​​Summary:

Adjust the metric of OSPF to function well with speeds UP to 10G links

 

 

OSPF metric:

- how a router chooses the best route to a network


- ospf use metric as cost; rip uses metric as hop count

 

- cost = 100/bandwidth (mbps); that being said, out of box, ospf can not tell the difference between 100M, 1G, 10G network (if you do the math)

- to change an interface bandwidth

      int fa0/0

      bandwidth 100000

 

- you can change ospf manually, but not recommended

       ip ospf cost
 

 

Belt, Tie, Sock, Shoe:

router ospf 1
  auto-cost reference-bandwidth 10000

 

Sock#sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

     10.0.0.0/24 is subnetted, 3 subnets
O       10.1.3.0 [110/74] via 10.1.2.2, 01:24:21, Serial1/0  !---------------------------------------------it costs me 74 to reach out to 10.1.3.0 network
C       10.1.2.0 is directly connected, Serial1/0
C       10.1.1.0 is directly connected, FastEthernet0/0


Sock#sh int s1/0
Serial1/0 is up, line protocol is up
  Hardware is M4T
  Internet address is 10.1.2.1/24
  MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,  !------------------------------------------------------ here the S1/0 bandwidth is 1.544mbps
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation HDLC, crc 16, loopback not set
  Keepalive set (10 sec)
  Restart-Delay is 0 secs
  Last input 00:00:00, output 00:00:02, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: weighted fair
  Output queue: 0/1000/64/0 (size/max total/threshold/drops)
     Conversations  0/1/256 (active/max active/max total)
     Reserved Conversations 0/0 (allocated/max allocated)
     Available Bandwidth 1158 kilobits/sec
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     6203 packets input, 458630 bytes, 0 no buffer
     Received 3385 broadcasts, 0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
     6192 packets output, 458835 bytes, 0 underruns
     0 output errors, 0 collisions, 3 interface resets
     0 output buffer failures, 0 output buffers swapped out
     4 carrier transitions     DCD=up  DSR=up  DTR=up  RTS=up  CTS=up