EIGRP Load Balancing.

Eigrp load balance with a variance = 1, meaning that Equal Cost FD is needed
in order to accomplish load balancing. The unequal-cost load-balancing with
EIGRP is subject to one aditional restriction, the  best metric is selected
(FD) and multiplied by the variance, so anything in that range will be used to
load balance over unequal cost path

Sw1#show ip route
Codes: C – connected, S – static, R – RIP, M – mobile, B – BGP
D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area
N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2
E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP
i – IS-IS, su – IS-IS summary, L1 – IS-IS level-1, L2 – IS-IS level-2
ia – IS-IS inter area, * – candidate default, U – per-user static
route
o – ODR, P – periodic downloaded static route

Gateway of last resort is not set

1.0.0.0/24 is subnetted, 2 subnets
C       1.1.17.0 is directly connected, FastEthernet0/1
C       1.1.27.0 is directly connected, FastEthernet0/2
12.0.0.0/32 is subnetted, 1 subnets
D       12.12.12.12 [90/156160] via 1.1.17.1, 00:01:34, FastEthernet0/1
Sw1#
Sw1#
Sw1#
Sw1#
Sw1#
rack10>2
[Resuming connection 2 to R2 … ]

R2#
R2#show ip eigrp inter
IP-EIGRP interfaces for process 1

Xmit Queue   Mean   Pacing Time   Multicast
Pending
Interface        Peers  Un/Reliable  SRTT   Un/Reliable   Flow Timer   Routes
Lo0                0        0/0         0       0/1            0           0
R2#conf te
Enter configuration commands, one per line.  End with CNTL/Z.
R2(config)#do show run int f0/0
Building configuration…

Current configuration : 93 bytes
!
interface FastEthernet0/0
ip address 1.1.27.2 255.255.255.0
duplex auto
speed auto
end

R2(config)#router eigrp 1
R2(config-router)#net 1.1.27.2 0.0.0.0
R2(config-router)#do show ip eigrp inter
IP-EIGRP interfaces for process 1

Xmit Queue   Mean   Pacing Time   Multicast
Pending
Interface        Peers  Un/Reliable  SRTT   Un/Reliable   Flow Timer   Routes
Lo0                0        0/0         0       0/1            0           0
Fa0/0              0        0/0         0       0/1            0           0
R2#
rack10>3
[Resuming connection 3 to cat1 … ]

00:05:48: %DUAL-5
Sw1#
Sw1#show ip route eigrp
12.0.0.0/32 is subnetted, 1 subnets
D       12.12.12.12 [90/156160] via 1.1.27.2, 00:00:04, FastEthernet0/2
[90/156160] via 1.1.17.1, 00:00:04, FastEthernet0/1
Sw1#
Sw1#
Sw1#
Sw1#
Sw1#show ip eigrp topology
IP-EIGRP Topology Table for AS(1)/ID(1.1.27.7)

Codes: P – Passive, A – Active, U – Update, Q – Query, R – Reply,
r – reply Status, s – sia Status

P 12.12.12.12/32, 2 successors, FD is 156160
via 1.1.27.2 (156160/128256), FastEthernet0/2
via 1.1.17.1 (156160/128256), FastEthernet0/1
P 1.1.17.0/24, 1 successors, FD is 28160
via Connected, FastEthernet0/1
P 1.1.27.0/24, 1 successors, FD is 28160
via Connected, FastEthernet0/2
Sw1#! So for example we can modify the default calculation of EIGRP
Sw1#show ip proto | in K
EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0

To configure this in the routers you can use the:
Router(config-router)# metric weights tos k1 k2 k3 k4 k5

using the EIGRP well know formula if K5 is different than 0

metric = [K1*bandwidth + (K2*bandwidth)/(256 – load) + K3*delay] *
[K5/(reliability + K4)]

Sw1#conf te
Enter configuration commands, one per line.  End with CNTL/Z.
Sw1(config)#int f0/2
Sw1(config-if)#band 4
Sw1(config-if)#do show ip route eigrp
12.0.0.0/32 is subnetted, 1 subnets
D       12.12.12.12 [90/156160] via 1.1.17.1, 00:00:01, FastEthernet0/1
Sw1(config-if)#
rack10>1
[Resuming connection 1 to R1 … ]

*Apr 19 21:46:07.92
R1#
R1#show ip eigrp top
IP-EIGRP Topology Table for AS(1)/ID(12.12.12.12)

Codes: P – Passive, A – Active, U – Update, Q – Query, R – Reply,
r – reply Status, s – sia Status

P 12.12.12.12/32, 1 successors, FD is 128256
via Connected, Loopback0
P 1.1.17.0/24, 1 successors, FD is 28160
via Connected, FastEthernet0/0
P 1.1.27.0/24, 1 successors, FD is 640005120
via 1.1.17.7 (640005120/640002560), FastEthernet0/0
R1#

You can also load share over unequal cost paths. To do this we use the
variance feature in the EIGRP routing process. The variance is defined with a
multiplier that represents the difference between the metrics of the paths.
The default variance is ‘1’ which means that the multiple paths must have the
same metrics.

Also we can manipulate the BW + DLY, where the Bw(i) is the min bw and the Dly(i) is the sum of
delay, so for example is we nee to share traffic in 5:1 relationship

post1.jpg

Rack1R1#$rp topology 192.168.1.0 255.255.255.0 | in
(from|bandwidth|delay) 164.1.12.2 (Serial0/0), from 164.1.12.2, Send
flag is 0x0
*Minimum bandwidth is 256 Kbit*
Total delay is 25100 microseconds
164.1.13.3 (Serial0/1), from 164.1.13.3, Send flag is 0x0
*Minimum bandwidth is 256 Kbit*
Total delay is 45100 microseconds

http://www.cisco.com/warp/public/103/eigrp-toc.html

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a008009
437d.shtml#netdiag

Eigrp load balance with a variance = 1, meaning that Equal Cost FD is
needed in order to accomplish load balancing

To get your ratio problem you will need (Composite Metric of R3) *5 =
(Composite Metric of R1)* 1
Need to manipulate the BW or the DLY (by default) to make this happens
{(10e7/minbw + dly/10) * 256} *5 = {(10e7/minbw + dly/10)*256}*1
Since you need that the FDs of the neighbors be in in the variance
factor, in order to do unequal load balancing

Try to clear you Routing Table a couple of time because you are only
installing one path to the destination and the AD from R1 < FD to R3

A Networker Blog

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s