Day+28+Slides+-+OSPF+(Part+3).pdf
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CCNA 200-301 Day 28 OSPF Part 3 Things we’ll cover OSPF network types OSPF neighbor/adjacency requirements OSPF LSA types Loopback Interfaces OSPF Area 0...
CCNA 200-301 Day 28 OSPF Part 3 Things we’ll cover OSPF network types OSPF neighbor/adjacency requirements OSPF LSA types Loopback Interfaces OSPF Area 0 A loopback interface is a virtual interface 172.16.1.0/28 192.168.2.0/24 in the router..14 G2/0 G2/0.254 It is always up/up (unless you manually G0/0 G0/0 shut it down) R1 R2.1.2 10.0.12.0/30 It is not dependent on a physical G1/0.1.1 G1/0 interface. 10.0.13.0/30 So, it provides a consistent IP address 10.0.24.0/30 that can be used to reach/identify the G0/0.2.2 G0/0 router..1 10.0.34.0/30.2 R3 R4 F2/0 F2/0 Dst: 10.0.13.1.126 G1/0 G1/0.254 192.168.3.0/25 192.168.4.0/24 Loopback Interfaces OSPF Area 0 A loopback interface is a virtual interface 172.16.1.0/28 192.168.2.0/24 in the router..14 G2/0 G2/0.254 It is always up/up (unless you manually G0/0 G0/0 shut it down) R1 R2.1.2 x 10.0.12.0/30 It is not dependent on a physical G1/0.1.1 G1/0 interface. 10.0.13.0/30 So, it provides a consistent IP address 10.0.24.0/30 that can be used to reach/identify the G0/0.2.2 G0/0 router..1 10.0.34.0/30.2 R3 x R4 F2/0 F2/0 Dst: 10.0.13.1.126 G1/0 G1/0.254 192.168.3.0/25 192.168.4.0/24 Loopback Interfaces OSPF Area 0 A loopback interface is a virtual interface 172.16.1.0/28 192.168.2.0/24 in the router..14 G2/0 L0: 1.1.1.1 G2/0.254 It is always up/up (unless you manually G0/0 G0/0 shut it down) R1 R2.1.2 x 10.0.12.0/30 It is not dependent on a physical G1/0.1.1 G1/0 interface. 10.0.13.0/30 So, it provides a consistent IP address 10.0.24.0/30 that can be used to reach/identify the G0/0.2.2 G0/0 router..1 10.0.34.0/30.2 R3 R4 F2/0 F2/0 Dst: 1.1.1.1.126 G1/0 G1/0.254 192.168.3.0/25 192.168.4.0/24 OSPF Network Types The OSPF ‘network type’ refers to the type of connection between OSPF neighbors (Ethernet, etc) There are three main OSPF network types: Broadcast -enabled by default on Ethernet and FDDI (Fiber Distributed Data Interface) interfaces Point-to-point -enabled by default on PPP (Point-to-Point Protocol) and HDLC (High-Level Data Link Control) interfaces Non-broadcast -enabled by default on Frame Relay and X.25 interfaces OSPF Broadcast Network Type OSPF Area 0 192.168.1.0/30 DR BDR DR DROther BDR DR.1.1.2 10.0.1.0/24.1 10.0.4.0/24 G0/0 192.168.2.0/29 G0/0 G1/0 G0/0 G1/0 G1/0.1.3 R1 R2 R4 DR.2.4 DR 10.0.3.0/24.1.1 10.0.5.0/24 G0/0 G0/0 G1/0 G1/0 DROther DR R3 R5 Enabled on Ethernet and FDDI interfaces by default. Routers dynamically discover neighbors by sending/listening for OSPF Hello messages using multicast address 224.0.0.5. A DR (designated router) and BDR (backup designated router) must be elected on each subnet (only DR if there are no OSPF neighbors, ie. R1’s G1/0 interface) Routers which aren’t the DR or BDR become a DROther. OSPF Broadcast Network Type OSPF Area 0 192.168.1.0/30 DR BDR DR DROther BDR DR.1.1.2 10.0.1.0/24.1 10.0.4.0/24 G0/0 192.168.2.0/29 G0/0 G1/0 G0/0 G1/0 G1/0.1.3 R1 R2 R4 DR.2.4 DR 10.0.3.0/24.1.1 10.0.5.0/24 G0/0 G0/0 G1/0 G1/0 DROther DR R3 R5 The DR/BDR election order of priority: 1: Highest OSPF interface priority 2: Highest OSPF Router ID ‘First place’ becomes the DR for the subnet, ‘second place’ becomes the BDR The default OSPF interface priority is 1 on all interfaces OSPF Broadcast Network Type OSPF Area 0 192.168.1.0/30 DR BDR DR DROther BDR DR.1.1.2 10.0.1.0/24.1 10.0.4.0/24 G0/0 192.168.2.0/29 G0/0 G1/0 G0/0 G1/0 G1/0.1.3 R1 R2 R4 DR.2.4 DR 10.0.3.0/24.1.1 10.0.5.0/24 G0/0 G0/0 G1/0 G1/0 DROther DR R3 R5 OSPF Broadcast Network Type OSPF Area 0 192.168.1.0/30 DR BDR DR DROther BDR DR.1.1.2 10.0.1.0/24.1 10.0.4.0/24 G0/0 192.168.2.0/29 G0/0 G1/0 G0/0 G1/0 G1/0.1.3 R1 R2 R4 DR.2.4 DR 10.0.3.0/24.1.1 10.0.5.0/24 G0/0 G0/0 G1/0 G1/0 DROther DR R3 R5 OSPF Broadcast Network Type OSPF Area 0 192.168.1.0/30 DR BDR DR DROther BDR DR.1.1.2 10.0.1.0/24.1 10.0.4.0/24 G0/0 192.168.2.0/29 G0/0 G1/0 G0/0 G1/0 G1/0.1.3 R1 R2 R4 DR.2.4 DR 10.0.3.0/24.1.1 10.0.5.0/24 G0/0 G0/0 G1/0 G1/0 DROther DR R3 R5 The DR/BDR election is ‘non-preemptive’. Once the DR/BDR are selected they will keep their role until OSPF is reset, the interface fails/is shut down, etc. If you set the OSPF interface priority to 0, the router CANNOT be the DR/BDR for the subnet. OSPF Broadcast Network Type OSPF Area 0 192.168.1.0/30 DR BDR DR BDR DR DR.1.1.2 10.0.1.0/24.1 10.0.4.0/24 G0/0 192.168.2.0/29 G0/0 G1/0 G0/0 G1/0 G1/0.1.3 R1 R2 R4 DR.2.4 DR 10.0.3.0/24.1.1 10.0.5.0/24 G0/0 G0/0 G1/0 G1/0 DROther DROther R3 R5 OSPF Broadcast Network Type OSPF Area 0 192.168.1.0/30 DR BDR DR BDR DR DR.1.1.2 10.0.1.0/24.1 10.0.4.0/24 G0/0 192.168.2.0/29 G0/0 G1/0 G0/0 G1/0 G1/0.1.3 R1 R2 R4 DR.2.4 DR 10.0.3.0/24.1.1 10.0.5.0/24 G0/0 G0/0 G1/0 G1/0 DROther DROther R3 R5 R4 became the DR, not R2. R2 became the BDR. → When the DR goes down, the BDR becomes the new DR. Then an election is held for the next BDR. R3 is a DROther, and is stable in the 2-way state. →DROthers (R3 and R5 in this subnet) will only move to the FULL state with the DR and BDR. The neighbor state with other DROthers will be 2-way. OSPF Broadcast Network Type OSPF Area 0 192.168.1.0/30 DR BDR DR BDR DR DR.1.1.2 10.0.1.0/24.1 10.0.4.0/24 G0/0 192.168.2.0/29 G0/0 G1/0 G0/0 G1/0 G1/0.1.3 R1 R2 R4 DR.2.4 DR 10.0.3.0/24.1.1 10.0.5.0/24 G0/0 G0/0 G1/0 G1/0 DROther DROther R3 R5 In the broadcast network type, routers will only form a full OSPF adjacency with the DR and BDR of the segment. Therefore, routers only exchange LSAs with the DR and BDR. DROthers will not exchange LSAs with each other. All routers will still have the same LSDB, but this reduces the amount of LSAs flooding the network. OSPF Broadcast Network Type OSPF Broadcast Network Type Messages to the DR/BDR are multicast using address 224.0.0.6 DR BDR OSPF Neighbors The DR and BDR will form a FULL adjacency with ALL routers in the subnet. Connection DROthers will between R1,R2 adjacency form a FULL comes up (oronly OSPF is activated) with the DR/BDR. Down State Init State Become Hello: RID 1.1.1.1, neighbor RID 0.0.0.0 neighbors 2-way State Hello: RID 2.2.2.2, neighbor RID 1.1.1.1 Hello: RID 1.1.1.1, neighbor RID 2.2.2.2 R2 R1 (DR/BDR ELECTION) RID: 1.1.1.1 Exstart State RID: 2.2.2.2 DBD Packets, Master/Slave determined Exchange Exchange State LSAs DBD Packets, describe content of LSDB (LSAs) Loading State LSR, LSU, LSAck (Share LSAs to synchronize LSDB) Full State OSPF Broadcast Network Type OSPF Area 0 192.168.1.0/30 DR BDR DR BDR DR DR.1.1.2 10.0.1.0/24.1 10.0.4.0/24 G0/0 192.168.2.0/29 G0/0 G1/0 G0/0 G1/0 G1/0.1.3 R1 R2 R4 DR.2.4 DR 10.0.3.0/24.1.1 10.0.5.0/24 G0/0 G0/0 G1/0 G1/0 DROther DROther R3 R5 OSPF Broadcast Network Type OSPF Point-to-Point Network Type OSPF Area 0 192.168.1.0/30 DR BDR DR DR.1.1 10.0.1.0/24.2 192.168.2.0/29 G0/0.1 10.0.4.0/24 G0/0 G1/0 S2/0 S2/0 G1/0.1.3 R1 R2 R4 DR.2.4 DR 10.0.3.0/24.1.1 10.0.5.0/24 G0/0 G0/0 G1/0 G1/0 DROther DROther R3 R5 Enabled on serial interfaces using the PPP or HDLC encapsulations by default. Routers dynamically discover neighbors by sending/listening for OSPF Hello messages using multicast address 224.0.0.5. A DR and BDR are not elected. These encapsulations are used for ‘point-to-point’ connections. Therefore there is no point in electing a DR and BDR. The two routers will form a Full adjacency with each other. Serial Interfaces Photo from: learnnetworkinglab.wordpress.com Serial Interfaces R1 192.168.1.0/30 R2.1 S2/0.2 S2/0 One side of a serial connection functions as DCE (Data Communications Equipment) The other side functions as DTE (Data Terminal Equipment) The DCE side needs to Ethernet interfaces use the speed command to configure specify the clock rate the interface’s operating speed. Serial interfaces use the (speed) of the connection clock rate command. Serial Interfaces R1 192.168.1.0/30 R2.1 S2/0.2 S2/0 The default encapsulation on a serial interface is HDLC. **actually cHDLC (Cisco HDLC) If you change the encapsulation, it must match on both ends or the interface will go down. Serial Interfaces R1 192.168.1.0/30 R2.1 S2/0.2 S2/0 The default encapsulation on a serial interface is HDLC. **actually cHDLC (Cisco HDLC) If you change the encapsulation, it must match on both ends or the interface will go down. Serial Interfaces R1 192.168.1.0/30 R2.1 S2/0.2 S2/0 Serial Interfaces R1 192.168.1.0/30 R2.1 S2/0.2 S2/0 Serial Interfaces The default encapsulation is HDLC. You can configure PPP encapsulation with this command: R1(config-if)# encapsulation ppp One side is DCE, one side is DTE. Identify which side is DCE/DTE: R1# show controllers interface-id You must configure the clock rate on the DCE side: R1(config-if)# clock rate bits-per-second OSPF Point-to-Point Network Type OSPF Area 0 192.168.1.0/30 DR BDR DR DR.1.1 10.0.1.0/24.2 192.168.2.0/29 G0/0.1 10.0.4.0/24 G0/0 G1/0 S2/0 S2/0 G1/0.1.3 R1 R2 R4 DR.2.4 DR 10.0.3.0/24.1.1 10.0.5.0/24 G0/0 G0/0 G1/0 G1/0 DROther DROther R3 R5 Configure the OSPF Network Type You can configure the OSPF network type on an interface with ip ospf network type For example, if two routers are directly connected with an Ethernet link, there is no need for a DR/BDR. You can configure the point-to-point network type in this case. NOTE: Not all network types work on all link types (for example, a serial link cannot use the broadcast network type) G0/0 G0/0 Configure the OSPF Network Type Broadcast Point-to-point Default on Ethernet, FDDI interfaces Default on HDLC, PPP (serial) interfaces DR/DBR elected No DR/BDR Neighbors dynamically discovered Neighbors dynamically discovered Default timers: Hello 10, Dead 40 Default timers: Hello 10, Dead 40 (Non-broadcast network type default timers = Hello 30, Dead 120) OSPF Neighbor Requirements 1) Area number must match OSPF Neighbor Requirements R1.1 192.168.1.0/30.2 R2 G0/0 G0/0 OSPF Neighbor Requirements R1.1 192.168.1.0/30.2 R2 G0/0 G0/0 OSPF Neighbor Requirements 1) Area number must match 2) Interfaces must be in the same subnet OSPF Neighbor Requirements R1 192.168.1.1/30 192.168.2.2/30 R2 G0/0 G0/0 OSPF Neighbor Requirements R1.1 192.168.1.0/30.2 R2 G0/0 G0/0 OSPF Neighbor Requirements 1) Area number must match 2) Interfaces must be in the same subnet 3) OSPF process must not be shutdown OSPF Neighbor Requirements R1.1 192.168.1.0/30.2 R2 G0/0 G0/0 OSPF Neighbor Requirements 1) Area number must match 2) Interfaces must be in the same subnet 3) OSPF process must not be shutdown 4) OSPF Router IDs must be unique OSPF Neighbor Requirements R1.1 192.168.1.0/30.2 R2 G0/0 G0/0 OSPF Neighbor Requirements 1) Area number must match 2) Interfaces must be in the same subnet 3) OSPF process must not be shutdown 4) OSPF Router IDs must be unique 5) Hello and Dead timers must match OSPF Neighbor Requirements R1.1 192.168.1.0/30.2 R2 G0/0 G0/0 OSPF Neighbor Requirements 1) Area number must match 2) Interfaces must be in the same subnet 3) OSPF process must not be shutdown 4) OSPF Router IDs must be unique 5) Hello and Dead timers must match 6) Authentication settings must match OSPF Neighbor Requirements R1.1 192.168.1.0/30.2 R2 G0/0 G0/0 OSPF Neighbor Requirements 1) Area number must match 2) Interfaces must be in the same subnet 3) OSPF process must not be shutdown 4) OSPF Router IDs must be unique 5) Hello and Dead timers must match 6) Authentication settings must match 7) IP MTU settings must match Can become OSPF neighbors, but OSPF doesn’t operate properly. OSPF Neighbor Requirements R1.1 192.168.1.0/30.2 R2 G0/0 G0/0 OSPF Neighbor Requirements 1) Area number must match 2) Interfaces must be in the same subnet 3) OSPF process must not be shutdown 4) OSPF Router IDs must be unique 5) Hello and Dead timers must match 6) Authentication settings must match 7) IP MTU settings must match Can become OSPF neighbors, but OSPF doesn’t operate properly. 8) OSPF Network Type must match OSPF Neighbor Requirements R1.1 192.168.1.0/30.2 R2 G0/0 G0/0 OSPF Neighbor Requirements R1.1 192.168.1.0/30.2 R2 G0/0 G0/0 OSPF Neighbor Requirements 1) Area number must match 2) Interfaces must be in the same subnet 3) OSPF process must not be shutdown 4) OSPF Router IDs must be unique 5) Hello and Dead timers must match 6) Authentication settings must match 7) IP MTU settings must match Can become OSPF neighbors, but OSPF doesn’t operate properly. 8) OSPF Network Type must match. OSPF LSA Types OSPF Area 0 192.168.1.0/30 DR 203.0.113.0/30 DR BDR.1.1 G0/0.2 10.0.1.0/24.2 192.168.2.0/29.1 G0/0 G1/0 S2/0 S2/0.3 G1/0.1 R1 R2 R4 DR.2.4 DR 10.0.3.0/24.1.1 10.0.5.0/24 G0/0 G0/0 G1/0 G1/0 DROther DROther R3 R5 The OSPF LSDB is made up of LSAs. There are 11 types of LSA, but there are only 3 you should be aware of for the CCNA: Type 1 (Router LSA) Type 2 (Network LSA) Type 5 (AS External LSA) OSPF LSA Types Type 1 (Router LSA) -Every OSPF router generates this type of LSA. -It identifies the router using its router ID. -It also lists networks attached to the router’s OSPF-activated interfaces. Type 2 (Network LSA) -Generated by the DR of each ‘multi-access’ network (ie. the broadcast network type). -Lists the routers which are attached to the multi-access network. Type 5 (AS-External LSA) -Generated by ASBRs to describe routes to destinations outside of the AS (OSPF domain). OSPF LSA Types Things we covered OSPF network types OSPF neighbor/adjacency requirements OSPF LSA types Quiz 1 Which option states a characteristic of the OSPF point-to-point network type that is different than the OSPF broadcast network type? a) DR/BDR elections are held. b) DR/BDR elections are not held. c) Neighbors are dynamically discovered. d) Neighbors are not dynamically discovered. Quiz 2 There is an OSPF broadcast network with 5 connected routers. R1 is the DR on its G0/0 interface. How many FULL OSPF adjacencies does R1 have on the interface? a) 1, with the BDR. b) 2, with the DR and BDR. c) 4, with all neighbors. d) 5, with all routers connected to the segment. Quiz 3 Which of the following are requirements for routers to become OSPF neighbors? (select two) a) Hello and Dead timers must match b) OSPF Process IDs must match c) OSPF Router IDs must match d) Interfaces must be in the same area e) Interfaces must be in different areas f) Interfaces must be in different subnets Quiz 4 Which of the following OSPF LSA types is generated only by the DR of a multi-access network, such as the broadcast network type? a) Type 1 b) Type 2 c) Type 3 d) Type 5 Quiz 5 R1 is connected to an OSPF Broadcast network on its G0/0 interface. R4 is the DR of the segment and R3 is the BDR. All routers on the segment have the default OSPF priority. You issue the ip ospf priority 100 command on R1’s G0/0 to make it the DR. Which of the following statements are true about the network after you issue the command? (Select two) a) R1 is the DR. b) R1 is the BDR. c) R1 is still a DROther because its priority isn’t high enough. d) If you issue the clear ip ospf process command on R4, R1 will become the BDR. e) If you issue the clear ip ospf process command on R4, R1 will become the DR. f) The DR and BDR of the network are unchanged. Supplementary Materials Review flash cards (link in the description) Packet Tracer lab JCNP-Level Channel Members *as of August 23rd, 2020
