12-28-2022 03:26 PM
I have 4 directly connected routers in square formation, 4 hosts, 1 attached to each router, each router has its own loopback 1.1.1.1 for R1 etc. each router has router ospf 1 and network 0.0.0.0 255.255.255.255 area 0 executed, I can ping every device with every other device (each router has 3 networks not including loopbacks, 2 networks for both connections to a router and 1 for the host). My problem is when I show ip ospf neighbors i dont see all of my routers in the list for each router. For example, R1 shows R2 and R3 as neighbors but not R4, R2 shows R1 and R4 but not R3. My pings do not consistently use the lowest ports from R4 to R1 given the cost is the same for every route.
Can someone please tell me what I am missing
12-28-2022 03:34 PM
this is not problem, you connect router in square design so each one see only two router, and the third missing.
what you need ?
you need SW in middle and connect all four router to this SW and you will see three router neighber in each router.
12-28-2022 04:05 PM - edited 12-28-2022 04:05 PM
Hello,
As @MHM Cisco World pointed out they have to be physically connected to each other, not just reachable across the network. Now what you will see is if you enter the command "show ip ospf database" they will show the same information (as long as they are in the same area) since all OSPF devices in the same area share a Link-State Database.
Secondly, OSPF uses cost and thats it for its metrics to calculate a path. It has nothing to do with lowest port number. If all costs are the same it will load balance (up to 4 by default). So the first ping will take one path and the second ping could take the other path. If you want consistency make one path with a lower cost and will always use that.
Hope that helps
-David
12-29-2022 08:33 AM
As @David Ruess correctly notes, pings will "round-robin" across OSPF ECMP.
12-28-2022 08:23 PM
Please provide an image of the topology. Also attach the zipped pkt file.
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