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Open Shortest Path First (OSPF)

OSPF is a link-state dynamic routing protocol that discovers neighbors, exchanges link information, and computes the shortest path using Dijkstra’s algorithm. Each router uses a unique Router-ID and participates in one or more OSPF Areas.

Topology OSPF on MikroTik​

Addressing Plan​

RouterInterfaceIPLayer
MT12ether1172.16.19.2/24Link to Upstream
MT12vlan10172.16.20.1/24Link to MT11
MT11vlan10172.16.20.2/24Link to MT12

We will create a custom area name instead of the default backbone.

Create OSPF Instance on MT12​

an instance defines router-id and global settings.

Input:

/routing ospf instance add name=office-inst router-id=172.16.20.1

Create OSPF Area on MT12​

an area groups routers to exchange LSAs.

Input:

/routing ospf area add name=office-area area-id=0.0.0.0 instance=office-inst

Enable OSPF on VLAN Interface MT12​

OSPF only forms neighbors on enabled interfaces.

Input:

/routing ospf interface add network-type=broadcast interface=vlan10

instruct OSPF to announce a subnet.

Input:

/routing ospf network add area=office-area network=172.16.20.0/24
/routing ospf network add area=office-area network=172.16.19.0/24

Create OSPF instance on MT11​

router-id must be unique.

Input:

/routing ospf instance add name=office-inst router-id=172.16.20.2

Create OSPF Area on MT11​

area must match to become neighbors.

Input:

/routing ospf area add name=office-area area-id=0.0.0.0 instance=office-inst

Enable OSPF on VLAN Interface MT11​

OSPF will send Hello packets on this link.

Input:

/routing ospf interface add network-type=broadcast interface=vlan10

both sides advertise the shared LAN.

Input:

/routing ospf network add area=office-area network=172.16.20.0/24

Verify OSPF Neighbors​

Full state means LSDB synchronized.

Input:

/routing ospf neighbor print

Output:

INSTANCE         STATE        NEIGHBOR-ID     ADDRESS         INTERFACE
office-inst      Full         172.16.20.1     172.16.20.1     vlan10

The output shows adjacency formed.

Show Learned OSPF Routes​

OSPF routes appear with “o” flag.

Input on MK11:

/ip route print where ospf

Output:

Flags: X - disabled, A - active, D - dynamic, C - connect, S - static, r - rip, b - bgp, o - ospf, m - mme, 
B - blackhole, U - unreachable, P - prohibit 
 #      DST-ADDRESS        PREF-SRC        GATEWAY            DISTANCE
 0 ADo  172.16.19.0/24                     172.16.20.1             110

The output shows dynamically learned routes.