Table of Contents
I assume the following setup:
Router1 (Some external router) , with AS: 65532
Mikrotik router (our internal router) , with AS: 65535
Network prefix: 1.1.1.1/24 , delegated to AS 65535 (our internal router)
Router1.IP == 1.1.1.1/24
Mikrotik.IP == 1.1.1.2/24
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1. Enable BGP on the Mikrotik router
[admin@MikroTik] /interface> /routing bgp instance set default as=65535 redistribute-static=no router-id=1.1.1.2
2. Add our network to BGP on Mikrotik
[admin@MikroTik] > /routing bgp network add network=1.1.1.1/24 comment="Network delegated to our AS: 65535"
3. Create input/output filters on Mikrotik router
We must create input/output filters on our router in order we to NOT annouce other network.
When using invert-match=yes, we tell the router to discard everything BUT the prefix stated
# Allow only 1.1.1.1/24 as annoucements [admin@MikroTik] > /routing filter add chain=to_R1 prefix=1.1.1.1/24 invert-match=yes action=discard
4. Add BGP neighbour R1 to Mikrotik
[admin@MikroTik] > /routing bgp peer add remote-address=1.1.1.1 remote-as=65532
5. Finally … Validate the route for the network
[admin@MikroTik] /routing bgp advertisements> /ip route print where dst-address=1.1.1.1/24