BGP Lab 12 : BGP Multihoming 2 ISP Berbeda

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LAB 12

 



Untuk topologynya berubah sedikit dan konfigurasi peeringnya otomatis juga berubah, hapus terlebih dahulu konfig bgp pada semua router.

R1

R1(config)#no router bgp 1

R2

R2(config)#no router bgp 23

R3

R3(config)#no router bgp 23

R4

R4(config)#no router bgp 4

Kita konfigurasi BGP kembali pada semua router

R1

R1(config)#router bgp 1

R1(config-router)#network 1.1.1.1 mask 255.255.255.255

R1(config-router)#neighbor 12.12.12.2 remote-as 2

R1(config-router)#neighbor 13.13.13.3 remote-as 3

R1(config-router)#maximum-paths 2

R2

R2(config)#router bgp 2
R2(config-router)#neighbor 12.12.12.1 remote-as 1
R2(config-router)#neighbor 24.24.24.4 remote-as 4

R3

R3(config)#router bgp 3
R3(config-router)#neighbor 13.13.13.1 remote-as 1
R3(config-router)#neighbor 34.34.34.4 remote-as 4

R4

R4(config)#router bgp 4
R4(config-router)#network 4.4.4.4 mask 255.255.255.255
R4(config-router)#neighbor 24.24.24.2 remote-as 2
R4(config-router)#neighbor 34.34.34.3 remote-as 3

R1

R1#sh ip bgp
Network Next Hop Metric LocPrf Weight Path
*> 1.1.1.1/32 0.0.0.0 0 32768 i
*> 4.4.4.4/32 12.12.12.2 0 2 4 i
* 13.13.13.3 0 3 4 i

R1#sh ip route 4.4.4.4
Routing entry for 4.4.4.4/32
Known via "bgp 1", distance 20, metric 0
Tag 2, type external
Last update from 12.12.12.2 00:11:11 ago
Routing Descriptor Blocks:
* 12.12.12.2, from 12.12.12.2, 00:11:11 ago
Route metric is 0, traffic share count is 1
AS Hops 2
Route tag 2

R1#traceroute 4.4.4.4 source 1.1.1.1
Type escape sequence to abort.
Tracing the route to 4.4.4.4
1 12.12.12.2 4 msec 40 msec 8 msec
2 24.24.24.4 56 msec 44 msec 32 msec

Bisa dilihat bahwa walaupun sudah dikonfigurasikan maxium-path 2 namun tetap saja tidak load sharing, melainkan hanya berfungsi sebagai main backup saja. Agar bisa load sharing melalui 2 ISP berbeda gunakan sebagai berikut.

R1

R1(config)#router bgp 1
R1(config-router)#bgp bestpath as-path multipath-relax
R1(config-router)#do clear ip bgp *

R1(config)#do show ip bgp
Network Next Hop Metric LocPrf Weight Path
*> 1.1.1.1/32 0.0.0.0 0 32768 i
* 4.4.4.4/32 13.13.13.3 0 3 4 i
*> 12.12.12.2 0 2 4 i

R1(config)#do show ip route 4.4.4.4
Routing entry for 4.4.4.4/32
Known via "bgp 1", distance 20, metric 0
Tag 2, type external
Last update from 12.12.12.2 00:06:26 ago
Routing Descriptor Blocks:
* 13.13.13.3, from 13.13.13.3, 00:06:26 ago
Route metric is 0, traffic share count is 1
AS Hops 2
Route tag 2
12.12.12.2, from 12.12.12.2, 00:06:26 ago
Route metric is 0, traffic share count is 1
AS Hops 2
Route tag 2

R1#traceroute 4.4.4.4 source 1.1.1.1
Type escape sequence to abort.
Tracing the route to 4.4.4.4
1 12.12.12.2 40 msec
13.13.13.3 28 msec
12.12.12.2 20 msec
2 34.34.34.4 40 msec
24.24.24.4 32 msec
34.34.34.4 44 msec

Nah sekarang sudah load sharing. Saat ini permasalahannya adalah seadainya bandwidth antara kedua link tersebut adalah berbeda, maka bagaimana proses sharing antar kedua link tersebut bisa berjalan.

R1

R1(config)#int g1/0
R1(config-if)#bandwidth 1000
R1(config-if)#int g2/0
R1(config-if)#bandwidth 2000
R1(config-if)#do clear ip bgp * soft

R1(config)#do show ip bgp
BGP table version is 6, 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
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 1.1.1.1/32 0.0.0.0 0 32768 i
* 4.4.4.4/32 13.13.13.3 0 3 4 i
*> 12.12.12.2 0 2 4 i

R1(config)#do show ip route 4.4.4.4
Routing entry for 4.4.4.4/32
Known via "bgp 1", distance 20, metric 0
Tag 2, type external
Last update from 12.12.12.2 00:18:51 ago
Routing Descriptor Blocks:
* 13.13.13.3, from 13.13.13.3, 00:18:51 ago
Route metric is 0, traffic share count is 2
AS Hops 2
Route tag 2
12.12.12.2, from 12.12.12.2, 00:18:51 ago
Route metric is 0, traffic share count is 1
AS Hops 2
Route tag 2

Lalu cek kembali

R1

R1(config)#do show ip route 4.4.4.4
Routing entry for 4.4.4.4/32
Known via "bgp 1", distance 20, metric 0
Tag 2, type external
Last update from 12.12.12.2 00:25:22 ago
Routing Descriptor Blocks:
* 13.13.13.3, from 13.13.13.3, 00:25:22 ago
Route metric is 0, traffic share count is 1
AS Hops 2
Route tag 2
12.12.12.2, from 12.12.12.2, 00:25:22 ago
Route metric is 0, traffic share count is 1
AS Hops 2
Route tag 2

Setelah kita lihat, ternyata masih 1:1 padahal bandwidthnya berbeda. Hal ini tentunya akan memunculkan permasalahan, terutama apabila link satu dengan link lain bandiwidthnya terpaut jauh. Sehingga perlu kita konfigurasikan sebagai berikut

R1

R1(config)#router bgp 1
R1(config-router)#bgp dmzlink-bw
R1(config-router)#neighbor 12.12.12.2 dmzlink-bw
R1(config-router)#neighbor 13.13.13.3 dmzlink-bw
R1(config-router)#do clear ip bgp * soft

R1(config)#do show ip bgp
BGP table version is 6, 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
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 1.1.1.1/32 0.0.0.0 0 32768 i
* 4.4.4.4/32 13.13.13.3 0 3 4 i
*> 12.12.12.2 0 2 4 i

R1(config)#do show ip route 4.4.4.4
Routing entry for 4.4.4.4/32
Known via "bgp 1", distance 20, metric 0
Tag 2, type external
Last update from 12.12.12.2 00:18:51 ago
Routing Descriptor Blocks:
* 13.13.13.3, from 13.13.13.3, 00:18:51 ago
Route metric is 0, traffic share count is 2
AS Hops 2
Route tag 2
12.12.12.2, from 12.12.12.2, 00:18:51 ago
Route metric is 0, traffic share count is 1
AS Hops 2
Route tag 2

Seperti yang terlihat bahwa sekarang load sharingnya sudah dalam perbandingan yang baik, sehingga kedua link tersebut bisa digunakan sesuai kemampuannya.

R1

R1#traceroute 4.4.4.4 source 1.1.1.1
Type escape sequence to abort.
Tracing the route to 4.4.4.4
1 12.12.12.2 56 msec
13.13.13.3 40 msec 24 msec
2 24.24.24.4 36 msec
34.34.34.4 32 msec 36 msec



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