hi all,
I am working through the INE WB1 and (due to confusing myself) had to go away and do more examples to try understand the way that the metric/cost is made up.
I think I have a "technique" for working out how the metric comes to the values that "sh ip route 150.1.9.0" shows; knowing the metric/cost is not enough, I need to know *how* it's made up...
So here goes. I would like to know if my technique works or is just absolute luck that the figure match up.
Calculating when going from SW4 to 150.1.9.0 (loopback network on SW3); ignore the actual values - I'm using IOU and messing with interface costs!
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Rack1SW4#sh ip route 150.1.9.0
Routing entry for 150.1.9.0/24
Known
via "ospf 1", distance 110, metric 25491,
type inter
area #total metric = 25491; INTER AREA
Last update from 155.1.108.8 on Ethernet3/0, 00:02:47 ago
Routing Descriptor Blocks:
* 155.1.108.8, from 150.1.5.5, 00:02:47 ago, via Ethernet3/0 #150.1.5.5 = ABR as its INTER AREA
Route metric is 25491, traffic share count is 1
Rack1SW4#sh ip ospf data sum 150.1.9.0
OSPF Router with ID (223.255.255.255) (Process ID 1)
Summary Net Link States (Area 3)
Routing Bit Set on this LSA in topology Base with MTID 0
LS age: 2 (DoNotAge)
Options: (No TOS-capability, DC, Upward)
LS Type: Summary Links(Network)
Link State ID: 150.1.9.0 (summary Network Number)
Advertising Router: 150.1.5.5 #confirmation that this is the ABR being used
LS Seq Number: 80000001
Checksum: 0x5B8A
Length: 28
Network Mask: /24
MTID: 0 Metric: 22461 #this is the metric from the perspective of 150.1.5.5 (ABR)
Rack1SW4#sh ip ospf border-routers | i 150.1.5.5
i 150.1.5.5 [3030] via 155.1.108.8, Ethernet3/0, ABR, Area 3, SPF 5 #cost to ABR
So, the cost from SW4 to 150.1.9.0 is 25491;
This is made up of: SW4 to ABR = 3030 *PLUS* ABR to 150.1.9.0 = 22461
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Am I being too simplistic? Adding the cost of the ABR using "sh ip ospf border-routers" to the metric that the ABR sees to the destination?
Thanks.