Cisco: BGP 2 link ke 3 BGP redistribute 2 OSPF

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 

R4

IP 10.1.1.2/24 menuju ISP3
IP 172.16.1.1  menuju R5
IP 172.16.10.1 LAN
IP 172.16.20.1 LAN

R5

IP 10.1.2.2/24 menuju ISP3
IP 172.16.1.2  menuju R4
IP 172.16.100.1/24 LAN
IP 172.16.200.1/24 LAN

Sambungan Fisik

ISP1

ISP1 Eth1/0 -> ISP3 Eth1/0
ISP1 Eth1/1 -> ISP2 Eth1/1
ISP2 Eth1/0 -> ISP3 Eth1/1

ISP1 Eth1/2 10.100.100.1/24
ISP1 Eth1/3 10.100.200.1/24

ISP2 Eth1/2 10.10.10.1/24
ISP2 Eth1/3 10.10.20.1/24

ISP3 Eth1/2 10.1.1.1/24
ISP3 Eth1/3 10.1.2.1/24

Setup connection

ISP1

enable
configure terminal
  interface Ethernet1/0
    ip address 192.168.1.1 255.255.255.0
    no shutdown
    exit
  interface Ethernet1/1
    ip address 192.168.3.1 255.255.255.0
    no shutdown
    exit
  interface Ethernet1/2
    ip address 10.100.100.1 255.255.255.0
    no shutdown
    exit
  interface Ethernet1/3
    ip address 10.100.200.1 255.255.255.0
    no shutdown
    exit
 end

ISP2

enable
configure terminal
  interface Ethernet1/0
    ip address 192.168.2.1 255.255.255.0
    no shutdown
    exit
  interface Ethernet1/1
    ip address 192.168.3.2 255.255.255.0
    no shutdown
    exit
  interface Ethernet1/2
    ip address 10.10.10.1 255.255.255.0
    no shutdown
    exit
  interface Ethernet1/3
    ip address 10.10.20.1 255.255.255.0
    no shutdown
    exit
 end

ISP3

enable
configure terminal
  interface Ethernet1/0
    ip address 192.168.1.2 255.255.255.0
    no shutdown
    exit
  interface Ethernet1/1
    ip address 192.168.2.2 255.255.255.0
    no shutdown
    exit
  interface Ethernet1/2
    ip address 10.1.1.1 255.255.255.0
    no shutdown
    exit
  interface Ethernet1/3
    ip address 10.1.2.1 255.255.255.0
    no shutdown
    exit
 end

R4

enable
configure terminal
  interface Ethernet1/0
    ip address 10.1.1.2 255.255.255.0
    no shutdown
    exit
  interface Ethernet1/1
    ip address 172.16.1.1 255.255.255.0
    no shutdown
    exit
  interface Ethernet1/2
    ip address 172.16.10.1 255.255.255.0
    no shutdown
    exit
  interface Ethernet1/3
    ip address 172.16.20.1 255.255.255.0
    no shutdown
    exit
 end

R5

enable
configure terminal
  interface Ethernet1/0
    ip address 10.1.2.2 255.255.255.0
    no shutdown
    exit
  interface Ethernet1/1
    ip address 172.16.1.2 255.255.255.0
    no shutdown
    exit
  interface Ethernet1/2
    ip address 172.16.100.1 255.255.255.0
    no shutdown
    exit
  interface Ethernet1/3
    ip address 172.16.200.1 255.255.255.0
    no shutdown
    exit
 end

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:

enable
configure terminal
  router bgp 10
  bgp router-id 192.168.1.1
    ! address-family ipv4 unicast 
    network 10.100.100.0 mask 255.255.255.0
    network 10.100.200.0 mask 255.255.255.0
    neighbor 192.168.3.2 remote-as 20
    neighbor 192.168.1.2 remote-as 30
    neighbor 192.168.3.2 activate 
    neighbor 192.168.1.2 activate 
    ! neighbor 192.168.3.2 default-originate 
    ! neighbor 192.168.1.2 default-originate
  end

ISP2:

enable
configure terminal
  router bgp 20
  bgp router-id 192.168.2.1
    ! address-family ipv4 unicast
    network 10.10.10.0 mask 255.255.255.0
    network 10.10.20.0 mask 255.255.255.0
    neighbor 192.168.3.1 remote-as 10
    neighbor 192.168.2.2 remote-as 30
    neighbor 192.168.3.1 activate 
    neighbor 192.168.2.2 activate 
  end

Main / Backup Link Setup di ISP3

Lakukan

• accept network kita sendiri
• drop semua tabel IP lainnya, karena kita tidak mau menjadi transit provider
• BGP AS prepend - menaikan AS path ke salah satu ISP (disini ISP1)

ISP3:

enable
configure terminal
  router bgp 30
  bgp router-id 192.168.1.2
    no synchronization
    bgp log-neighbor-changes
    network 10.1.1.0 mask 255.255.255.0
    network 10.1.2.0 mask 255.255.255.0
    neighbor 192.168.1.1 remote-as 10
    neighbor 192.168.2.1 remote-as 20
    neighbor 192.168.1.1 activate
    neighbor 192.168.2.1 activate 
    redistribute ospf 3 metric 100 
  end

OSPF

ISP3

enable
configure terminal
 !
 ! area 0 = backbone
 router ospf 3
 network 10.1.1.0 0.0.0.255 area 0.0.0.0
 network 10.1.2.0 0.0.0.255 area 0.0.0.0
 !
 ! redistribute routing BGP
 redistribute bgp 30 subnets
 end

R4

enable
configure terminal
 !
 ! area 0 = backbone
 router ospf 4
 network 10.1.1.0 0.0.0.255 area 0.0.0.0
 network 172.16.1.0 0.0.0.255 area 0.0.0.0
 network 172.16.10.0 0.0.0.255 area 0.0.0.0
 network 172.16.20.0 0.0.0.255 area 0.0.0.0
 end

R5

enable
configure terminal
  !
  ! area 0 = backbone
  router ospf 5
  network 10.1.2.0 0.0.0.255 area 0.0.0.0
  network 172.16.1.0 0.0.0.255 area 0.0.0.0
  network 172.16.100.0 0.0.0.255 area 0.0.0.0
  network 172.16.200.0 0.0.0.255 area 0.0.0.0
  end

Cek

! perhatikan AS 30 di tambahkan 5x ke routing ke arah AS 10
!
show ip bgp

show ip route
show ip bgp 10.100.1000.0/24
show ip bgp neighbors 192.168.2.2 advertised-routes
show ip bgp neighbor 192.168.1.1 routes
show bgp ipv4 unicast neighbors 
show bgp ipv4 unicast summary

Referensi

• https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bgp/configuration/xe-16/irg-xe-16-book/configuring-a-basic-bgp-network.html
• https://wiki.mikrotik.com/wiki/Manual:Simple_BGP_Multihoming

Pranala Menarik

• TCP/IP: Advanced Routing
• Quagga
• Mikrotik
• Cisco
• Juniper
• BIRD: Routing
• IPv6