OSPF vs EIGRP calculation?

---

Quick question after going back and re-watching the OSPF and EIGRP episodes in the CCNA Routing and Switching lineup. So to compare the two:

OSPF
(Dijkstra's algorithm)
Reference bandwidth / actual bandwidth = COST
Reference bandwidth is 100 Mbps or 100,000,000 bits.

EIGRP
( Diffusing Update Algorithm - DUAL)
Reference bandwidth / actual bandwidth * 256 = (Feasible Distance?)
Reference bandwidth is 10 Mbps or 10,000,000

What wasn't clear in each episode was the metric used for "actual bandwidth" in each calculation/formula. In the OSPF episode it appeared that the "actual bandwidth" was measured in bits for the purposes of the calculation whereas in the DUAL algorithm the "actual bandwidth" was measured in Kilobits per second or Kbps.

So a T1 for example would be 1,544 if you were doing EIGRP and 1,544,000 if you were doing the OSPF calculation. Am I correct here?

One follow up question for the purpose of the exam.. The result of the OSPF calculation is called "Cost", but what is the result of the EIGRP calculation called? Feasible Distance?

Regards,
Adam Tyler

@Adam-Tyler said in OSPF vs EIGRP calculation?:

Quick question after going back and re-watching the OSPF and EIGRP episodes in the CCNA Routing and Switching lineup. So to compare the two:

OSPF
(Dijkstra's algorithm)
Reference bandwidth / actual bandwidth = COST
Reference bandwidth is 100 Mbps or 100,000,000 bits.

EIGRP
( Diffusing Update Algorithm - DUAL)
Reference bandwidth / actual bandwidth * 256 = (Feasible Distance?)
Reference bandwidth is 10 Mbps or 10,000,000

What wasn't clear in each episode was the metric used for "actual bandwidth" in each calculation/formula. In the OSPF episode it appeared that the "actual bandwidth" was measured in bits for the purposes of the calculation whereas in the DUAL algorithm the "actual bandwidth" was measured in Kilobits per second or Kbps.

So a T1 for example would be 1,544 if you were doing EIGRP and 1,544,000 if you were doing the OSPF calculation. Am I correct here?

Yes. The actual bandwidth is dependent upon the type of connection many times.

When doing a comparison for the metrics between OSPF and EIGRP. OSPF takes the lowest bandwidth path to the destination determined by
Actual bandwidth on a link/ 100Mbps (100,000,000 bps)

If using EIGRP, the metric is determined by bandwidth and delay--composite metric.
On each link you must determine by:
(10000000/actual bandwidth in kbps) + Delay in TENS of mircoseconds X 256

One follow up question for the purpose of the exam.. The result of the OSPF calculation is called "Cost", but what is the result of the EIGRP calculation called? Feasible Distance?

The FD is the result of the calculation but that is only help determine the Successor and Feasible Successors.

Please let me know if I'm not answering the actual question you asked.

Regards,
Adam Tyler

Thanks Ronnie, I think you answered my question. Use bits per second for OSPF and kilobits per second for EIGRP... Thanks.

Regards,
Adam Tyler