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Unable to breakup IP range with /24 BGP to ISP

Posted: Wed Apr 10, 2024 5:40 pm
by Webnetism
Hi all

I have an issue with my newly setup Mikrotik CCR2116-12G-4S running 7.13.2

We are in the process of setting up an unmanaged internet connection
as part of that we advertise our two /24 ranges via BGP to our ISP
One range for customers and one range for company use.

We plan on breaking up the customer range into /28 /29 /30 depending on the customers needs.
Issue we are experiencing is if we set say a /29
then set a firewall with an address and GW in that /29
the Firewall eventually loses internet connection and never makes it out of our ISP's network.

I have spoken with our ISP and they say this is to be expected due to us having a private range and advertising the /24.
Is there a way i can set this up on our routers/FW and maintain internet connection

Re: Unable to breakup IP range with /24 BGP to ISP

Posted: Wed Apr 10, 2024 6:11 pm
by sirbryan
Without posting some of your config, it's hard to know how you're doing things.

But it sounds like what's happening is if you don't put the /24 somewhere on your router, it stops announcing it to your upstream provider. You need to at least blackhole route the /24 to the router itself so the BGP announcement(s) will work. Then you can break up the subnets across different interfaces and/or route them out to your downstream routers.

Re: Unable to breakup IP range with /24 BGP to ISP

Posted: Mon Apr 22, 2024 6:49 pm
by Webnetism
Hi Sirbryan

I understand this is quite a late response to what you said above.
Can you please elaborate more on what you were saying