Please enable JavaScript.
Coggle requires JavaScript to display documents.
Module 2: Single-Area OSPFv2 Configuration :tada:, image, image, image,…
Module 2: Single-Area OSPFv2 Configuration :tada:
2.1 Router ID de OSPF
2.1.1 OSPF Reference Topology
There is currently no static routing or dynamic routing configured on any of the routers. All interfaces on R1, R2, and R3 (except the loopback 1 on R2) are within the OSPF backbone area. The ISP router is used as the gateway to the internet of the routing domain.
the loopback interface is used to simulate the WAN link to the Internet and a LAN connected to each router. This is done to allow this topology to be duplicated for demonstration purposes on routers that only have two Gigabit Ethernet interfaces.
2.4. Modificación de OSPFv2 de área única
2.4.2 Adjust the Reference Bandwidth
The OSPF cost is always an integer. For networks with high-speed links (greater than 100 Mbps), the reference bandwidth should be increased using auto-cost reference-bandwidth to ensure consistency across all routers.
2.4.3 OSPF Accumulates Costs
The total route cost is the sum of the costs of each link. Loopback interfaces have a default cost of 1.
2.4.4 Manually Set OSPF Cost Value
The cost can be manually adjusted on specific interfaces using ip ospf cost, influencing the path chosen by OSPF.
2.4.1 Cisco OSPF Cost Metric
OSPF uses cost as a metric to determine the best route, based on the link’s bandwidth. The formula is:
Cost = 100,000,000 bps / interface bandwidth (bps)
It can be manually adjusted using ip ospf cost or by modifying the reference bandwidth with auto-cost reference-bandwidth.
2.4.7 Hello Packet Intervals
OSPFv2 Hello packets are sent every 10 seconds to 224.0.0.5. The Dead interval is 40 seconds and determines the time before declaring a neighbor inactive.
2.4.8 Verify Hello and Dead Intervals
These intervals can be checked with show ip ospf interface to ensure stable communication between routers.
2.4.9 Modify OSPFv2 Intervals
Hello and Dead intervals can be adjusted to improve convergence using ip ospf hello-interval and ip ospf dead-interval.
2.4.10 Syntax Checker - Modifying Hello and Dead Intervals on R3
A practical test to modify and verify OSPF intervals on a router.
2.4.5 Test Failover to Backup Route
When a link fails, OSPF recalculates routes and redirects traffic. Failover can be tested by disabling an interface (shutdown) and verifying the routing table.
2.1.2 Router Configuration Mode for OSPF
OSPFv2 is enabled using the router ospf process-id global configuration mode command,The process-id value represents a number between 1 and 65,535.
for tha value does not have to be the same value on the other OSPF routers to establish adjacencies.
After entering the router ospf process-id command,the R1(config-router)# prompt. Enter a question mark (?), to view all the commands available in this mode
2.1.3 Router IDs
OSPF domain. The router ID can be defined by an administrator or automatically assigned by the router. The router ID is used by an OSPF-enabled router
Participate in the synchronization of OSPF databases - During the Exchange State, the router with the highest router ID will send their database descriptor (DBD) packets first.
Participate in the election of the designated router (DR) - In a multiaccess LAN environment, the router with the highest router ID is elected the DR. Router ID is elected the backup designated router (BDR).
2.1.4 Orden de prioridad del router ID
1.The router ID is explicitly configured using the OSPF router-id rid router configuration mode command. The rid value is any 32-bit value expressed as an IPv4 address.
2.If the router ID is not explicitly configured, the router chooses the highest IPv4 address of any of configured loopback interfaces. This is the next best alternative to assigning a router ID.
3.If no loopback interfaces are configured, then the router chooses the highest active IPv4 address of any of its physical interfaces. This is the least recommended method
2.1.5 Configure a Loopback Interface as the Router ID
In the reference topology, only the physical interfaces are configured and active. The loopback interfaces have not been configured. When OSPF routing is enabled on the router, the routers would pick the following highest active configured IPv4 address as the router ID.
R1: 10.1.1.14 (G0/0/1)
R2: 10.1.1.9 (G0/0/1)
R3: 10.1.1.13 (G0/0/0)
2.1.6 Explicitly Configure a Router ID
has been updated to show the router ID for each router
R1 uses router ID 1.1.1.1
R2 uses router ID 2.2.2.2
R3 uses router ID 3.3.3.3
2.1.7 Modify a Router ID
After a router selects a Router ID in OSPF, it will not change unless the router is restarted or the OSPF process is reset. If the configured Router ID is removed, as in the case of R1, the router will select a new address (such as 10.10.1.1 in the example), which corresponds to its Loopback 0 interface. To manually configure the Router ID, the router-id command is used.
If the Router ID is changed, as in the case of R1, it is necessary to reset the OSPF process so that adjacencies with other routers are renegotiated with the new ID. This is done using the clear ip ospf process command. The preferred method to update the Router ID is to clear the OSPF process. Afterward, the change can be verified using the show ip protocols command.
2.1.8 Syntax Checker - Configure R2 and R3 Router IDs
2.6 Verify single-Area OSPFv2
Commands for determinig that OSFP is operating as expected
show ip ospf neighbor: Verify that the router has formed an adjacency with its neighboring routers
show ip protocols: Quickest way to verify vital OSPF configuration information
show ip ospf: Used to examine the OSPFv2 process ID and router ID, as shown in the following command output. This command displays the OSPFv2 area information and the last time the SPF algorithm was executed.
show ip ospf interface: Provides a detailed list for every OSPFv2-enabled interface.
OSPFv2 Reference Topology
2.2 Redes de punto a punto OSPF
2.2.1 The network Command Syntax
configure OSPF directly on the interface with the ip ospf command,se utilizan para determinar qué interfaces participan en el proceso de enrutamiento para un área OSPFv2
The network-address wildcard-mask syntax is used to enable OSPF on interfaces. Any interfaces on a router that match the network address in the network command are enabled to send and receive OSPF packets.
The area area-id syntax refers to the OSPF area. When configuring single-area OSPFv2, the network command must be configured with the same area-id value on all routers. Although any area ID can be used, it is good practice to use an area ID of 0 with single-area OSPFv2. This convention makes it easier if the network is later altered to support multiarea OSPFv2.
2.2.2 El Wildcard Mask
In a subnet mask, binary 1 is equal to a match and binary 0 is not a match
1.Wildcard mask bit 0 - coincide con el valor de bit correspondiente en la dirección.
2.Wildcard mask bit 1 - omite el valor del bit correspondiente en la dirección
The easiest method for calculating a wildcard mask is to subtract the network subnet mask from 255.255.255.255, as shown for /24 and /26 subnet masks
2.2.4 Configure OSPF Using the network Command
l wildcard mask identifies the interface based on network addresses. Any active interface configured with an IPv4 address belonging to that network will participate in the OSPFv2 routing process.
!
image
the second example shows how OSPFv2 can be enabled by specifying the exact IPv4 address of the interface using a quadruple zero wildcard mask. Enter network 10.1.1.5 0.0.0.0 area 0 R1 tells the router to enable the Gigabit Ethernet 0/0/0 interface for the routing process. As a result, the OSPFv2 process announces the network that is on this interface (10.1.1.4/30).
2.2.6 Configure OSPF Using the ip ospf Command
use the ip ospf interface configuration mode command.
Para R1, elimine los comandos de red mediante el uso de la no forma de los network comandos. Y luego vaya a cada interfaz y configure el ip ospf comando, como se muestra en la ventana de comandos.
2.3. Multiaccess OSPF Networks
2.3.1 OSPF Network Type
Another type of network that uses OSPF is the multiaccess OSPF network. Multiaccess OSPF networks are unique in that one router controls the distribution of LSAs. The router that is elected for this role should be determined by the network administrator through proper configuration.
2.3.3 OSPF Multiaccess Reference Topology
In the multiaccess topology shown in the figure, there are three routers interconnected over a common Ethernet multiaccess network, 192.168.1.0/24. Each router is configured with the indicated IPv4 address on the Gigabit Ethernet 0/0/0 interface.
2.3.4 Verify OSPF Router Roles
2.3.2 OSPF Designated Router
The DR is responsible for collecting and distributing LSAs sent and received. The DR uses the multicast IPv4 address 224.0.0.5 which is meant for all OSPF routers.
A BDR is also elected in case the DR fails. The BDR listens passively and maintains a relationship with all the routers.
2.3.5 Verify DR/BDR Adjacencies
FULL/DROTHER - This is a DR or BDR router that is fully adjacent with a non-DR or BDR router. These two neighbors can exchange Hello packets, updates, queries, replies, and acknowledgments.
FULL/DR - The router is fully adjacent with the indicated DR neighbor. These two neighbors can exchange Hello packets, updates, queries, replies, and acknowledgments.
FULL/BDR - The router is fully adjacent with the indicated BDR neighbor. These two neighbors can exchange Hello packets, updates, queries, replies, and acknowledgments.
2-WAY/DROTHER - The non-DR or BDR router has a neighbor relationship with another non-DR or BDR router. These two neighbors exchange Hello packets.
2.3.6 Default DR/BDR Election Process
The routers in the network elect the router with the highest interface priority as the DR. The router with the second highest interface priority is elected as the BDR.
If the interface priorities are equal, then the router with the highest router ID is elected the DR. The router with the second highest router ID is the BDR.
2.3.7 DR Failure and Recovery
After the DR is elected, it remains the DR until one of the following events occurs:
The DR fails.
The OSPF process on the DR fails or is stopped.
The multiaccess interface on the DR fails or is shutdown.
2.3.8 The ip ospf priority Command
If the interface priorities are equal on all routers, the router with the highest router ID is elected the DR. It is possible to configure the router ID to manipulate the DR/BDR election. However, this process only works if there is a stringent plan for setting the router ID on all routers.
2.3.9 Configure OSPF Priority
2.3.10 Syntax Checker - Configure OSPF Priority
2.5. Default Route Propagation
2.5.1 Propagate a Default Static Route in OSPFv2
Your network users will need to send packets out of your network to non-OSPF networks, such as the internet.
2.5.2 Verify the Propagated Default Route
