In this configuration The internal network is managed by OSPF and every address is correctly redistribuited.
There are 3 EBGP routers connected to 3 uplinks (2 of them are IX) which receive Full routing tables from EBGP peerings (over 1.7k routes in one of them).
Those routers are connected each other with IBGP peering and they exchange nicely the routes (some filtering fix the target scopes and some other stuffs).

R2 receives IBGP routes of R4,R5,R6 from both R1 and R3 and MED attribute balances shortest path to the OSPF routers (Awesome! )

The issue is:

R2 receives 1.1.1.1 (assigned on a interface of R1) via R3 which receives it via OSPF. On /routing bgp advertisement i cannot see the route 1.1.1.1/32 on IBGP peer advertisement. On /ip route i see the route 1.1.1.1 to IBGP R3.
I enabled redistribuite connected on R1 but it still doesn't announce any connected route (DAC) to R2.
Any advice?

Post "/routing export" and "/interfaces" of your 3 BGP routers.
Without it, I think it will be difficult to help you.

A couple of quick pointers:-
iBGP requires every participating router to talk to each other, i.e. a mesh..... so you also need to rung iBGP between R1 & R3

Additionally, I would include R2 into the OSFP network as well.
so your connected interfaces route via ospf....(since ospf is going to be preferred over iBGP)

@faisali
This might be a good hint to make it work, but looks more like a workaround than a correct solution. It is true that ospf routes will be prefered, but there are no BGP routes announced, that's why OSPF is prefered.

@faisali
This might be a good hint to make it work, but looks more like a workaround than a correct solution. It is true that ospf routes will be prefered, but there are no BGP routes announced, that's why OSPF is prefered.

Please see this..
http://wiki.mikrotik.com/index.php?titl ... edirect=no

You may also have a 'filter issue'.... best way to troubleshoot is, to see what you are advertising, and on the other router what you are receiving.

eBGP Routes are preferred over OSPF, but in case of iBGP, OSPF routes have smaller distance.

Thanks faisali,
my problem was that IBGP wasn't announcing any route, and R2 doesn't have OSPF daemons running.
All of sudden, routes on IBGP started incoming, i don't really know why though... I just added one of the connected routes to BGP networks announce. After that, even the other connected routes were announced to R2. Now i have disabled the BGP network announced and it still works. A fine tuning to the filter i got the right weights and it works as intended.
Dunno the reasons of this behaviour.