Mikrotik: BGP Dua Link No Transit

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Bgp-multihoming.png

Ada tiga (3) ISP

ISP1:

IP 192.168.1.1/24 menuju ISP3
IP 192.168.3.1/24 menuju ISP2
AS 10
IP 10.100.100.0/24
IP 10.100.200.0/24

ISP2

IP 192.168.2.1/24 - menuju ISP3
IP 192.168.3.2/24 - menuju ISP1
AS 20
IP 10.10.10.0/24
IP 10.10.20.0/24

ISP3 (kita)

IP 192.168.1.2/24 - menuju ISP1
IP 192.168.2.2/24 - menuju ISP2
AS 30
IP 10.1.1.0/24
IP 10.1.2.0/24 


Sambungan Fisik

ISP1


ISP1 ether0 -> ISP3 ether0
ISP1 ether1 -> ISP2 ether1
ISP2 ether0 -> ISP3 ether1

ISP1 ether2 10.100.100.1/24
ISP1 ether3 10.100.200.1/24

ISP2 ether2 10.10.10.1/24
ISP2 ether3 10.10.20.1/24

ISP3 ether2 10.1.1.1/24
ISP3 ether3 10.1.2.1/24


Setup connection

ISP1

/ip address add interface=ether1 address=192.168.1.1/24
/ip address add interface=ether2 address=192.168.3.1/24
/ip address add interface=ether3 address=10.100.100.1/24
/ip address add interface=ether3 address=10.100.200.1/24

ISP2

/ip address add interface=ether1 address=192.168.2.1/24
/ip address add interface=ether2 address=192.168.3.2/24
/ip address add interface=ether3 address=10.10.10.1/24
/ip address add interface=ether4 address=10.10.20.1/24

ISP3

/ip address add interface=ether1 address=192.168.1.2/24
/ip address add interface=ether2 address=192.168.2.2/24
/ip address add interface=ether3 address=10.1.1.1/24
/ip address add interface=ether4 address=10.1.2.1/24

BGP Peering

Consider that IP connectivity between ISPs edge routers and Our Core router is already set up and working properly. So we can start to establish BGP peering to both ISPs.


ISP1:

#set our AS number
/routing bgp instance set default as=10
#add BGP peers
/routing bgp peer
add name=toISP3 remote-address=192.168.1.2 remote-as=30
add name=toISP2 remote-address=192.168.3.2 remote-as=20


ISP2:

#set our AS number
/routing bgp instance set default as=20
#add BGP peers
/routing bgp peer
add name=toISP1 remote-address=192.168.3.1 remote-as=10
add name=toISP3 remote-address=192.168.2.2 remote-as=30

Main / Backup Link Setup di ISP3

ISP3:

Lakukan

  • accept network kita sendiri
  • drop semua tabel IP lainnya, karena kita tidak mau menjadi transit provider
  • BGP AS prepend - menaikan AS path

Outgoing filter ke ISP1:

/routing filter
#accept our networks
add chain=isp1-out prefix=10.1.1.0/24 action=accept
add chain=isp1-out prefix=10.1.2.0/24 action=accept
#discard the rest
add chain=isp1-out action=discard

Outgoing filter ke ISP2:

/routing filter
#accept our networks and prepend AS path three times
add chain=isp2-out prefix=10.1.1.0/24 action=accept set-bgp-prepend=3
add chain=isp2-out prefix=10.1.2.0/24 action=accept set-bgp-prepend=3
#discard the rest
add chain=isp2-out action=discard

ISP1 menjadi main ISP2 menjadi backup

/routing filter
add chain=isp1-in action=discard
add chain=isp2-in action=discard
/ip route
add gateway=192.168.1.1 check-gateway=ping
add gateway=192.168.2.1 distance=30 check-gateway=ping

Cek

/routing filter print
/routing bgp instance print
/routing bgp peer print status
/routing bgp peer print
/routing bgp advertisements print 
/ip route print

Referensi

Pranala Menarik