OSPF-out filter not working

RouterOS General
1

I know it is routing-test, but has anyone made the ospf-out filter work?

I have read about 6 different threads in the forums, and they all go
silent after this determination.

Has anyone tested ospf filters in 3.0bx? Do they work there?

Thanks,
Richard

2

are you sure that route is not filtered?

please post your route filter here, and describe what you wanted to do with that filter

3

Here is what I’m seeing, and tell me if it is what the filter is supposed to be doing…

When I put in the filters, they seem to apply to what routes that particular router generates only.

Example, I have a MT as a ABR between to areas, I only want to propagate some routes between the borders.

If I put in filters , they do filter what that specific router generates ( statics / connected ), but not what it hears inter-area and propagates to the other area.

Sorry, I’m used to cisco filters, and I’m assuming the MT filters should work like those..

Richard

4

Correct, and that’s exactly how it should be.

This can not be done with OSPF filters. An OSPF router must never drop LSAs - doing so would potentially mess up the link state/topology calculation of other OSPF routers. It is allowed to be selective about which LSAs it installs into its own routing table (that would be the job of OSPF import filtering) or what external (i.e. non-OSPF-originated) routing information (such as static or connected routes) it considers to generate LSAs for in the first place (that - and only that - is the job of OSPF output filters).

Cisco does not filter received LSAs either, they also must (and do) propagate them.

–Tom

5

I would swear this is what we are doing with this..

http://www.cisco.com/en/US/products/sw/iosswrel/ps1839/products_feature_guide09186a00800b5d4f.html

Feature Overview

The OSPF ABR Type 3 LSA Filtering feature extends the ability of an ABR that is running the OSPF protocol to filter type 3 link-state advertisements (LSAs) that are sent between different OSPF areas. This feature allows only packets with specified prefixes to be sent from one area to another area and restricts all packets with other prefixes. This type of area filtering can be applied out of a specific OSPF area, into a specific OSPF area, or into and out of the same OSPF areas at the same time. This feature is supported by the addition of the area filter-list command in router configuration mode.

I’ll have to check out Cisco configs.. maybe they are all generated by the routers, but I’m pretty sure not.

Richard

6

Richard,

OK, I kind of missed that you were specifically talking about inter-area filtering (though you clearly said so, I should have read your post more carfully).

What I wrote about routers not being allowed to suppress LSAs is true within one area, inter-area is a different thing and of course routing information might be suppressed, summarized, modified etc. between areas.

From your observation it appears that the OSPF-in/out filtering in RouterOS only applies to the scenario that I described and does not apply to the inter-area scenario that you’re trying to configure, but I’m guessing here as I never tried inter-area filtering with RouterOS. Maybe one of the MT guys can shed some light on the capabilities of the RouterOS OSPF implementation regarding this particular feature…

–Tom

7

Ping..

Anything from Mikrotik on this?
3.0x maybe?

Thanks,
Richard

8

only external routes can be filtered

list of routes that can be filtered is here:
/routing ospf status lsa print external

9

Hrm..

[admin@xxxxxx] routing ospf> /routing ospf status lsa print external
no such command or directory (status)

V2.9.40 on a 532 routing-test enabled

I do want to filter external routes… in-between areas.

Richard

10

I believe that command is for v3beta and not supported on RouterOS 2.9

Yeah, the routing information initially came from an external source, but the place where you’d like the filter to apply is when the routing information is propagated from one OSPF area to another, but as it appears RouterOS does not allow a filter to be used for that operation. It can only filter the external routing information at the very first router where it is imported from external into OSPF. Once it is inside OSPF and goes from area to area there’s no more filtering…

–Tom

11

Yes it’s for v3, sorry

12

Now that the MT guys are back from MUM, can I get a ruling on this?

Richard

13

in v2.9.41 OSPF works very very good, try upgrading and then try again

14

ROS 2.9.x does not support inter-area filtering, and it looks like it is not planned in ROS 3.0 either. Just keep your OSPF clean and don’t redistribute stuff into OSPF that is not needed. This will keep things simple.