Thanks Tim. I think I understand why I misunderstood the examples now. They probably have the routers all L2 adjacent so they OSPF peer directly to each other, not through intermediate L3 devices. Then they don't need the IGP to have the full route table because they will look at the devices route table to make the next-hop decision. This makes the project far more complex than I was hoping for. I was hoping to avoid needing to stretch layer2 links between the devices. I'll have to re-assess my options. Thanks everyone who replied so quickly, I really appreciate it. -----Original Message----- From: Public <public-bounces@talk.mikrotik.com.au> On Behalf Of Tim Sandy Sent: Friday, 23 October 2020 10:30 AM To: MikroTik Australia Public List <public@talk.mikrotik.com.au> Subject: Re: [MT-AU Public] iBGP over OSPF Hey Philip, That's not really how recursive next hop works - That just means the router learning the route will still consider it valid if the next hop isn't directly attached. The intermediate L3 devices still need to have a route for the destination prefix. You can either: - Run iBGP on the intermediate switches - Connect the MT's together at layer 2 (either a normal vlan, EoIP, or something like GRE) - Run MPLS (on the intermediate switches too) - This will mean they look at the labels for forwarding (which will tell them to pass it on to the MT) rather than the L3 header. Hope that helps a bit. Cheers, Tim On Fri, 23 Oct 2020 at 10:21, Philip Loenneker < Philip.Loenneker@tasmanet.com.au> wrote:
Further clarification: I've set next-hop-self on the iBGP peers, and intend to have a full mesh between the routers. However I tested it before the full mesh was complete.
Here is a rough idea of what I've got:
MT Router -- (ospf) -- 2x L3 switches -- (ospf) -- MT router
MT routers advertise a loopback into OSPF and I am able to ping between MT routers. iBGP can establish and learn an abundance of routes - next-hop-self and update-source configured Route tables update and show the learned routes as valid with recursive next-hop of the loopback of the far-end MT router Traceroute to a subnet behind the far-end MT router stops at the first switch with "destination network unreachable" or equivalent because the switch itself has no route for the final destination
Are there any special settings required for the switches to process the recursive-next-hop address instead of the packets actual destination IP?
-----Original Message----- From: Public <public-bounces@talk.mikrotik.com.au> On Behalf Of Philip Loenneker Sent: Friday, 23 October 2020 10:01 AM To: public@talk.mikrotik.com.au Subject: [MT-AU Public] iBGP over OSPF
Hi all,
I have multiple MikroTik routers connected to non-MikroTik switches with OSPFv2 and v3 enabled on routers and switches (isolated VRF) to distribute loopbacks and interconnect subnets. No other subnets are in the IGP.
I can establish iBGP peers between loopbacks and exchange all routes (showing recursive next hop), including default route, but I can't connect to subnets behind other routers. In a traceroute the switches report that there is no valid next hop.
This all seems logical, except that all the guides say to do it this way.
I've seen some guides say to run MPLS over the top to get reachability, but I don't want to have that, especially since some routers are CHR and have issues with MPLS on some hypervisors.
Does anyone have any advice on this? Do I need to have L2 as adjacency between all routers eg with a tunnel over the OSPF loopbacks, or MPLS, or should this work as the guides all suggest? I'm sure I'm missing something obvious...
Regards, Philip _______________________________________________ Public mailing list Public@talk.mikrotik.com.au
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