EIGRP Load Balancing

Load Balancing adalah kemampuan yang dimiliki oleh router untuk membagi trafik ke port yang memiliki metric yang sama menuju network tujuan, semua routing protokol baik RIP, OSPF, EIGRP support untuk equal cost path load balancing, maximum-paths digunakan untuk menentukan maksimun route yang dapat digunakan, tapi EIGRP juga support unequal cost path load balancing dengan mengkonfigurasikan nilai variance. nilai variance n ini memungkinkan router untuk menggunakan route dengan nilai metric sama atau kurang dari metric terkecil dikalikan dengan n. yang perlu diingat adalah unequal load balancing ini hanya bisa menggunakan path / jalur yang menjadi menjadi feasible successor ( AD < FD successor ).

Semua router dikonfigurasikan eigrp,
secara otomatis akan equal load balancing ke network 5.5.5.5 di R5

 R1(config)#do sh ip route eigrp
     35.0.0.0/24 is subnetted, 1 subnets
D       35.35.35.0 [90/307200] via 13.13.13.3, 00:01:30, FastEthernet0/1
     5.0.0.0/32 is subnetted, 1 subnets
D       5.5.5.5 [90/435200] via 13.13.13.3, 00:01:26, FastEthernet0/1
                [90/435200] via 12.12.12.2, 00:01:26, FastEthernet0/0
     25.0.0.0/24 is subnetted, 1 subnets
D       25.25.25.0 [90/307200] via 12.12.12.2, 00:01:26, FastEthernet0/0
     45.0.0.0/24 is subnetted, 1 subnets
D       45.45.45.0 [90/2221056] via 13.13.13.3, 00:01:26, FastEthernet0/1
                   [90/2221056] via 12.12.12.2, 00:01:26, FastEthernet0/0

Unequal Cost Load Balancing                                                                                  

Agar jalurnya tidak sama kita rubah dulu metric salah satu jalurnya,

R1(config)#interface f0/0
R1(config-if)#delay 15000
R1(config-if)#do clear ip route *

Setelah link nya menjadi unequal, jalur yang terpilih di routing tabel adalah yang memiliki metric terkecil

R1#show ip route eigrp
     35.0.0.0/24 is subnetted, 1 subnets
D       35.35.35.0 [90/307200] via 13.13.13.3, 00:00:13, FastEthernet0/1
     5.0.0.0/32 is subnetted, 1 subnets
D       5.5.5.5 [90/435200] via 13.13.13.3, 00:00:14, FastEthernet0/1
     25.0.0.0/24 is subnetted, 1 subnets
D       25.25.25.0 [90/332800] via 13.13.13.3, 00:00:13, FastEthernet0/1
     45.0.0.0/24 is subnetted, 1 subnets
D       45.45.45.0 [90/2221056] via 13.13.13.3, 00:00:14, FastEthernet0/1

Selanjutnya konfigurasikan nilai variance, kita lihat dulu metric masing-masing jalurnya 

 R1#show ip eigrp top 5.5.5.5/32
IP-EIGRP (AS 10): Topology entry for 5.5.5.5/32
  State is Passive, Query origin flag is 1, 1 Successor(s), FD is 435200
  Routing Descriptor Blocks:
  13.13.13.3 (FastEthernet0/1), from 13.13.13.3, Send flag is 0x0
      Composite metric is (435200/409600), Route is Internal
      Vector metric:
        Minimum bandwidth is 10000 Kbit
        Total delay is 7000 microseconds
        Reliability is 255/255
        Load is 1/255
        Minimum MTU is 1500
        Hop count is 2
  12.12.12.2 (FastEthernet0/0), from 12.12.12.2, Send flag is 0x0
      Composite metric is (4249600/409600), Route is Internal
      Vector metric:
        Minimum bandwidth is 10000 Kbit
        Total delay is 156000 microseconds
        Reliability is 255/255
        Load is 1/255
        Minimum MTU is 1500
        Hop count is 2
  14.14.14.4 (Serial1/0), from 14.14.14.4, Send flag is 0x0
      Composite metric is (2809856/2297856), Route is Internal
      Vector metric:
        Minimum bandwidth is 1544 Kbit
        Total delay is 45000 microseconds
        Reliability is 255/255
        Load is 1/255
        Minimum MTU is 1500
        Hop count is 2

nilai variance dapat dicari dengan mudah dengan perhitungan 4249600 :
435200 , hasilnya dibulatkan keatas menjadi 10. 

R1(config)#router eigrp 10
R1(config-router)#variance 10

 R1(config-router)#do show ip route eigrp
     35.0.0.0/24 is subnetted, 1 subnets
D       35.35.35.0 [90/307200] via 13.13.13.3, 00:00:30, FastEthernet0/1
     5.0.0.0/32 is subnetted, 1 subnets
D       5.5.5.5 [90/435200] via 13.13.13.3, 00:00:30, FastEthernet0/1
                [90/4249600] via 12.12.12.2, 00:00:30, FastEthernet0/0
     25.0.0.0/24 is subnetted, 1 subnets
D       25.25.25.0 [90/332800] via 13.13.13.3, 00:00:30, FastEthernet0/1
     45.0.0.0/24 is subnetted, 1 subnets
D       45.45.45.0 [90/2681856] via 14.14.14.4, 00:00:30, Serial1/0
                   [90/2221056] via 13.13.13.3, 00:00:30, FastEthernet0/1
                   [90/6035456] via 12.12.12.2, 00:00:30, FastEthernet0/0

R1(config-router)#do sh ip route 5.5.5.5
Routing entry for 5.5.5.5/32
  Known via "eigrp 10", distance 90, metric 435200, type internal
  Redistributing via eigrp 10
  Last update from 12.12.12.2 on FastEthernet0/0, 00:01:41 ago
  Routing Descriptor Blocks:
  * 13.13.13.3, from 13.13.13.3, 00:01:41 ago, via FastEthernet0/1
      Route metric is 435200, traffic share count is 48
      Total delay is 7000 microseconds, minimum bandwidth is 10000 Kbit
      Reliability 255/255, minimum MTU 1500 bytes
      Loading 1/255, Hops 2
    12.12.12.2, from 12.12.12.2, 00:01:41 ago, via FastEthernet0/0
      Route metric is 4249600, traffic share count is 5
      Total delay is 156000 microseconds, minimum bandwidth is 10000 Kbit
      Reliability 255/255, minimum MTU 1500 bytes
      Loading 1/255, Hops 2

sekarang 2 jalur digunakan semua tapi dengan pembagian trafik yang sesuai.

Kenapa jalur yang melalui R4 tidak digunakan ?
metric dari 14.14.14.2 adalah (2809856/2297856), nilai AD (merah )nya jauh lebih besar dibanding FD successornya 435200.