ospf cost...

cisco defines ospf cost as the inverse of bandwidth, whatever that means...
here is a great link from train signal, however, it doesn't explore cost as the inverse of bandwidth, it simply describes how to configure cost...

http://www.trainsignal.com/blog/cisco-ccnp-ospf

As already mentioned, the OSPF process assigns cost values to interfaces based on the inverse of the bandwidth parameter assigned to the interface with the bandwidth command.
For calculating the SPF to a given destination, the router takes into consideration the costs of the links along various paths. The path with the lower cost is selected as the shortest path.

from:  http://www.cisco.com/en/US/tech/tk365/technologies_q_and_a_item09186a0080094704.shtml#q3

Q. How does OSPF calculate its metric or cost?

A. OSPF 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 Ethernet, it is 100 Mbps / 10 Mbps = 10.

Note: If ip ospf cost cost is used on the interface, it overrides this formulated cost. For more information, refer to OSPF Cost.
 

from:  http://www.cisco.com/en/US/tech/tk365/technologies_white_paper09186a0080094e9e.shtml#t6

OSPF Cost

The cost (also called metric) of an interface in OSPF is an indication of the overhead required to send packets across a certain interface. The cost of an interface is inversely proportional to the bandwidth of that interface. A higher bandwidth indicates a lower cost. There is more overhead (higher cost) and time delays involved in crossing a 56k serial line than crossing a 10M ethernet line. The formula used to calculate the cost is:

• cost= 10000 0000/bandwith in bps
  
  

and from scott morris, the simple answer:

So "auto-cost reference-bandwidth 100" is the default where 100M links = 1.

So for 1G link to equal 1, the auto-cost would be 1000.  For 10G, it would be 10000, for 100G, it would be 100000.

bandwidth v throughput

my day today is full of conflict... the excitement never ends...

bandwidth is the theoretical potential a device has for transmitting based on some measured guideline.. for instance, fastethernet can have a a maximum data rate of 100mbs but you'll probably never see that happen...

throughput is the actual amount of data being transported at a given moment in time...

according to dictionary.com  

 Bandwidth:
A data transmission rate; the maximum amount of information (bits/second) that can be transmitted along a channel

Throughput:
The amount of data transferred in one direction over a link divided by the time taken to transfer it, usually expressed in bits or bytes per second. 

and mark this from

 http://learn-networking.com/network-design/a-guide-to-bandwidth-and-throughput

The Difference between Throughput and Bandwidth

Although bandwidth can tell us about how much information a network can move at a period of time, you’ll find that actual network speeds are much lower. We use the term throughput to refer to the actual bandwidth that is available to a network, as opposed to theoretical bandwidth.

Several different things may affect the actual bandwidth a device gets. The number of users accessing the network, the physical media, the network topology, hardware capability, and many other aspects can affect bandwidth.
To calculate data transfer speeds, we use the equation Time = Size / Theoretical Bandwidth.

Keep in mind that the above equation is actually what we use to find the “best download.” It assumes optimal network speeds and conditions since we use theoretical bandwidth. So to get a better idea on the typical download speed, we use a different equation: Time = Size / Actual Throughput.

lance link secret chimp...

link state/status...

every router learns about it's own link states and the state of its directly connected networks... it determines this by link UP status and ip address

every router forms adjacencies with its neighbor on directly connected networks via hello packets

every router builds a link state packet declaring the state of  each directly connected link and forwards it to its neighbor.  this lsp includes, bandwidth, neighbor id and link type

upon receipt, every router floods it's OWN neighbors with this lsp, and so on.  every router stores a copy of its neighbor's lsp's in its database


every router then constructs its OWN view of the topology and best path determination using the SPF algorithm.  a common tree is created, however, it has been defined independently by each router

linkage

bandaid 64...

if you want to determine your own successor routes in eigrp...

r2620_03(config-if)#int fa0/0
r2620_03(config-if)#bandw 1
r2620_03(config-if)#int s0/0
r2620_03(config-if)#bandw 64
r2620_03(config-if)#do sh ip route eigrp
     172.16.0.0/16 is variably subnetted, 5 subnets, 3 masks
D       172.16.3.2/32
           [90/2560514560] via 192.168.100.2, 00:00:58, FastEthernet0/0
D       172.16.1.0/24 [90/5152000] via 192.168.10.9, 00:00:49, Serial0/0
D       172.16.3.1/32 [90/5024000] via 192.168.10.9, 00:00:49, Serial0/0
D       172.16.2.0/24 [90/4640000] via 192.168.10.9, 00:00:49, Serial0/0
D       172.16.3.0/30 [90/5024000] via 192.168.10.9, 00:00:49, Serial0/0

r2620_03(config-if)#int fa0/0
r2620_03(config-if)#bandw 64
r2620_03(config-if)#int s0/0
r2620_03(config-if)#band 1
r2620_03(config-if)#do sh ip route eigrp
     172.16.0.0/16 is variably subnetted, 5 subnets, 3 masks
D       172.16.3.2/32
           [90/40514560] via 192.168.100.2, 00:00:13, FastEthernet0/0
D       172.16.1.0/24
           [90/40130560] via 192.168.100.2, 00:00:01, FastEthernet0/0
D       172.16.3.1/32 [90/2561024000] via 192.168.10.9, 00:00:01, Serial0/0
D       172.16.2.0/24
           [90/40642560] via 192.168.100.2, 00:00:01, FastEthernet0/0
D       172.16.3.0/30
           [90/40514560] via 192.168.100.2, 00:00:01, FastEthernet0/0
r2620_03(config-if)#

the master of your successor...

below will redistribute a static route... notice the code and the AD...

r2620_01#config t
Enter configuration commands, one per line.  End with CNTL/Z.
r2620_01(config)#ip route 0.0.0.0 0.0.0.0 lo0
r2620_01(config)#router eigrp 1
r2620_01(config-router)#redistribute static
r2620_01(config-router)#

r2620_03#sh ip route eigrp
     172.16.0.0/16 is variably subnetted, 5 subnets, 3 masks
D       172.16.3.2/32
           [90/40514560] via 192.168.100.2, 00:13:08, FastEthernet0/0
D       172.16.1.0/24
           [90/40130560] via 192.168.100.2, 00:12:56, FastEthernet0/0
D       172.16.3.1/32 [90/2561024000] via 192.168.10.9, 00:12:56, Serial0/0
D       172.16.2.0/24
           [90/40642560] via 192.168.100.2, 00:12:56, FastEthernet0/0
D       172.16.3.0/30
           [90/40514560] via 192.168.100.2, 00:12:56, FastEthernet0/0
D*EX 0.0.0.0/0 [170/2560640000] via 192.168.10.9, 00:00:53, Serial0/0
r2620_03#