OSPF on 3560 has a high metric in my simple lab

[stephan-helmut]

I built a simple ospf lab with 2 3560's (really extreme simple) and single area design with area 0.

the show ip route issued on my core prints some weird metrics that I don't understand yet:

     1.0.0.0/32 is subnetted, 1 subnets
C       1.1.1.1 is directly connected, Loopback1
     2.0.0.0/32 is subnetted, 1 subnets
O       2.2.2.2 [110/1001] via 10.254.0.2, 01:09:06, GigabitEthernet0/2
     10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
O       10.0.10.0/24 [110/2000] via 10.254.0.2, 01:09:06, GigabitEthernet0/2
O       10.0.1.0/24 [110/2000] via 10.254.0.2, 01:09:06, GigabitEthernet0/2
O       10.0.20.0/24 [110/2000] via 10.254.0.2, 01:09:06, GigabitEthernet0/2
C       10.254.0.0/30 is directly connected, GigabitEthernet0/2

It's a 3 tier campus design where the access layer is l2 based. Connection between core and distribution is 1 gig cable and distribution to access are 4 fa cables via etherchannel.

However, I issued the ospf auto-cost bandwith 1000000 command but still...why do I get those metrics with that high value ???

[Asemmoqbel]

Hi,

Can you post the output for the below command

show ip ospf interface GigabitEthernet0/2

and also the above command for the interface connected to GigabitEthernet0/2 on the other side.

[stephan-helmut]

upper device:

GigabitEthernet0/2 is up, line protocol is up (connected) 
  Internet Address 10.254.0.1/30, Area 0 
  Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 1000
  Enabled by interface config, including secondary ip addresses
  Transmit Delay is 1 sec, State BDR, Priority 1
  Designated Router (ID) 2.2.2.2, Interface address 10.254.0.2
  Backup Designated router (ID) 1.1.1.1, Interface address 10.254.0.1
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    oob-resync timeout 40
    Hello due in 00:00:01
  Supports Link-local Signaling (LLS)
  Cisco NSF helper support enabled
  IETF NSF helper support enabled
  Index 1/1, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 1, maximum is 1
  Last flood scan time is 0 msec, maximum is 0 msec
  Neighbor Count is 1, Adjacent neighbor count is 1 
    Adjacent with neighbor 2.2.2.2  (Designated Router)
  Suppress hello for 0 neighbor(s)
  Message digest authentication enabled
    Youngest key id is 1

below device:

GigabitEthernet0/2 is up, line protocol is up (connected) 
  Internet Address 10.254.0.2/30, Area 0 
  Process ID 1, Router ID 2.2.2.2, Network Type BROADCAST, Cost: 1000
  Transmit Delay is 1 sec, State DR, Priority 1
  Designated Router (ID) 2.2.2.2, Interface address 10.254.0.2
  Backup Designated router (ID) 1.1.1.1, Interface address 10.254.0.1
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    oob-resync timeout 40
    Hello due in 00:00:01
  Supports Link-local Signaling (LLS)
  Cisco NSF helper support enabled
  IETF NSF helper support enabled
  Index 5/5, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 1, maximum is 2
  Last flood scan time is 0 msec, maximum is 0 msec
  Neighbor Count is 1, Adjacent neighbor count is 1 
    Adjacent with neighbor 1.1.1.1  (Backup Designated Router)
  Suppress hello for 0 neighbor(s)
  Message digest authentication enabled
    Youngest key id is 1

[Asemmoqbel]

The ospf protocol uses bandwidth for calculating metric. when you issued auto-cost bandwidth 1000000 on your routers, the connected interfaces cost will be 1000 as the following formula Auto-cost / interface BW = (1000000 / 1000 = 1000)

So I assume these networks 10.0.10.0/24, 10.0.20.0/24, 10.0.1.0/24 are configured on another router attached to the below device which means these networks will pass two links with cost of 1000 and finally to calculate the metric to the final destination you sum the cost of all the links that the packet have traveled through. the metric cost in our scenario will be shown on the upper device as 2000 (1000 +1000).


I hope this helps..

[paul driver]

Hello

This is due to your auto-cost reference bandwidth it has increase 1gb port from cost of 1 to a cost of a 1000

default cost

100mb - cost 1
1000mb -cost 1

auto-cost reference bandwidth 1000

100mb - cost 10
1000mb -cost 1

auto-cost reference bandwidth 10000

100mb - cost 100
1000mb -cost 10

auto-cost reference bandwidth 100000

100mb - cost 1000
1000mb -cost 100

auto-cost reference bandwidth 1000000

100mb - cost 10000
1000mb -cost 1000

res
Paul