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