Tuesday, August 2, 2011

Configuring basic OSPF


Brief tutorial on how to configure a single area OSPF with no authentication. 
Overview: 4 routers configured with 4 loopbacks. 




Relevant configurations for R1, R2, R3, R4 are posted below.




R1
interface FastEthernet1/0
 ip address 10.0.0.1 255.255.255.0
 duplex auto
 speed auto
end
interface Loopback0
 ip address 172.16.1.1 255.255.255.0
end
router ospf 1
 log-adjacency-changes
 redistribute connected subnets 
 network 10.0.0.0 0.0.0.255 area 0

R2
interface FastEthernet1/0
 ip address 10.0.0.2 255.255.255.0
 duplex auto
 speed auto
end
interface Loopback0
 ip address 172.16.2.1 255.255.255.0
end
router ospf 1
 log-adjacency-changes
 redistribute connected subnets
 network 10.0.0.0 0.0.0.255 area 0


R3
interface FastEthernet1/0
 ip address 10.0.0.3 255.255.255.0
 duplex auto
 speed auto
end
interface Loopback0
 ip address 172.16.3.1 255.255.255.0
end
router ospf 1
 log-adjacency-changes
 redistribute connected subnets
 network 10.0.0.0 0.0.0.255 area 0


R4
interface FastEthernet1/0
 ip address 10.0.0.4 255.255.255.0
 duplex auto
 speed auto
end
interface Loopback0
 ip address 172.16.4.1 255.255.255.0
end
router ospf 1
 log-adjacency-changes
 redistribute connected subnets
 network 10.0.0.0 0.0.0.255 area 0


R1#sh ip ospf neighbor
Neighbor ID     Pri   State           Dead Time   Address         Interface

10.0.0.2          1   FULL/DROTHER    00:00:30    10.0.0.2        FastEthernet1/0
10.0.0.4          1   FULL/BDR        00:00:34    10.0.0.4        FastEthernet1/0
172.16.3.1        1   FULL/DROTHER    00:00:34    10.0.0.3        FastEthernet1/0


R1#sh ip ospf database
            OSPF Router with ID (10.0.0.1) (Process ID 1)

                Router Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum Link count

10.0.0.1        10.0.0.1        596         0x80000003 0x00CD35 1
10.0.0.2        10.0.0.2        542         0x80000002 0x00CD33 1
10.0.0.4        10.0.0.4        595         0x80000002 0x00C931 1
172.16.3.1      172.16.3.1      479         0x80000003 0x00781D 1
                Net Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum

10.0.0.1        10.0.0.1        482         0x80000003 0x00DF54
                Type-5 AS External Link States

Link ID         ADV Router      Age         Seq#       Checksum Tag

172.16.1.0      10.0.0.1        440         0x80000001 0x00F6E0 0
172.16.2.0      10.0.0.2        528         0x80000001 0x00E5EF 0
172.16.3.0      172.16.3.1      480         0x80000001 0x00938C 0
172.16.4.0      10.0.0.4        581         0x80000001 0x00C30E 0

R1# sh ip ospf interface
FastEthernet1/0 is up, line protocol is up
  Internet Address 10.0.0.1/24, Area 0
  Process ID 1, Router ID 10.0.0.1, Network Type BROADCAST, Cost: 1
  Transmit Delay is 1 sec, State DR, Priority 1
  Designated Router (ID) 10.0.0.1, Interface address 10.0.0.1
  Backup Designated router (ID) 10.0.0.4, Interface address 10.0.0.4
  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 4 msec
  Neighbor Count is 3, Adjacent neighbor count is 3
    Adjacent with neighbor 10.0.0.2
    Adjacent with neighbor 10.0.0.4  (Backup Designated Router)
    Adjacent with neighbor 172.16.3.1
  Suppress hello for 0 neighbor(s)

R1#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
     172.16.0.0/24 is subnetted, 4 subnets
O E2    172.16.4.0 [110/20] via 10.0.0.4, 00:11:30, FastEthernet1/0
C       172.16.1.0 is directly connected, Loopback0
O E2    172.16.2.0 [110/20] via 10.0.0.2, 00:10:37, FastEthernet1/0
O E2    172.16.3.0 [110/20] via 10.0.0.3, 00:09:39, FastEthernet1/0
     10.0.0.0/24 is subnetted, 1 subnets
C       10.0.0.0 is directly connected, FastEthernet1/0
R1#ping 172.16.4.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.4.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/20/40 ms

More articles to come so stay tuned!!