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Belajar mengkonfigurasi BGP (AS_PATH)

Topology yang digunakan adalah sebagai berikut:
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Pada skenario ini kita ingin belajar mengkonfigurasi router cnc3
sehingga dapat mempengaruhi pemilihan path AS 500, defaultnya router
dari AS 500 mempunyai jalur ke network 192.168.30.0/24 melalui 2 jalur,
pertama melewati AS 100 dengan AS_PATH attribute (100,200,300 )dan
melewati AS 400 dengan AS_PATH attribute (400,300), dan secara default
AS 500 akan memilih “shortest AS_PATH” yaitu (400,300)
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cnc5#ping 192.168.30.1 source 192.168.20.1 repeat 100

Type escape sequence to abort.
Sending 100, 100-byte ICMP Echos to 192.168.30.1, timeout is 2 seconds:
Packet sent with a source address of 192.168.20.1
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Success rate is 100 percent (100/100), round-trip min/avg/max = 96/192/448 ms
cnc5#
———————————————————————
cnc5#traceroute 192.168.30.1 source 192.168.20.1

Type escape sequence to abort.
Tracing the route to 192.168.30.1

1 192.168.10.2 152 msec 1228 msec 624 msec
2 192.168.10.17 316 msec 232 msec *
cnc5#
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nah sekarang kita ingin memanipulasi router cnc3 agar path AS 500,
ketika ingin ke network 192.168.30.0/24 akan melalui jalur AS 100
dengan AS_PATH atrribute (100,200,300) sedangkan AS_PATH attribute
jalur AS 400 menjadi (400,300,300,300) sehingga dipilih jalur AS_PATH 100,
karena memiliki “shortest AS_PATH”
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cnc3(config)#router bgp 300
cnc3(config-router)#neighbor 192.168.10.18 route-map iwingpath out
cnc3(config-router)#exit
cnc3(config)#route-map iwingpath permit 10
cnc3(config-route-map)#set as-path prepend 300 300
!perintah ini memerintahkan local router untuk menambahkan ASN 300 dua
!kali sebelum dikirimkan ke neighbour 192.168.10.18
cnc3(config-route-map)#
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Hasilnya adalah sebagai berikut
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cnc5#sh ip bgp 192.168.30.1
BGP routing table entry for 192.168.30.0/24, version 9
Paths: (2 available, best #1, table Default-IP-Routing-Table)
Flag: 0x820
Advertised to update-groups:
1
100 200 300
192.168.10.6 from 192.168.10.6 (192.168.10.9)
Origin IGP, localpref 100, valid, external, best
400 300 300 300
192.168.10.2 from 192.168.10.2 (192.168.10.18)
Origin IGP, localpref 100, valid, external
cnc5#
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cnc5#ping 192.168.30.1 source 192.168.20.1 repeat 100

Type escape sequence to abort.
Sending 100, 100-byte ICMP Echos to 192.168.30.1, timeout is 2 seconds:
Packet sent with a source address of 192.168.20.1
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Success rate is 100 percent (100/100), round-trip min/avg/max = 96/202/568 ms
cnc5#
———————————————————————
cnc5#traceroute 192.168.30.1 source 192.168.20.1

Type escape sequence to abort.
Tracing the route to 192.168.30.1

1 192.168.10.6 128 msec 108 msec 72 msec
2 192.168.10.10 216 msec 196 msec 124 msec
3 192.168.10.14 212 msec 172 msec *
cnc5#
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Selamat mencoba, maaf kalau penjelasannya ga jelas xahahahaha……..

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