Dalam BGP route kita memiliki informasi attribut berupa AS mana saja yang dilewati, nah pada lab kali ini kita akan memanipulasi AS-Path dengan menambahkan attribut BGP Prepend yang berfungsi seolah-olah kita menambah lebih banyak path untuk satu route ke network tujuan, kali ini kita akan kembali mempelajari best path selection berdasarkan BGP Prepend
Untuk topologinya seperti ini:
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 100 redistribute-connected=yes
[admin@R1] > routing bgp peer add name=peer1 remote-as=200 remote-address=12.12.12.2
[admin@R1] > routing bgp peer add name=peer2 remote-as=400 remote-address=14.14.14.4
Konfigurasi R2[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 100 redistribute-connected=yes
[admin@R1] > routing bgp peer add name=peer1 remote-as=200 remote-address=12.12.12.2
[admin@R1] > routing bgp peer add name=peer2 remote-as=400 remote-address=14.14.14.4
[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=200 redistribute-connected=yes
[admin@R2] > routing bgp peer add name=peer1 remote-as=100 remote-address=12.12.12.1
[admin@R2] > routing bgp peer add name=peer2 remote-as=300 remote-address=23.23.23.3 in-filter=weight-in
Konfigurasi R3[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=200 redistribute-connected=yes
[admin@R2] > routing bgp peer add name=peer1 remote-as=100 remote-address=12.12.12.1
[admin@R2] > routing bgp peer add name=peer2 remote-as=300 remote-address=23.23.23.3 in-filter=weight-in
[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=300 redistribute-connected=yes
[admin@R3] > routing bgp peer add name=peer1 remote-address=23.23.23.2 remote-as=200
[admin@R3] > routing bgp peer add name=peer2 remote-address=34.34.34.4 remote-as=400
Konfigurasi R4[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=300 redistribute-connected=yes
[admin@R3] > routing bgp peer add name=peer1 remote-address=23.23.23.2 remote-as=200
[admin@R3] > routing bgp peer add name=peer2 remote-address=34.34.34.4 remote-as=400
[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=100 remote-address=14.14.14.1
[admin@R4] > routing bgp peer add name=peer2 remote-as=300 remote-address=34.34.34.3
Selanjutnya lakukan traceroute ke network 4.4.4.0/24 (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=100 remote-address=14.14.14.1
[admin@R4] > routing bgp peer add name=peer2 remote-as=300 remote-address=34.34.34.3
[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% 5 0.9ms 0.9 0.8 0.9 0
2 4.4.4.4 0% 5 1.4ms 1.6 1.1 2.6 0.5
Kita lihat diatas route ke network 4.4.4.0/24 lewat R1, kita akan merubah jalurnya dengan membuat filter dengan action mengubah nilai BGP-Prepend=2 dengan tujuan agar route di prepend(ditunda) 2 kali.# ADDRESS LOSS SENT LAST AVG BEST WORST STD-DEV STATUS
1 12.12.12.1 0% 5 0.9ms 0.9 0.8 0.9 0
2 4.4.4.4 0% 5 1.4ms 1.6 1.1 2.6 0.5
Membuat routing filter :
[admin@R1] > routing filter add chain=prepend-out prefix=4.4.4.0/24 set-bgp-prepend=2
Sekarang kita masukan filtering tadi ke BGP Peer yang mengarah ke R2(12.12.12.2) dari R1
[admin@R1] > routing bgp peer print
Flags: X - disabled, E - established
# INSTANCE REMOTE-ADDRESS REMOTE-AS
0 default 12.12.12.2 200
1 E default 14.14.14.4 400
[admin@R1] > routing bgp peer set numbers=0 out-filter=prepend-out
Sekarang silahkan cek kembali di traceroute pada R2 dan lihat apa yang terjadi jika settingan sudah mengikuti dengan benar route akan berubah melewati R3 (23.23.23.3) karena R1 mangalami pemnambahan AS path/penundaan sehingga seolah olah 2 kali melewat AS (100,100,400).Alhamdulillah postingan kali ini telah selesai, jika artikel ini terasa bermanfaat silahkan bisa di share dengan menekan salah satu button dibawah ini.Flags: X - disabled, E - established
# INSTANCE REMOTE-ADDRESS REMOTE-AS
0 default 12.12.12.2 200
1 E default 14.14.14.4 400
[admin@R1] > routing bgp peer set numbers=0 out-filter=prepend-out
Wassalamu'alaikum ...
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