Quick Answer: How Does OSPF Check Reference Bandwidth?

What is OSPF priority?

Use the ip ospf priority command to set the router priority, which determines the designated router for this network.

When two routers are attached to a network, both attempt to become the designated router.

A router with a router priority set to zero cannot become the designated router or backup designated router..

What is reference bandwidth in OSPF?

OSPF uses a simple formula to calculate the OSPF cost for an interface with this formula: cost = reference bandwidth / interface bandwidth. The reference bandwidth is a value in Mbps that we can set ourselves. By default this is 100Mbps on Cisco IOS routers. The interface bandwidth is something we can lookup.

How do you set auto cost reference bandwidth?

To adjust the reference bandwidth, use the auto-cost reference-bandwidth Mb/s router configuration command. This command must be configured on every router in the OSPF domain. Notice that the value is expressed in Mb/s; therefore, to adjust the costs for: Gigabit Ethernet – auto-cost reference-bandwidth 1000.

How is OSPF calculated?

Open Shortest Path First (OSPF) uses “Cost” as the value of metric and uses a Reference Bandwidth of 100 Mbps for cost calculation. The formula to calculate the cost is Reference Bandwidth divided by interface bandwidth. For example, in the case of 10 Mbps Ethernet , OSPF Metric Cost value is 100 Mbps / 10 Mbps = 10.

Does OSPF use hop count?

With RIP, a destination that requires more than 15 consecutive hops is considered unreachable, and this limitation inhibits the maximum size of a network. OSPF has no hop limitation. You can add as many routers to a network as you want.

What is the default cost of OSPF?

Syntax Descriptionarea-idIdentifier for the OSPF area where you want to configure the default cost. The area ID can be from 0 to 4294967295 or an IP address.costCost for the default summary route used for a stub or NSSA. The range is from 0 to 16777215.

Why we use OSPF?

The main advantage of a link state routing protocol like OSPF is that the complete knowledge of topology allows routers to calculate routes that satisfy particular criteria. This can be useful for traffic engineering purposes, where routes can be constrained to meet particular quality of service requirements.

How do you modify the reference bandwidth with OSPFv3?

For example, to change the reference bandwidth to 500, enter the following command. The reference bandwidth specified in this example results in the following costs: 10 Mbps port cost = 500/10 = 50. 100 Mbps port cost = 500/100 = 5.

How is OSPF cost set?

To explicitly specify the cost of an interface, issue the ip ospf cost command in interface configuration mode. To control how OSPF calculates the default metrics for the interface (based on the reference bandwidth), issue the auto-cost command in OSPF router configuration mode.

How do I change bandwidth in OSPF?

To change the reference bandwidth, enter a command such as the following at the OSPF configuration level of the CLI….Changing the reference bandwidth10 Mbps port’s cost = 500/10 = 50.100 Mbps port’s cost = 500/100 = 5.1000 Mbps port’s cost = 500/1000 = 0.5, which is rounded up to 1.

Why would you want to change the OSPF default reference bandwidth?

Why would you want to change the OSPF default reference-bandwidth? You would change the OSPF default reference-bandwidth to make a route have more or less cost. … 23.0/30 networks from R1 are higher due to changing the route cost.

How does OSPF calculate best path?

External Type-2 routes. If there are multiple routes to a network with the same route type, the OSPF metric calculated as cost based on the bandwidth is used for selecting the best route. The route with the lowest value for cost is chosen as the best route.

What is default information originate?

default-information originate (OSPF) To generate a default external route into an Open Shortest Path First (OSPF) routing domain, use the default-information originate command. To disable this feature, use the no form of this command.