Cisco: BGP Sederhana tanpa filter

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 Ethernet1/2
    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
    network 10.100.200.0
    neighbor 192.168.3.2 remote-as 20
    neighbor 192.168.1.2 remote-as 30
    ! neighbor 192.168.3.2 default-originate 
    ! neighbor 192.168.1.2 default-originate
  end

#set our AS number
/routing bgp instance set default as=10
#add BGP peers
/routing bgp peer
add name=toISP2 remote-address=192.168.3.2 remote-as=20
add name=toISP3 remote-address=192.168.1.2 remote-as=30
# jika ingin redistribute default route ke client yang spesifik
# add name=toISP2 remote-address=192.168.3.2 remote-as=20 default-originate=if-installed
# add name=toISP3 remote-address=192.168.1.2 remote-as=30 default-originate=if-installed

ISP2:

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

ISP3:

enable
configure terminal
  router bgp 30
  bgp router-id 192.168.1.2
    address-family ipv4 unicast
    network 10.1.1.0
    network 10.1.2.0
    neighbor 192.168.1.1 remote-as 10
    neighbor 192.168.2.1 remote-as 20
  end

#set our AS number
/routing bgp instance set default as=30
#add BGP peers
/routing bgp peer
add name=toISP1 remote-address=192.168.1.1 remote-as=10
add name=toISP2 remote-address=192.168.2.1 remote-as=20

Network Advertisements and Routing Filters

Now we can start to advertise our networks and filter out all other unnecessary advertisements.

ISP1:

/routing bgp network
add network=10.100.100.0/24 synchronize=no
add network=10.100.200.0/24 synchronize=no

ISP2:

/routing bgp network
add network=10.10.10.0/24 synchronize=no
add network=10.10.20.0/24 synchronize=no

ISP3:

First step is to advertise our networks

/routing bgp network
add network=10.1.1.0/24 synchronize=no
add network=10.1.2.0/24 synchronize=no

Cek routing

/ip route print

Next step is to specify which routing filter chains will be used

/routing bgp peer
set isp1 in-filter=isp1-in out-filter=isp1-out
set isp2 in-filter=isp2-in out-filter=isp2-out

in-filter is for incoming (received) prefixes, out-filter is for advertised prefixes.

Main/Backup link setup

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

Load sharing setup

Teknik melakukan multihoming / download sharing

ISP3

Disini salah satu network kita di prepend yang berbeda antara ISP1 dan ISP2

Outgoing filter ke ISP1:

/routing filter
#accept our networks and prepend second network
add chain=isp1-out prefix=10.1.1.0/24 action=accept
add chain=isp1-out prefix=10.1.2.0/24 action=accept  set-bgp-prepend=3
#discard the rest
add chain=isp1-out action=discard

Outgoing filter ke ISP2:

/routing filter
#accept our networks and prepend first network
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
#discard the rest
add chain=isp2-out action=discard

Konfigurasi di atas hanya untuk outgoing packet dari network kita. Ada beberapa pilihan,

• biarkan gateway menggunakan konfigurasi main/backup - ini akan menyebabkan hanya satu link yang digunakan dan routing akan asymetric.
• gunakan policy routing untuk memaksa outgoing packet menggunakan link yang sama dengan dengan incoming
• Menggnakan BGP untuk menerima full routing table dari ke dua peer dan menggunakan BGP attribute untuk melakukan routing melalui satu sambungan / link dan sebagian lagi melalui link lainnya. Contoh, traffic local / nasional bisa dikirim menggunakan ISP1 dan Internasional menggunakan ISP2.

Referensi

• https://wiki.mikrotik.com/wiki/Manual:Simple_BGP_Multihoming

Pranala Menarik

• Quagga
• Mikrotik
• Cisco
• Juniper