iBGP Update Source Loopback

Kelemahan peering menggunakan physical interface adalah bisa down sewaktu-waktu dan hanya ada 1 route menuju kesana yaitu lewat address interface itu sendiri. Kelebihan menggunakan loopback adalah tidak akan down karena logical interface, kecuali sengaja dishutdown. Selain itu loopback dapat mempunyai banyak route via beberapa physical interface yang diadvertise dalam IGP. Jika ada sebuah physical interface yang down, bisa mencari jalur lain.
Topologi: Masih menggunakan topologi sebelumnya.

Step 1

Buat interface loopback dimasing-masing router kemudian advertise ke OSPF. Agar lebih mudah, hapusjuga BGP 1234 disemua router.

!R1 int lo0 ip add 1.1.1.1 255.255.255.255 ip ospf 10 area 0 !R2 int lo0 ip add 2.2.2.2 255.255.255.255 ip ospf 10 area 0 !R3 int lo0 ip add 3.3.3.3 255.255.255.255 ip ospf 10 area 0 !R4 int lo0 ip add 4.4.4.4 255.255.255.255 ip ospf 10 area 0 R1,R2,R3,R4(config)#no router bgp 1234

Step 2

Konfigurasi iBGP dengan tambahan perintah “neighbor [X.X.X.X] update-source [int loopback]”. Sebelumnya pastikan ip loopback telah reachable via OSPF dan dapat diping.

R1#ping 2.2.2.2 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 2.2.2.2, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 4/5/6 ms R1#ping 3.3.3.3 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 3.3.3.3, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 5/5/6 ms R1#ping 4.4.4.4 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 4.4.4.4, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/5 ms R1(config)#router bgp 1234 R1(config-router)#neighbor 2.2.2.2 remote-as 1234 R1(config-router)#neighbor 2.2.2.2 update-source lo0 R1(config-router)#neighbor 3.3.3.3 remote-as 1234 R1(config-router)#neighbor 3.3.3.3 update-source lo0 R1(config-router)#neighbor 4.4.4.4 remote-as 1234 R1(config-router)#neighbor 4.4.4.4 update-source lo0 R2(config)#router bgp 1234 R2(config-router)#neighbor 1.1.1.1 remote-as 1234 R2(config-router)#neighbor 1.1.1.1 update-source lo0 R2(config-router)#neighbor 3.3.3.3 remote-as 1234 R2(config-router)#neighbor 3.3.3.3 update-source lo0 R2(config-router)#neighbor 4.4.4.4 remote-as 1234 R2(config-router)#neighbor 4.4.4.4 update-source lo0 R3(config)#router bgp 1234 R3(config-router)#neighbor 1.1.1.1 remote-as 1234 R3(config-router)#neighbor 1.1.1.1 update-source lo0 R3(config-router)#neighbor 2.2.2.2 remote-as 1234 R3(config-router)#neighbor 2.2.2.2 update-source lo0 R3(config-router)#neighbor 4.4.4.4 remote-as 1234 R3(config-router)#neighbor 4.4.4.4 update-source lo0 R4(config)#router bgp 1234 R4(config-router)#neighbor 1.1.1.1 remote-as 1234 R4(config-router)#neighbor 1.1.1.1 update-source lo0 R4(config-router)#neighbor 2.2.2.2 remote-as 1234 R4(config-router)#neighbor 2.2.2.2 update-source lo0 R4(config-router)#neighbor 3.3.3.3 remote-as 1234

Lakukan pengecekan.

R3#sh ip bgp sum BGP router identifier 3.3.3.3, local AS number 1234 BGP table version is 2, main routing table version 2 1 network entries using 144 bytes of memory 1 path entries using 60 bytes of memory 1/1 BGP path/bestpath attribute entries using 136 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 340 total bytes of memory BGP activity 1/0 prefixes, 1/0 paths, scan interval 60 secs Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd 1.1.1.1         4         1234       9       6        2    0    0 00:02:01        1 2.2.2.2         4         1234       4       5        2    0    0 00:02:00        0 4.4.4.4         4         1234       5       5        2    0    0 00:01:52        0 R3#sh ip bgp    BGP table version is 2, 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  *>i 11.11.11.11/32   1.1.1.1                  0    100      0 i R3#ping 11.11.11.11 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 11.11.11.11, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/7/19 ms

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