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spanz
New Contributor III

BGP Advertising issue with single prefix

Hello,

I have to set BGP on my Fortigate 600E appliance with my isp.

I already configured neighbors, AS and advertised routes and everything is working fine except:

There's 1 network in my routing table which is 10.10.0.0/16

I have to advertise to my neighbor only the 10.10.60.0/24 network and not the whole /16 subnet (he set it in his prefix filter) so

I added another static route of 10.10.60.0/24 for my local routing table with the same gateway as the 10.10.0.0/16 has, and advertised it to my BGP Neighbor.

 

Now, my neighbor gets all the networks I advertise except the 10.10.60.0/24

 

Routing table (only the routes assosiated with that issue) : 

S 10.10.0.0/16 [1/0] via 15.15.15.1, port5, [0/50] S 10.10.60.0/24 [10/0] via 15.15.15.1, port5

 

BGP Advertise to neighbor (get router info bgp neighbors <ip address of neighbor> advertised-routes):

*> 10.10.60.0/24   93.52.12.2                  100  32768        0 i <-/->

 

 

I dont see what is the problem.. I can see I have it in my local routing table and advertise the network but they still cant get it.

 

Appreciate any help! 

Thanks

5 REPLIES 5
Toshi_Esumi
SuperUser
SuperUser

Is this MPLS circuit or Internet with the ISP? If MPLS, likely it's summarized by the provider because the /24 route is redundant. Either ask the provider or try filtering out the /16 route from advertisement.

spanz
New Contributor III

Thanks for the reply. These are all private addresses, and not internet.. it is indeed MPLS or IPVPN ... However.. And the /16 is not advertised. It is just in the routing table in my fortigate, For BGP im advertising only the /24 and the isp put the /24 in his prefix filter list as all the other network Im advertising to him (they are all /24 and all work except this one.)
Toshi_Esumi

Then you already know nothing you can do on your FGT. Call the provider/MSP (managed service provider) to ask why they're dropping it.

spanz
New Contributor III

I posted this issue after I tried to reconfigured it all, so as my ISP.

I think the problem is on my side since all my /24 advertisements works fine and have a corresponding route in the routing table, and this specific one is originally /16 in my routing table, and I just made another /24 route for the BGP route to be advertised.

 

maybe I should change costs at the FGT routing table ??

spanz
New Contributor III

Solved.

The problem was on the ISP side..

Wrong settings of the receiving prefix filter list.

Thank for your help !!

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