Ada yang masih ingat apa itu BGP Local AS?? Lupa?? oke ndak masalah.. kita akan bahas dari dasar deh.. pertama kita buat dulu topologi seperti ini yaaa
Asumsinya kita udah konfig ip address standard IDN ya.. sekarang tinggal kita konfig BGP nya..
R1(config-router)#do sh run | s r b router bgp 1 bgp log-neighbor-changes network 1.1.1.1 mask 255.255.255.255 neighbor 12.12.12.2 remote-as 2
R2(config-router)#do sh run | s r b router bgp 2 bgp log-neighbor-changes network 2.2.2.2 mask 255.255.255.255 neighbor 12.12.12.1 remote-as 1 neighbor 23.23.23.3 remote-as 3
Sekarang kita coba lihat hasilnya di seluruh router..R3(config-router)#do sh run | s r b router bgp 3 bgp log-neighbor-changes network 3.3.3.3 mask 255.255.255.255 neighbor 23.23.23.2 remote-as 2
R1(config-router)#do sh ip bgp BGP table version is 4, local router ID is 1.1.1.1 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, x best-external, a additional-path, c RIB-compressed, Origin codes: i - IGP, e - EGP, ? - incomplete RPKI validation codes: V valid, I invalid, N Not found Network Next Hop Metric LocPrf Weight Path *> 1.1.1.1/32 0.0.0.0 0 32768 i *> 2.2.2.2/32 12.12.12.2 0 0 2 i *> 3.3.3.3/32 12.12.12.2 0 2 3 i
R2(config-router)#do sh ip bgp BGP table version is 12, local router ID is 2.2.2.2 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, x best-external, a additional-path, c RIB-compressed, Origin codes: i - IGP, e - EGP, ? - incomplete RPKI validation codes: V valid, I invalid, N Not found Network Next Hop Metric LocPrf Weight Path *> 1.1.1.1/32 12.12.12.1 0 0 1 i *> 2.2.2.2/32 0.0.0.0 0 32768 i *> 3.3.3.3/32 23.23.23.3 0 0 3 i
Okeee normal yaa... tabel routing di seluruh router sudah lengkap yaaa...R3(config-router)#do sh ip bgp BGP table version is 12, local router ID is 3.3.3.3 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, x best-external, a additional-path, c RIB-compressed, Origin codes: i - IGP, e - EGP, ? - incomplete RPKI validation codes: V valid, I invalid, N Not found Network Next Hop Metric LocPrf Weight Path *> 1.1.1.1/32 23.23.23.2 0 2 1 i *> 2.2.2.2/32 23.23.23.2 0 0 2 i *> 3.3.3.3/32 0.0.0.0 0 32768 i
Sekarang tiba2 ada sebuah masalah nih di kantor A (AS 1).. Kantor A ternyata berganti AS dari 1 ke 100.. oke kita tinggal ganti AS nya di R1 yaa
Kira2 giaman hasilnya?? tentu saja R1 dan R2 tidak akan adjacency... kenapa?? kan di R2 kita konfignya neighbor 12.12.12.1 remote-as 1 bukan remote-as 100.. sedangkan di R1 AS nya sudah berganti menjadi 100... nah lhoo.. gimana nih?? masak iya saat kantor A berganti AS,kita harus menyuruh kantor lain (AS Lain) mengganti konfigurasi juga?? sepertinya ndak mungkin deh..R1(config)#no router bgp 1 R1(config)#router bgp 100 R1(config-router)#neigh 12.12.12.2 remote-as 2 R1(config-router)#net 1.1.1.1 mask 255.255.255.255
Jadi solusinya, kita bisa menggunakan local AS.. gini nih konfig nya..
nah setelah konfig bgp local-as.. baru deh nda error lagi..R1(config)#router bgp 100 R1(config-router)#neighbor 12.12.12.2 local-as 1
Tuh.. udah adjacency kan antara R1 dan R2.. R1 juga sudah menerima 2 prefix dari R2.. sekarang kita coba cek tabel routing BGP di R1R1(config-router)#do sh ip bgp summ BGP router identifier 1.1.1.1, local AS number 100 BGP table version is 4, main routing table version 4 3 network entries using 444 bytes of memory 3 path entries using 192 bytes of memory 3/3 BGP path/bestpath attribute entries using 408 bytes of memory 2 BGP AS-PATH entries using 48 bytes of memory 0 BGP route-map cache entries using 0 bytes of memory 0 BGP filter-list cache entries using 0 bytes of memory BGP using 1092 total bytes of memory BGP activity 3/0 prefixes, 3/0 paths, scan interval 60 secs Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 12.12.12.2 4 2 10 6 4 0 0 00:01:53 2
nah lhooo.. tau gak kalau sebenarnya disini ada masalah?? coba deh bandingin dengan tabel routing BGP di R1 saat AS nya masih 1..R1(config-router)#do sh ip bgp BGP table version is 4, local router ID is 1.1.1.1 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, x best-external, a additional-path, c RIB-compressed, Origin codes: i - IGP, e - EGP, ? - incomplete RPKI validation codes: V valid, I invalid, N Not found Network Next Hop Metric LocPrf Weight Path *> 1.1.1.1/32 0.0.0.0 0 32768 i *> 2.2.2.2/32 12.12.12.2 0 0 1 2 i *> 3.3.3.3/32 12.12.12.2 0 1 2 3 i
Oke.. ngerti kan bedanya?? pada tabel routing BGP R1 setelah berganti AS.. terdapat AS 1 (AS nya sendiri) pada AS path.. nah untuk mengatasi masalah ini.. kita bisa menggunakan Local AS No Prepend seperti ini ..R1(config-router)#do sh ip bgp BGP table version is 4, local router ID is 1.1.1.1 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, x best-external, a additional-path, c RIB-compressed, Origin codes: i - IGP, e - EGP, ? - incomplete RPKI validation codes: V valid, I invalid, N Not found Network Next Hop Metric LocPrf Weight Path *> 1.1.1.1/32 0.0.0.0 0 32768 i *> 2.2.2.2/32 12.12.12.2 0 0 2 i *> 3.3.3.3/32 12.12.12.2 0 2 3 i
Kita coba cek hasilnya di R1 yaaaR1(config)#router bgp 100 R1(config-router)#nei 12.12.12.2 local-as 1 no-prepend
Oke sudah bener kan.. sekarang AS 1 sudah gak ada di AS Path..R1(config-router)#do sh ip bgp BGP table version is 8, local router ID is 1.1.1.1 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, x best-external, a additional-path, c RIB-compressed, Origin codes: i - IGP, e - EGP, ? - incomplete RPKI validation codes: V valid, I invalid, N Not found Network Next Hop Metric LocPrf Weight Path *> 1.1.1.1/32 0.0.0.0 0 32768 i *> 2.2.2.2/32 12.12.12.2 0 0 2 i *> 3.3.3.3/32 12.12.12.2 0 2 3 i
Oh yaa..kita baru cek tabel routing BGP di R1.. kita belum cek di R2 nih.. coba kita cek yaa.. kira2 ada masalah juga nda ya?? hehe penuh masalah nih kayaknya BGP nya.. hehe
nah lhooo ada masalah juga tuh.. masak R2 kalo pengen ke 1.1.1.1 AS Path nya dobel gitu.. 1 dan 100.. bukannya AS 1 itu AS nya R1 yang lama dan AS 100 itu AS nya R1 yang baru.. kog bisa kedua AS tersebut muncul di AS Path ya.. heheheR2(config-router)#do sh ip bgp BGP table version is 16, local router ID is 2.2.2.2 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, x best-external, a additional-path, c RIB-compressed, Origin codes: i - IGP, e - EGP, ? - incomplete RPKI validation codes: V valid, I invalid, N Not found Network Next Hop Metric LocPrf Weight Path *> 1.1.1.1/32 12.12.12.1 0 0 1 100 i *> 2.2.2.2/32 0.0.0.0 0 32768 i *> 3.3.3.3/32 23.23.23.3 0 0 3 i
Untuk mengatasi masalah ini kita bisa mengkonfigurasikan BGP Local AS No Prepend Replace AS.. materi tersebut akan saya bahas pada lab selanjutnya, lab 126, In Syaa Allah.. Untuk lab ini sampai disini dulu ya.. hehe.. semoga bermanfaat...
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