OSPF - Can't get Symmetrical routing working

RouterOS Forwarding Protocols
1

Hi!

So I have another weird network issue that I seem to be unable to solve. After days of attempting.

The scenario is as follows. I have a full OSPF ring on a /29 Subnet, Broadcast mode. The OSPF ring has 3 nodes on a VLAN.

Two of the nodes are Mikrotik based and one is a Cisco, also in broadcast mode. Now the problem.

Node 1 needs to flow to Node 3 Directly. This is because there is a VPLS involved. And this is working. HOWEVER, the data coming back from Node 3 is going to Node 2. Which is supposed to be a backup link. I’ve set the cost of Node 2 (Node 2 is a Cisco) to 999, changed the priority, however, seem to be completely unable to Get node 3 to send data back directly to Node1. I’ve played with everything possible and wanted to check if there was anything else I can do, other than cost and priority. Node 2 is a core router that has a limit on the link going out to node 3 which is not ideal at all and causes huge latency when flowing this route.

Currently, Costs are set to 10 on Node 1, 300 on Node 3 and 999 on Node 2. Priority all 1.

is there something i am missing?

2

A few things to look at

  1. Cost can be set on both sides of the link, so make sure you’ve set the cost on the correct side
  2. Cost does not cross areas, if one of the links is in a different area, that could also contribute to the problem

Can you post the MikroTik and Cisco configs?

3

Config attached:

Node 1 - RB3011

/ip address
add address=x.x.x.2/29 interface=vlan3246-Layer3 network=x.x.x.x
/routing ospf instance
set [ find default=yes ] redistribute-connected=as-type-1 redistribute-static=
as-type-1 router-id=10.0.0.20
/routing ospf interface
add cost=15 interface=vlan3246-Layer3 network-type=broadcast
add interface=vlan124-L3via6509 network-type=broadcast
/routing ospf network
add area=backbone network=x.x.x.x/29
add area=backbone network=x.x.x.x/30

Node 2 (Cisco 4900M)

interface Vlan3246
ip address x.x.x.2 255.255.255.248
ip ospf cost 999
counter ipv4 ipv6 separate

router ospf 1
log-adjacency-changes
redistribute connected metric-type 1 subnets

Node 3 - RB2011

/routing ospf instance
set [ find default=yes ] redistribute-connected=as-type-1 redistribute-static=
as-type-1 router-id=0.0.0.0
/ip address
add address=x.x.x.3/29 interface=vlan3246-Layer3 network=x.x.x.x
/routing ospf interface
add cost=300 interface=vlan3246-CityL3 network-type=broadcast
/routing ospf network
add area=backbone network=x.x.x.3/29

4

Can you also post the routing tables for each node and the IPs of the VPLS endpoints?