← All lab tasks IP Connectivity Intermediate ~12 min · 3-device
Bring up OSPF on a 3-router triangle Three routers wired in a triangle (each router connects to both others). All interfaces are already IP'd and up. Configure single-area OSPF (area 0) on all three so every router sees the other two as Full neighbors and learns routes to the remote loopbacks. Then ping across.
R1 Lo0=1.1.1.1 Gi0/0 10.0.12.1/30 ─── 10.0.12.2/30 Gi0/0 R2 Lo0=2.2.2.2
Objectives ○ R1 ⇄ R2 Full adjacency ○ R1 ⇄ R3 Full adjacency ○ R2 ⇄ R3 Full adjacency ○ R1 has an OSPF route to 3.3.3.3/32 ✓ Done — OSPF converged across the triangle.
Try ping 3.3.3.3 from R1. show ip route shows O entries.
Hints Hint 1 — the pattern On each router: router ospf 1, then a network statement for each interface's subnet (including the loopback), all in area 0.
Hint 2 — wildcard mask Wildcards are the inverse of a netmask. For a /30 (mask 255.255.255.252), wildcard is 0.0.0.3. For a /32 loopback, wildcard is 0.0.0.0.
Hint 3 — full sequence # On R1
enable
conf t
router ospf 1
router-id 1.1.1.1
network 10.0.12.0 0.0.0.3 area 0
network 10.0.13.0 0.0.0.3 area 0
network 1.1.1.1 0.0.0.0 area 0
end
show ip ospf neighbor
# On R2
enable
conf t
router ospf 1
router-id 2.2.2.2
network 10.0.12.0 0.0.0.3 area 0
network 10.0.23.0 0.0.0.3 area 0
network 2.2.2.2 0.0.0.0 area 0
end
# On R3
enable
conf t
router ospf 1
router-id 3.3.3.3
network 10.0.13.0 0.0.0.3 area 0
network 10.0.23.0 0.0.0.3 area 0
network 3.3.3.3 0.0.0.0 area 0
endNeighbors reach Full the moment both sides have matching network area 0 statements — engine converges after every command.
