https://lms.onnocenter.or.id/wiki/index.php?action=history&feed=atom&title=IPv6%3A_OSPF_CostIPv6: OSPF Cost - Revision history2026-04-25T23:29:38ZRevision history for this page on the wikiMediaWiki 1.45.1https://lms.onnocenter.or.id/wiki/index.php?title=IPv6:_OSPF_Cost&diff=56107&oldid=prevOnnowpurbo: Created page with "Cost OSPF uses a reference bandwidth of 100 Mbps (10^8) for cost calculation. The formula to calculate the cost is reference bandwidth divided by interface bandwidth ; Interf..."2019-04-05T21:15:23Z<p>Created page with "Cost OSPF uses a reference bandwidth of 100 Mbps (10^8) for cost calculation. The formula to calculate the cost is reference bandwidth divided by interface bandwidth ; Interf..."</p>
<p><b>New page</b></p><div>Cost<br />
<br />
OSPF uses a reference bandwidth of 100 Mbps (10^8) for cost calculation. The formula to calculate the cost is reference bandwidth divided by interface bandwidth ; Interface Cost= 10^8/(interface bandwidth). Calculated values are rounded up to the nearest single decimal value. This means that OSPF will calculate interfaces with speeds higher than 10 Mbps as a cost of 1 (Table 1). T he result of this is that OSPF routers in the network cannot make an accurate path calculation when comparing fast Ethernet interface versus a gigabit Ethernet interface as both interfaces has a cost of 1. [2]<br />
Interface Type Cost<br />
100 Gbps 1<br />
40 Gbps 1<br />
10 Gbps 1<br />
10 Gbps 1<br />
1 Gbps 1<br />
100 Mbps 1<br />
10 Mbps 10<br />
1.544 Mbps 64<br />
768 Kbps 133<br />
384 Kbps 266<br />
128 Kbps 781<br />
<br />
Table 1 - Default OSPF cost calculations.<br />
<br />
There are two methods for changing the calculated costs - auto-cost and interface cost.<br />
<br />
The auto-cost reference-bandwidth command allows you to change the reference bandwidth that OSPF uses to calculate its metrics:<br />
<br />
router ospf 1<br />
... <br />
auto-cost reference-bandwidth 1000000<br />
<br />
REMEMBER You must ensure the reference bandwidth is consistent across all routers.<br />
<br />
ip ospf cost can also be used to change the OSPF cost. However, this works on a per-interface basis and will override the calculated cost.<br />
<br />
int gi0/1<br />
...<br />
ip ospf cost 1234<br />
<br />
To verify the interface cost, the following command is used:<br />
<br />
show ip ospf interface | inc Cost<br />
Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 1<br />
Topology-MTID Cost Disabled Shutdown Topology Name<br />
Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 1<br />
Topology-MTID Cost Disabled Shutdown Topology Name</div>Onnowpurbo