Where is OSPF reference bandwidth?
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.
What is the OSPF default reference bandwidth?
100Mbps
The reference bandwidth is a value in Mbps that we can set ourselves. By default this is 100Mbps on Cisco IOS routers.
What default reference bandwidth does OSPF use when calculating the metric?
100 Mbps
The default reference bandwidth of 100 Mbps is used for OSPF cost calculation.
How is auto cost reference bandwidth calculated?
The reference bandwidth specified in this example results in the following costs:
- 10 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.
- 155 Mbps port cost = 500/155 = 3.23, which is rounded up to 4.
What is bandwidth command in Cisco router?
The bandwidth command sets an informational parameter to communicate the current bandwidth to the higher-level protocols. IGRP uses the minimum path bandwidth to determine a routing metric. The TCP protocol adjusts initial retransmission parameters based on the apparent bandwidth of the outgoing interface.
Why would you want to change the OSPF default reference bandwidth?
By default, the reference bandwidth is 100 Mbps. However, if you have faster links in your network, such as gigabit Ethernet or OC-3 connections, OSPF can’t give these links a better cost than 1. So you should set the reference bandwidth to at least as high as the fastest link in your network.
What is auto cost reference bandwidth?
OSPF calculates the cost of a route as the ratio of the reference bandwidth to the bandwidth of the egress interface. An increase in the reference bandwidth results in an increased cost. If the resulting cost is less than 1, the software rounds the cost up to 1.
How do I configure 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.
What is the OSPF cost for a T 1 link bandwidth 1.544 Mbps given the reference bandwidth of 100mbps?
We divide 100 by 100 and that gives us a cost of 1. On a serial interface, like a T1 in that example here, the bandwidth is 1.544 Mbps. That will default to a cost of 64 because a hundred divided by 1.544 is 64.
How do I check the bandwidth of my router?
How to Monitor Bandwidth Usage on Your Wireless Router
- Log into your wireless router’s configuration utility.
- Open the “Advanced” section, then click the “Traffic Meter,” “Bandwidth Usage,” “Network Monitor” or other similarly named link.
What is the purpose of the bandwidth command?
How do I advertise a loopback in OSPF?
Unlike RIP/EIGRP, OSPF has a special way to advertise loopback interfaces. In OSPF, the route information of the loopback interface is advertised as the host route with subnet mask /32. For example, configure IP address 10.0. 0.2/24 for Loopback0 on R2 in the following figure, and advertise it with OSPF.
What is the best reference bandwidth for OSPF?
The default reference bandwidth used to calculate the OSPF metric can be changed to reflect today’s modern networks in which case a 100Gbps reference bandwidth is a good estimate or perhaps you wish to future proof your network as many corporations do and use a reference bandwidth of 1Tbps.
When should I use the distance OSPF command?
A common reason to use the distance ospf command is when you have multiple OSPF processes with mutual redistribution, and you want to prefer internal routes from one over external routes from the other. Release 12.2 (33)SRB
What is the OSPF command in Cisco IOS?
This command was introduced. This command was integrated into Cisco IOS XE Release 3.4S. You must configure the router ospf command before you can configure the fast-reroute tie-break command. You can use the show ip ospf fast-reroute command to display the default, or the current, tiebreak configuration.
What is the default reference BW for OSPF?
The default reference BW is 100 Mbps. So with default BW Ref value all links with speed > = 100 Mbps are considered equal with OSPF cost 1. This is also the reason for changing the reference value.