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mcrose
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OSPF Type 5 LSA flooding but not added to route table?

Tue Aug 23, 2011 5:46 pm

I'm seeing an issue with a OSPF External type 1 redistributed static route not being installed in the network's routing tables since upgrading some point to point backhauls to Ubnt hardware. I'm in the process of migrating the network's point to point links to use NBMA OSPF as with broadcast traffic the OSPF links were dropping periodically (once or twice a day) and causing the static route to not get routed. The OSPF session would die due to a lost packet or similar link level behavior and reinitialize within a few seconds.

When the issue occurs, this particular redistributed static route is the only route that doesn't come up. The native OSPF networks and the other redistributed connected/static (about a half dozen from this router) do come up properly. The only difference between this route and the others is that it's announced elsewhere on the network as well.

When OSPF drops and renegotiates the Mik1-Mik2 connection, all devices on the network list the affected redistributed network (10.0.0.0/26) as an external LSA with the correct originator (Mik1 in the diagram - 192.168.100.1). However, the network does not show up in any devices' routing table.

The issue can be fixed by disabling and reenabling the affected static routes in the originating Mik1 router. This triggers a reannouncement and reflooding and once done the network has a route to the network again.

I've got a simplified network map below:
Mik1 - OSPF area 1
-----------------------------------------------------
| ether1 - 192.168.100.1                            |
| 192.168.100.0/24 - Network                        |
| 10.0.0.0/26 via 192.168.100.1 - External type 1   |
|                                                   |
| ether2 - 172.16.0.1                               |
| 172.16.0.0/29 - Network                           |
-----------------------------------------------------

                          | Mik1-ether2 <-> Mik2-ether2
Mik2 - OSPF area 1                          
-----------------------------------------------------
| ether1 - 192.168.101.1                            |
| 192.168.101.0/24 - Network                        |
|                                                   |
| ether2 - 172.16.0.2                               |
| 172.16.0.0/29 - Network                           |
|                                                   |
| ether3 - 172.16.0.9                               |
| 172.16.0.8/29 - Network                           |
-----------------------------------------------------

                          | Mik2-ether3 <-> Mik3-ether2 - this is the link that was updated
Mik3 - OSPF area 1                          
-----------------------------------------------------
| ether1 - 192.168.102.1                            |
| 192.168.102.0/24 - Network                        |
|                                                   |
| ether2 - 172.16.0.10                              |
| 172.16.0.8/29 - Network                           |
-----------------------------------------------------
 
                          | Mik3-ether1 <-> Cisco1-FE0/0
Cisco1 - ABR - FE0/0 area 1, FE0/1 area 0                          
-----------------------------------------------------
| FE0/0 - 192.168.102.2                             |
| 192.168.102.0/24 - Network                        |
|                                                   |
| FE0/1 - 172.16.0.17                               |
| 172.16.0.16/29 - Network                          |
-----------------------------------------------------
 
                          | Cisco1-FE0/1 <-> Cisco2-FE0/0
Cisco2 - OSPF area 0                        
-----------------------------------------------------
| FE0/0 - 172.16.0.18                               |
| 172.16.0.16/29 - Network                          |
|                                                   |
| Serial0/0 - 172.16.0.25                           |
| 172.16.0.24/29 - Network                          |
| 10.0.0.0/26 via 172.16.0.26 - External type 2     |
-----------------------------------------------------
The intended behavior is to route 10.0.0.0/26 over one of two routes out of the network, preferring the route from Mik1 if available. The Type-1 external LSA announced by that router should have priority over the Type-2 external LSA announced by Cisco2 in all situations and as long as Mik1 sees 192.168.100.1 up it will announce the route. Cisco2 fails over and announces the route through itself in case of an outage at 192.168.100.1 or if there're broken links between it and Mik1.

I've tried dumping the debug for ospf while this happens to a text file so I can audit what's going on but it's not complete -- keeps getting filled with x messages dropped lines. It appears, however, that the routes are being flooded from both Mik1 and Cisco2 simultaneously and the result is that nothing gets routed. I see the networks from Mik1 get installed to the main routing table, then an announcement from cisco2 is seen, the network gets retransmitted with that as the originator, then that LSA is deleted.

However, I'm not convinced that going unicast OSPF will resolve the issue; as I did see it crop up while the links were cycling while implementing NBMA. It may help with the random losses as I expect the OSPF session to drop less now, but it's potentially not the root cause. Has anyone seen behavior like this before? Do Mikrotiks have any diagnostic tools available to show why a network is not being routed even though it's showing up as a LSA?
 
fewi
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Re: OSPF Type 5 LSA flooding but not added to route table?

Fri Aug 26, 2011 7:29 pm

I would send an email to support@mikrotik.com. If an LSA is present but not installed, but then installed when a static route is disabled and re-enabled - that sounds like a bug in the OSPF implementation.
Specific answers require specific questions. When in doubt, post the output of "/ip address print detail", "/ip route print detail", "/interface print detail", "/ip firewall export", and an accurate network diagram.
 
Ascii
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Re: OSPF Type 5 LSA flooding but not added to route table?

Wed Nov 02, 2011 8:19 pm

I have exact the same problem, any word from mikrotik about this problem
 
blake
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Re: OSPF Type 5 LSA flooding but not added to route table?

Mon Nov 07, 2011 11:49 pm

When the issue occurs, this particular redistributed static route is the only route that doesn't come up. The native OSPF networks and the other redistributed connected/static (about a half dozen from this router) do come up properly. The only difference between this route and the others is that it's announced elsewhere on the network as well.
Thanks for that info. I'm experiencing the same problem with a default route that I advertise from two locations in my network. I was initially just following this thread (http://forum.mikrotik.com/viewtopic.php?f=14&t=54076), but I will now keep an eye on this one to see if anyone else comes up with a solution to this.
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iDen
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Re: OSPF Type 5 LSA flooding but not added to route table?

Wed Nov 16, 2011 11:09 am

think i have same problem
my original thread: http://forum.mikrotik.com/viewtopic.php?f=14&t=56735
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changeip
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Re: OSPF Type 5 LSA flooding but not added to route table?

Wed Nov 16, 2011 6:44 pm

I think I have seen this behavior as well. It's intermittent, and the fact you probably have ospf flapping more than normal you see the problem occur more. With nbma neighbors I never see this happen (across ubnt or mt). But, when I work on the core where the default route is being advertised sometimes our default gateway will not come back up - either I quickly reboot the core router or manually enable / disable it's static route temporarily.

Let's figure this out. My gut feeling is this has something to do with Type 2 routes and when Type 1 goes away it doesn't always come back into the routing table. I never saw this problem until we started introducing Type 2 default routes for disaster recovery.
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Ascii
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Re: OSPF Type 5 LSA flooding but not added to route table?

Thu Nov 17, 2011 6:40 am

Last week I send a similar report to mikrotik and get this response:

> Configure NBMA on wireless links and see if it helps.
> Instructions are in the link below:
> http://wiki.mikrotik.com/wiki/Manual:OS ... A_networks


I have over 20 sites running OSPF (3-5 routers per site, 3 areas). I can´t change all my routers to NBMA.
Change all backhaul from station to station-wds and the problem persist.


I have same problem again today, look like external type-5 LSA sometime don´t get installed when it is flooded from multiple locations.
somethings that my configuration have in common with the others in this thread:
- multiple ospf areas.
- external route flooded from two locations in the network.

All my external routes are type 1 (don´t have type 2 in my entire network)


pd: sorry for my english
 
changeip
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Re: OSPF Type 5 LSA flooding but not added to route table?

Thu Nov 17, 2011 6:51 pm

We use ONLY nbma on wireless links, and broadcast mode is only used on ethernet segments within a physical switch. This has nothing to do with the mode, it only has to do with routes in the LSA that are not getting installed in the routing table. Using the wrong mode just makes the problem more common because the routes are flapping more. I will try to get some logging going and maybe a script to capture it next time this happens. Its a disaster when it does happen because the default gateway disappears and all customers are wondering why internet is down, so I don't want to try to make it happen to troubleshoot it : )
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Ascii
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Re: OSPF Type 5 LSA flooding but not added to route table?

Tue Nov 22, 2011 7:51 pm

I make sure that all my externals are flooded only from one place in the network.

For example an /28 flooded from 2 locations (main link, backup link). Change to 2x /29 (main link) and /28 backup link.

I don´t have a problem since a make this changes a week ago.
 
changeip
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Re: OSPF Type 5 LSA flooding but not added to route table?

Wed Nov 23, 2011 12:03 am

how can you do that with 0.0.0.0/0 routes ?
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Ascii
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Re: OSPF Type 5 LSA flooding but not added to route table?

Wed Nov 23, 2011 8:39 am

I have 2 border routers (same location, 2 providers) than flood 0.0.0.0/0 into the ospf cloud
However one of the border routes have Default Route metric set to 2 ,
this way I only have one 0.0.0.0/0 with metric 1 from the other border route.

something like
/routing ospf instance set metric-default=2 default


if you want you can set a backup default in case that ospf default don´t get installed
/ip route add dst-address=0.0.0.0/0 gateway=a.b.c.d distance=130
 
mcrose
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Re: OSPF Type 5 LSA flooding but not added to route table?

Thu Dec 15, 2011 7:47 pm

We use ONLY nbma on wireless links, and broadcast mode is only used on ethernet segments within a physical switch. This has nothing to do with the mode, it only has to do with routes in the LSA that are not getting installed in the routing table. Using the wrong mode just makes the problem more common because the routes are flapping more. I will try to get some logging going and maybe a script to capture it next time this happens. Its a disaster when it does happen because the default gateway disappears and all customers are wondering why internet is down, so I don't want to try to make it happen to troubleshoot it : )
I'm glad to see this topic getting some movement. You're probably right about the E2/E1 typeroutes. Since migrating the wireless links over to NBMA it doesn't crop up as often, as the ospf link isn't flapping all the time. However, I still see it intermittently when the location loses its OSPF link for another reason -- link outage, etc. However, simply moving to NBMA masks the problem, it does not eliminate it.
 
Ascii
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Re: OSPF Type 5 LSA flooding but not added to route table?

Fri Dec 16, 2011 12:03 am

I sent two Supout.rif (taken at the time of the problem), and get some generic response about NBMA .

Ticket#2011110166000502
Date 1/Nov/2011

For mitigation look at my two previous post in this thread, I don´t have a single problem after the changes.
 
changeip
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Re: OSPF Type 5 LSA flooding but not added to route table?

Fri Mar 09, 2012 9:27 am

I make sure that all my externals are flooded only from one place in the network.

For example an /28 flooded from 2 locations (main link, backup link). Change to 2x /29 (main link) and /28 backup link.

I don´t have a problem since a make this changes a week ago.
Are you saying that instead of having a /28 with a handful of routers participating in broadcast ospf, to actually use a /30 between each router so that ospf peers aren't all on the same subnet? Im starting to think that might be part of this problem ... Ive seen effects of that in another situation, just never though it might be part of the problem with default routes not getting installed properly.
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Ascii
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Re: OSPF Type 5 LSA flooding but not added to route table?

Fri Mar 09, 2012 6:34 pm

NO, you can keep you peers in the same subnet.
Type 5 LSA are used for external routes, not peers.

make sure that you don´t redistribute connected routes.
make sure that all yours externals (Static routes) are flooded only from one place in the network.

A

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