Cisco: BGP Dua Link main backup - dengan set community

CATATAN: harus di oprek lagi, belum bener propagasi weight-nya

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 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

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:

! AS kita 30, set preference yang berbeda untuk masing2 uplink
!
!    200: set local preference to 200 (via AS 20)
!    500: set local preference to 500 (via AS 10)
!
configure terminal
 ip bgp-community new-format
 router bgp 30
  neighbor 192.168.2.1 remote-as 20
  neighbor 192.168.2.1 next-hop-self
  neighbor 192.168.2.1 send-community
  neighbor 192.168.1.1 remote-as 10
  neighbor 192.168.1.1 next-hop-self
  neighbor 192.168.1.1 send-community
end
!
configure terminal
  route-map LOCAL_PREF_200 permit 10
  set community 20:200
  route-map LOCAL_PREF_500 permit 10
  set community 10:500
end
!
configure terminal
 ! tambahkan route map ke masing-masing neighbor
 !
 router bgp 30
   neighbor 192.168.2.1 route-map LOCAL_PREF_200 out
   neighbor 192.168.1.1 route-map LOCAL_PREF_500 out
 end

configure terminal
 ! advertise network di belakang router
 !
 router bgp 30
   network 10.1.1.0 mask 255.255.255.0
   network 10.1.2.0 mask 255.255.255.0
 end

Cek

! perhatikan AS 30 di tambahkan 5x ke routing ke arah AS 10
!
clear ip bgp 10
clear ip bgp 20
!
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

• http://evilrouters.net/2009/03/18/using-bgp-communities-to-influence-routing/
• http://evilrouters.net/2009/03/20/allowing-customers-to-manipulate-routing-using-bgp-communities/
• 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