI v1.2— 5-40© 2001, Cisco Systems, Inc.
Point-to-Point NeighborshipPoint-to-Point Neighborship
• Router dynamically detects its neighboring router using the Hello protocol
• No election: Adjacency is automatic as soon as the two routers can communicate
• OSPF packets are always sent as multicast 224.0.0.5
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Configuring OSPF in a Single Area
Configuring OSPF in a Single Area
© 2001, Cisco Systems, Inc. 5-41
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BSCI v1.2— 5-42© 2001, Cisco Systems, Inc.
Configuring OSPF on Internal Routers
Configuring OSPF on Internal Routers
Can assign network or interface address.
Broadcast Network Point-to-Point Network
E0
10.64.0.1
10.64.0.2
E0
S0
10.2.1.210. 2.1.1
S1A B C
<Output Omitted>
interface Ethernet0ip address 10.64.0.1 255.255.255.0
!<Output Omitted>router ospf 1
network 10.0.0.0 0.255.255.255 area 0
<Output Omitted>
interface Ethernet0ip address 10.64.0.2 255.255.255.0
!interface Serial0ip address 10.2.1.2 255.255.255.0
<Output Omitted>router ospf 50network 10.2.1.2 0.0.0.0 area 0network 10.64.0.2 0.0.0.0 area 0
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BSCI v1.2— 5-43© 2001, Cisco Systems, Inc.
Router ID: • Number by which the router is known to OSPF• Default: The highest IP address on an active interface at the
moment of OSPF process startup• Can be overridden by a loopback interface: Highest IP address
of any active loopback interface
Advertised Loopback AddressEx: 172.16.17.5• In OSPF table • Uses address space• Can use ping
Unadvertised Loopback AddressEx: 192.168.255.254• Not in OSPF table• Saves address space• Cannot use ping
Network 172.16.0.0
Configuring Optional CommandsConfiguring Optional Commands
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BSCI v1.2— 5-44© 2001, Cisco Systems, Inc.
• Assigns a cost to an outgoing interface
• May be required for interoperability
• Uses default cost between Cisco devices
Cisco Non-Cisco
Traffic
TokenRing
Router(config-if)#
ip ospf cost cost
Configuring Optional Commands (cont.)
Configuring Optional Commands (cont.)
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BSCI v1.2— 5-45© 2001, Cisco Systems, Inc.
Configuring OSPF in Point-to-Point ModeConfiguring OSPF in Point-to-Point Mode
R1(config)#interface Serial0
R1(config-if)#no ip address
R1(config-if)#encapsulation frame-relay
R1(config)#interface Serial0.1 point-to-point
R1(config-subif)#ip address 10.1.1.1 255.255.255.0
R1(config-subif)#frame-relay interface-dlci 51
R1(config)#interface Serial0.2 point-to-point
R1(config-subif)#ip address 10.1.2.1 255.255.255.0
R1(config-subif)#frame-relay interface-dlci 52
R1(config)#router ospf 1
R1(config-router)#network 10.1.0.0 0.0.255.255 area 0
• OSPF considers each subinterface as a physical point-to-point network
• Adjacency is automatic
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Verifying OSPF Operation
Verifying OSPF Operation
© 2001, Cisco Systems, Inc. 5-46
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BSCI v1.2— 5-47© 2001, Cisco Systems, Inc.
Router#
show ip ospf interface
Verifying OSPF OperationVerifying OSPF Operation
• Displays area-ID and adjacency information
Router#
show ip protocols
• Verifies that OSPF is configuredRouter#
show ip route
• Displays all the routes learned by the router
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BSCI v1.2— 5-48© 2001, Cisco Systems, Inc.
• Displays OSPF timers and statistics
• Displays information about DR, BDR, and neighbors
• Displays the link-state database
Verifying OSPF Operation (cont.)Verifying OSPF Operation (cont.)
Router#
show ip ospf neighbor detail
Router#
show ip ospf database
Router#
show ip ospf
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BSCI v1.2— 5-49© 2001, Cisco Systems, Inc.
• Allows you to clear the IP routing table
Router#
clear ip route *
Router#
debug ip ospf option
• Displays router interaction during the hello, exchange, and flooding processes
Verifying OSPF Operation (cont.)Verifying OSPF Operation (cont.)
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BSCI v1.2— 5-50© 2001, Cisco Systems, Inc.
show ip ospf interfaceshow ip ospf interface
R2#sh ip ospf int e0Ethernet0 is up, line protocol is up
Internet Address 192.168.0.12/24, Area 0Process ID 1, Router ID 192.168.0.12, Network Type BROADCAST, Cost: 10Transmit Delay is 1 sec, State DROTHER, Priority 1Designated Router (ID) 192.168.0.11, Interface address 192.168.0.11Backup Designated router (ID) 192.168.0.13, Interface address 192.168.0.13Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in 00:00:04Neighbor Count is 3, Adjacent neighbor count is 2Adjacent with neighbor 192.168.0.13 (Backup Designated Router)Adjacent with neighbor 192.168.0.11 (Designated Router)
Suppress hello for 0 neighbor(s)
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BSCI v1.2— 5-51© 2001, Cisco Systems, Inc.
show ip ospf neighbor—Multiaccess and Point-to-Point
show ip ospf neighbor—Multiaccess and Point-to-Point
Neighbor ID Pri State Dead Time Address Interface192.168.0.13 1 2WAY/DROTHER 00:00:31 192.168.0.13 Ethernet0192.168.0.14 1 FULL/BDR 00:00:38 192.168.0.14 Ethernet0192.168.0.11 1 2WAY/DROTHER 00:00:36 192.168.0.11 Ethernet0192.168.0.12 1 FULL/DR 00:00:38 192.168.0.12 Ethernet0
OSPF over Ethernet—Multiaccess Network
Neighbor ID Pri State Dead Time Address Interface192.168.0.11 1 FULL/ - 00:00:39 10.1.1.2 Serial1
OSPF over HDLC—Point-to-Point Network
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BSCI v1.2— 5-52© 2001, Cisco Systems, Inc.
R2#show ip ospf database
OSPF Router with ID (192.168.0.12) (Process ID 1)
Router Link States (Area 0)
Link ID ADV Router Age Seq# Checksum Link count192.168.0.10 192.168.0.10 817 0x80000003 0xFF56 1192.168.0.11 192.168.0.11 817 0x80000003 0xFD55 1192.168.0.12 192.168.0.12 816 0x80000003 0xFB54 1192.168.0.13 192.168.0.13 816 0x80000003 0xF953 1192.168.0.14 192.168.0.14 817 0x80000003 0xD990 1
Net Link States (Area 0)
Link ID ADV Router Age Seq# Checksum192.168.0.14 192.168.0.14 812 0x80000002 0x4AC8
show ip ospf databaseshow ip ospf database
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BSCI v1.2— 5-53© 2001, Cisco Systems, Inc.
debug ip ospf adjdebug ip ospf adj
192.168.0.14 on Ethernet0, state 2WAYOSPF: end of Wait on interface Ethernet0OSPF: DR/BDR election on Ethernet0OSPF: Elect BDR 192.168.0.14OSPF: Elect DR 192.168.0.14
DR: 192.168.0.14 (Id) BDR: 192.168.0.14 (Id)OSPF: Send DBD to 192.168.0.14 on Ethernet0 seq 0x11DB opt 0x2 flag 0x7 len 32OSPF: Build router LSA for area 0, router ID 192.168.0.11OSPF: Neighbor change Event on interface Ethernet0OSPF: Rcv DBD from 192.168.0.14 on Ethernet0 seq 0x1598 opt 0x2 flag 0x7 len 32
state EXSTARTOSPF: NBR Negotiation Done. We are the SLAVEOSPF: Send DBD to 192.168.0.14 on Ethernet0 seq 0x1598 opt 0x2 flag 0x2 len 52OSPF: Rcv DBD from 192.168.0.14 on Ethernet0 seq 0x1599 opt 0x2 flag 0x3 len 92
state EXCHANGEOSPF: Exchange Done with 192.168.0.14 on Ethernet0OSPF: Send DBD to 192.168.0.14 on Ethernet0 seq 0x159A opt 0x2 flag 0x0 len 32OSPF: Synchronized with 192.168.0.14 on Ethernet0, state FULLOSPF: Build router LSA for area 0, router ID 192.168.0.11OSPF: Neighbor change Event on interface Ethernet0OSPF: DR/BDR election on Ethernet0OSPF: Elect BDR 192.168.0.13OSPF: Elect DR 192.168.0.14
DR: 192.168.0.14 (Id) BDR: 192.168.0.13 (Id)