Lab 15. BGP Local Preference

Assalamu'alaikum Warohmatullahi Wabarokatuh...
baik sahabat configer kali ini saya akan sedikit sharing mengenai BGP Local Preference untuk topologinya seperti ini :

BGP Local preference berfungsi untuk menentukan jalur mana yang akan dipakai untuk trafik data keluar dalam sebuat AS untuk menuju ke network lain, nilai default local preference dari BGP adalan 100, semamkin tinggi nilai nya maka jalur akan semakin di prioritaskan. Jadi kali ini kita akan belajar best path selection berdasarkan local preference.


Oke sekarang kita akan konfigurasikan terlebih dahulu BGP nya

Konfigurasi R1

[admin@MikroTik] > sys id set nam R1
[admin@R1] > ip ad ad ad 12.12.12.1/24 int ether1
[admin@R1] > ip ad ad ad 14.14.14.1/24 int ether2
[admin@R1] > rou bgp in se def as 123 redistribute-connected=yes
[admin@R1] > routing bgp peer add name=peer1 remote-as=123 remote-address=12.12.12.2 nexthop-choice=force-self
[admin@R1] > routing bgp peer add name=peer2 remote-as=400 remote-address=14.14.14.4

Konfigurasi R2

[admin@MikroTik] > sys id set nam R2
[admin@R2] > int br ad nam bridge1
[admin@R2] > ip ad ad ad 12.12.12.2/24 interface=ether1
[admin@R2] > ip ad ad ad 23.23.23.2/24 interface=ether2
[admin@R2] > ip ad ad ad 2.2.2.2/24 interface=bridge1
[admin@R2] > routing bgp instance set default as=123 redistribute-connected=yes
[admin@R2] > routing bgp peer add name=peer1 remote-as=123 remote-address=12.12.12.1
[admin@R2] > routing bgp peer add name=peer2 remote-as=123 remote-address=23.23.23.3

Konfigurasi R3

[admin@MikroTik] > sys id set nam R3
[admin@R3] > ip ad ad ad 23.23.23.3/24 interface=ether1
[admin@R3] > ip ad ad ad 34.34.34.3/24 interface=ether2
[admin@R3] > routing bgp instance set default as=123 redistribute-connected=yes
[admin@R3] > routing bgp peer add name=peer1 remote-address=23.23.23.2 remote-as=123 nexthop-choice=force-self
[admin@R3] > routing bgp peer add name=peer2 remote-address=34.34.34.4 remote-as=400

Konfigurasi R4

[admin@MikroTik] > sys id set nam R4
[admin@R4] > int bridge add name=bridge1
[admin@R4] > ip ad ad ad 4.4.4.4/24 interface=bridge1
[admin@R4] > ip ad ad ad 34.34.34.4/24 interface=ether1
[admin@R4] > ip ad ad ad 14.14.14.4/24 interface=ether2
[admin@R4] > routing bgp instance set default as=400 redistribute-connected=yes
[admin@R4] > routing bgp peer add name=peer1 remote-as=123 remote-address=14.14.14.1
[admin@R4] > routing bgp peer add name=peer2 remote-as=123 remote-address=34.34.34.3

Selanjutnya lakukan traceroute ke network 4.4.4.0/24 (R4) :

[admin@R2] > tool traceroute 4.4.4.4 src-address=2.2.2.2
# ADDRESS     LOSS   SENT   LAST   AVG   BEST   WORST   STD-DEV   STATUS
1 12.12.12.1  0%     4      0.8ms  0.8   0.8    0.9     0
2 4.4.4.4     0%     4      1.2ms  1.5   1.1    2.3     0.5

Kita lihat diatas route ke network 4.4.4.0/24 lewat R1

Local preference dipropagasikan untuk router BGP terluar dari AS ke semua iBGP Peering untuk mengatur trafik keluar dari sebuah AS kali ini kita akan konfigurasi BGP Local Preference di R3 di propagasikan ke R2

[admin@R3] > routing filter add chain=loc-pref-out prefix=4.4.4.0/24 set-bgp-local-pref=150
[admin@R3] > routing bgp peer print detail
Flags: X - disabled, E - established
0 E name="peer1" instance=default remote-address=23.23.23.2 remote-as=123 tcp-md5-key="" nexthop-choice=force-self multihop=no route-reflect=no hold-time=3m
ttl=255 in-filter="" out-filter="" address-families=ip default-originate=never remove-private-as=no as-override=no passive=no use-bfd=no
1 E name="peer2" instance=default remote-address=34.34.34.4 remote-as=400 tcp-md5-key="" nexthop-choice=default multihop=no route-reflect=no hold-time=3m
ttl=255 in-filter="" out-filter="" address-families=ip efault-originate=never remove-private-as=no as-override=no passive=no use-bfd=no
[admin@R3] > routing bgp peer set numbers=0 out-filter=loc-pref-out

sekarang kita cek apakah jalur sudah berubah di R2

[admin@R2] > tool traceroute 4.4.4.4 src-address=2.2.2.2
# ADDRESS LOSS SENT LAST AVG BEST WORST STD-DEV STATUS
1 23.23.23.3 0% 92 0.8ms 0.9 0.5 1.1 0.1
2 4.4.4.4 0% 92 1.2ms 1.4 0.8 2.8 0.3

[admin@R2] > ip route print detail where dst-address 4.4.4.0/24
Flags: X - disabled, A - active, D - dynamic, C - connect, S - static, r - rip, b - bgp, o - ospf, m - mme, B - blackhole, U - unreachable, P - prohibit
[admin@R2] > ip route print detail where dst-address=4.4.4.0/24
Flags: X - disabled, A - active, D - dynamic, C - connect, S - static, r - rip, b - bgp, o - ospf, m - mme, B - blackhole, U - unreachable, P - prohibit
0 ADb dst-address=4.4.4.0/24 gateway=23.23.23.3 gateway-status=23.23.23.3 reachable via ether2 distance=200 scope=40 target-scope=30 bgp-as-path="400" bgp-local-pref=150 bgp-origin=incomplete received-from=peer2

1 Db dst-address=4.4.4.0/24 gateway=12.12.12.1 gateway-status=12.12.12.1 reachable via ether1 distance=200 scope=40 target-scope=30 bgp-as-path="400"
bgp-local-pref=100 bgp-origin=incomplete received-from=peer1

Bisa kita lihat diatas bgl local pref sudah jadi 150. Agar mudah mengingat fungsi dari Local Preference yaitu apabila kita memiliki iBGP lebih dari satu yang Peering dengan eBGP disini kita bisa menggunakannya untuk menentukan lewat mana traffik akan lewat/keluar dari AS.Alhamdulillah postingan kali ini telah selesai, jika artikel ini terasa bermanfaat silahkan bisa di share dengan menekan salah satu button dibawah ini.

Wassalamu'alaikum ...

Share this :