EIGRP Unequal Load Balancing

Hello everyone,

I'm a bit confuse calculating ratios when it comes to manipulating the bandwidth I hope for someone to help me out. I'm currently doing a lab which includes 3 different paths towards destination network 192.168.10.0/24...The following in the config I have please see if I'm doing it correct:

Interface config from the router that is doing the load balancing:

R7#show run int fa1/0
Building configuration...

Current configuration : 115 bytes
!
interface FastEthernet1/0
bandwidth 100000
ip address 172.16.100.7 255.255.255.0
duplex auto
speed auto
end

R7#

R7#show run int fa2/0
Building configuration...

Current configuration : 113 bytes
!
interface FastEthernet2/0
bandwidth 3831
ip address 172.16.200.7 255.255.255.0
duplex auto
speed auto
end

R7#

R7#show run int s0/0
Building configuration...

Current configuration : 163 bytes
!
interface Serial0/0
bandwidth 963
ip address 172.16.50.7 255.255.255.0
encapsulation frame-relay
serial restart-delay 0
frame-relay interface-dlci 701
end

R7#

++++++++++++++++++++++++++++++++++==

R7#show ip eigrp top 192.168.10.0/24
IP-EIGRP (AS 100): Topology entry for 192.168.10.0/24
State is Passive, Query origin flag is 1, 1 Successor(s), FD is 412160
Routing Descriptor Blocks:
172.16.100.2 (FastEthernet1/0), from 172.16.100.2, Send flag is 0x0
Composite metric is (412160/409600), Route is Internal
Vector metric:
Minimum bandwidth is 10000 Kbit
Total delay is 6100 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 2
172.16.50.1 (Serial0/0), from 172.16.50.1, Send flag is 0x0
Composite metric is (3298304/128256), Route is Internal
Vector metric:
Minimum bandwidth is 963 Kbit
Total delay is 25000 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 1
172.16.200.2 (FastEthernet2/0), from 172.16.200.2, Send flag is 0x0
Composite metric is (824320/409600), Route is Internal
Vector metric:
Minimum bandwidth is 3831 Kbit
Total delay is 6100 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 2
R7#

Below is the traffic shared counts, any idea based on the eigrp topology above WHY I'm still not achieving a 8/4/1 ratio? Thanks in advance.

R7#show ip route 192.168.10.0
Routing entry for 192.168.10.0/24
Known via "eigrp 100", distance 90, metric 412160, type internal
Redistributing via eigrp 100
Last update from 172.16.200.2 on FastEthernet2/0, 00:09:14 ago
Routing Descriptor Blocks:
172.16.200.2, from 172.16.200.2, 00:09:14 ago, via FastEthernet2/0
Route metric is 824320, traffic share count is 1
Total delay is 6100 microseconds, minimum bandwidth is 3831 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 2
* 172.16.100.2, from 172.16.100.2, 00:09:14 ago, via FastEthernet1/0
Route metric is 412160, traffic share count is 2
Total delay is 6100 microseconds, minimum bandwidth is 10000 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 2

R7#

R7#show ip protocol
Routing Protocol is "eigrp 100"
Outgoing update filter list for all interfaces is not set
Incoming update filter list for all interfaces is not set
Default networks flagged in outgoing updates
Default networks accepted from incoming updates
EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0
EIGRP maximum hopcount 100
EIGRP maximum metric variance 8
Redistributing: eigrp 100
EIGRP NSF-aware route hold timer is 240s
Automatic network summarization is not in effect
Maximum path: 4
Routing for Networks:
172.16.50.0/24
172.16.100.0/24
172.16.200.0/24
Routing Information Sources:
Gateway Distance Last Update
172.16.200.2 90 00:18:56
172.16.50.1 90 00:18:56
172.16.100.2 90 00:18:56
Distance: internal 90 external 170

R7#

The goal ratio is 8/4/1, 8 packets on Fa 1/0, 4 packets on Fa 2/0, and 1 packet on Serial 0/0. Formula used:
Worked with the 8/4 ratio in simplified form 1/2...

FD is 412160

412160 x 2 = 824320

10^7/( (824320/256) - (6100/10) ) = BW
10^7/( (3220) - (610) ) = BW
10^7/( 2610 )=3831Kb

Up to this point I have accomplished a 1 to 2 ratio:

R7#show ip route 192.168.10.0
Routing entry for 192.168.10.0/24
Known via "eigrp 100", distance 90, metric 412160, type internal
Redistributing via eigrp 100
Last update from 172.16.200.2 on FastEthernet2/0, 00:09:14 ago
Routing Descriptor Blocks:
172.16.200.2, from 172.16.200.2, 00:09:14 ago, via FastEthernet2/0
Route metric is 824320, traffic share count is 1
Total delay is 6100 microseconds, minimum bandwidth is 3831 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 2
* 172.16.100.2, from 172.16.100.2, 00:09:14 ago, via FastEthernet1/0
Route metric is 412160, traffic share count is 2
Total delay is 6100 microseconds, minimum bandwidth is 10000 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 2

R7#

After adding the 3rd one:

412160 x 8 = 3297280

10^7/( (3297280/256) - (25000/10) ) = BW
10^7/ ( (12880)-(2500) ) = BW
10^7/ ( 10380 ) = 963Kb

Still stuck with a 1 to 2 ratio:

R7#show ip route 192.168.10.0
Routing entry for 192.168.10.0/24
Known via "eigrp 100", distance 90, metric 412160, type internal
Redistributing via eigrp 100
Last update from 172.16.200.2 on FastEthernet2/0, 00:09:14 ago
Routing Descriptor Blocks:
172.16.200.2, from 172.16.200.2, 00:09:14 ago, via FastEthernet2/0
Route metric is 824320, traffic share count is 1
Total delay is 6100 microseconds, minimum bandwidth is 3831 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 2
* 172.16.100.2, from 172.16.100.2, 00:09:14 ago, via FastEthernet1/0
Route metric is 412160, traffic share count is 2
Total delay is 6100 microseconds, minimum bandwidth is 10000 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 2

R7#

Any idea why?

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Comments

Zartanasaurus

Change the variance to 9. The 3rd metric from S0/0 is slightly more than 8x the lowest metric route.

n3twrk0p

It is amazing how one simple mistake could create such problems. Zartanasaurus THANKS A MILLION Mate I've been trying to figure this out for almost a week.

R7#show ip route 192.168.10.0Routing entry for 192.168.10.0/24
Known via "eigrp 100", distance 90, metric 412160, type internal
Redistributing via eigrp 100
Last update from 172.16.200.2 on FastEthernet2/0, 00:00:03 ago
Routing Descriptor Blocks:
172.16.200.2, from 172.16.200.2, 00:00:03 ago, via FastEthernet2/0
Route metric is 824320, traffic share count is 4
Total delay is 6100 microseconds, minimum bandwidth is 3831 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 2
* 172.16.100.2, from 172.16.100.2, 00:00:03 ago, via FastEthernet1/0
Route metric is 412160, traffic share count is 8
Total delay is 6100 microseconds, minimum bandwidth is 10000 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 2
172.16.50.1, from 172.16.50.1, 00:00:03 ago, via Serial0/0
Route metric is 3298304, traffic share count is 1
Total delay is 25000 microseconds, minimum bandwidth is 963 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 1

R7#

Now how you came to the conclusion that the 3rd metric was a little bit off the lowest metric?

Zartanasaurus

The lowest (best) metric is 412,160. EIGRP variance is unforgiving. You must be exactly 8x or less than the lowest metric or you can't ride this ride.
412,160 x 8 is 3,297,280. The metric your router calculated for that 3rd link was 3,298,304. It shows up right there in your show ip eigrp topology.

That metric is higher than the highest metric it will accept with a variance of 8.

Now the traffic share algorithm is forgiving. EIGRP put those 3 routes in the routing table, and the traffic sharing will do some rounding (so to speak) when it determines what share of the traffic to send on a link.

n3twrk0p

I completely nailed this down

Thanks again mate

n3twrk0p

Question,

I'm using the following formula in EIGRP to load balance between 3 links targeting a ratio of 25/18/7:

10^7/((Metric/256)-(Cumulative Delay/10)=BW

Be advise that I'm only manipulating the BANDWIDTH not delay with a FD of 412160 to the target network.

I would like to send 25 packets thru Fa1/0 with a DLY of 6100, 18 Packets thru Fa2/0 same DLY 6100, and 7 Packets thru Serial0/0 DLY 25000.

Could you show me how to achieve a 25/18/7 Ratio? I'm not getting this Ratio.

Thank you

n3twrk0p

Target Ratio 25/18/7 with a FD of 412160 to Destination Network 192.168.10.0/24

In my topology I have 3 interfaces that reach destination network 192.168.10.0/24, they are Fa1/0, Fa2/0 and Serial0/0. I would like to send 25 packets over my Fa1/0, 18 packets thru Fa2/0 and 7 packets thru the Serial 0/0 interface.

Below are the details of these 3 interfaces including bandwidth and delay.

R7#show ip eigrp top 192.168.10.0/24
IP-EIGRP (AS 100): Topology entry for 192.168.10.0/24
State is Passive, Query origin flag is 1, 1 Successor(s), FD is 412160
Routing Descriptor Blocks:
172.16.100.2 (FastEthernet1/0), from 172.16.100.2, Send flag is 0x0
Composite metric is (412160/409600), Route is Internal
Vector metric:
Minimum bandwidth is 10000 Kbit
Total delay is 6100 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 2
172.16.50.1 (Serial0/0), from 172.16.50.1, Send flag is 0x0
Composite metric is (1472000/128256), Route is Internal
Vector metric:
Minimum bandwidth is 3076 Kbit
Total delay is 25000 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 1
172.16.200.2 (FastEthernet2/0), from 172.16.200.2, Send flag is 0x0
Composite metric is (572416/409600), Route is Internal
Vector metric:
Minimum bandwidth is 6150 Kbit
Total delay is 6100 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 2
R7#

I understand that the preferred choice will be the delay when it comes to load share traffic among multiple unequal cost paths due to QoS. But I'm trying to understand the bandwidth manipulation as well not only the delay...Below is my current shared count as you can see is not 25/18/6 but something else.

R7#show ip route 192.168.10.0
Routing entry for 192.168.10.0/24
Known via "eigrp 100", distance 90, metric 412160, type internal
Redistributing via eigrp 100
Last update from 172.16.200.2 on FastEthernet2/0, 00:04:04 ago
Routing Descriptor Blocks:
172.16.200.2, from 172.16.200.2, 00:04:04 ago, via FastEthernet2/0
Route metric is 572416, traffic share count is 173
Total delay is 6100 microseconds, minimum bandwidth is 6150 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 2
* 172.16.100.2, from 172.16.100.2, 00:04:04 ago, via FastEthernet1/0
Route metric is 412160, traffic share count is 240
Total delay is 6100 microseconds, minimum bandwidth is 10000 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 2
172.16.50.1, from 172.16.50.1, 00:04:04 ago, via Serial0/0
Route metric is 1472000, traffic share count is 67
Total delay is 25000 microseconds, minimum bandwidth is 3076 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 1

R7#

Used Variance of 4

R7#show ip protocols
Routing Protocol is "eigrp 100"
Outgoing update filter list for all interfaces is not set
Incoming update filter list for all interfaces is not set
Default networks flagged in outgoing updates
Default networks accepted from incoming updates
EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0
EIGRP maximum hopcount 100
EIGRP maximum metric variance 4
Redistributing: eigrp 100
EIGRP NSF-aware route hold timer is 240s
Automatic network summarization is not in effect
Maximum path: 4
Routing for Networks:
172.16.50.0/24
172.16.100.0/24
172.16.200.0/24
Routing Information Sources:
Gateway Distance Last Update
172.16.200.2 90 00:04:58
172.16.50.1 90 00:04:58
172.16.100.2 90 00:04:58
Distance: internal 90 external 170

R7#

Am I doing an incorrect calculation? Please help me understand WHY am still not getting the Ratio I want for these links...

Thank you and I really appreciate everyone's help on this.