11-06-2008 04:32 AM - edited 03-04-2019 12:13 AM
Hi
We have topology
LP ----- ET1
|
|
ET2
Where LP is the CORE 6500 and the ET1/ET2 connected to it via EIGRP.As per customer the load balancing is not happening between LP and ET1/ET2.He is seeing only the LP to ET1 is utilized all the time.
I had attached the config for your refference
Pls let me know ur suggestions
11-06-2008 04:44 AM
Hello Madan,
with default K values EIGRP metric is proportional to:
256 * sum (Delays on the path in tens of microsec)
+
256 * 10^7/(lowest BW in the path)
However,
in your case you have modified the bandwidth from LP to ET2 :
interface GigabitEthernet5/6
description ### link betw LP & ET###
no switchport
bandwidth 10240
while link from LP to ET1 has default values:
interface GigabitEthernet5/4
description ### link betw LP & ET###
no switchport
ip address 10.212.176.21 255.255.255.252
routing protocol uses outgoing interface parameters so LP prefers the path via ET1.
to get load-balancing:
or remove bandwidth 10240 in int g5/6 or add it to g5/4
Hope to help
Giuseppe
11-06-2008 10:07 AM
If you have the bandwidth configured this way for a reason, You can also use the eigrp variance command for unequal cost load balancing
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a008009437d.shtml
11-07-2008 04:34 AM
or use the "variance" command
11-06-2008 06:18 PM
By default EIGRP uses bandwidth and delay to calculate it's metric. In the configuration given, the bandwidth on the interface GigabitEthernet5/6 connecting to ET2 is configured to 10240 kilobits.
If the same routes are advertised by ET1 and ET2. LP will always prefer the routes via ET1 because of the better metric.
In your case,configure unequal cost load balancing using the variance command on LP to load balance across ET1 and ET2.
Using the show ip eigrp topology, you'll see the metrics for the routes advertised by ET1 and ET2. For example, if the metric advertised by ET1 is 20 and that by ET2 is 40 for a route. Using variance 2, the minimum metric now becomes (20 x 2)=40. LP will now choose ET2 and ET1 to get to the route. I hope you the get the idea.
Lejoe
11-06-2008 10:44 PM
Hi
Thank u all for ur inputs will rate each one of ur postings once i implement this.
As per the customer the ET1 is having 10 mb link and the ET2 is having 20 MB link
should i add variance 2/traffic-share balanced under EIGRP i think that will take care of loadbalancing
Please find the ouputs of
sh ip eigrp topology / sh ip route eigrp pls refer and suggest
lp#sh ip eigrp topology
IP-EIGRP Topology Table for AS(1)/ID(10.212.176.21)
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status
P 10.212.177.32/27, 1 successors, FD is 2816
via Connected, Vlan12
P 10.212.190.0/24, 1 successors, FD is 28672
via 10.212.176.22 (28672/28416), GigabitEthernet5/4
via 10.212.176.18 (252928/28416), GigabitEthernet5/6
P 10.212.187.0/24, 1 successors, FD is 26368
via 10.212.176.22 (26368/26112), GigabitEthernet5/4
via 10.212.176.18 (250624/26112), GigabitEthernet5/6
P 10.212.182.0/24, 1 successors, FD is 2816
via Connected, Vlan114
P 10.212.183.0/24, 1 successors, FD is 2816
via Connected, Vlan102
P 10.212.180.0/23, 1 successors, FD is 2816
via Connected, Vlan16
P 10.212.178.0/24, 1 successors, FD is 2816
via Connected, Vlan100
P 10.212.179.0/24, 1 successors, FD is 2816
via Connected, Vlan101
P 10.212.176.0/29, 1 successors, FD is 2816
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status
via Connected, Vlan1
P 10.212.176.0/22, 1 successors, FD is 2816
via Summary (2816/0), Null0
P 10.212.177.0/27, 1 successors, FD is 2816
via Connected, Vlan11
P 10.212.168.0/22, 1 successors, FD is 26112
via 10.212.176.22 (26112/2816), GigabitEthernet5/4
via 10.212.176.18 (250368/2816), GigabitEthernet5/6
P 10.212.176.20/30, 1 successors, FD is 25856
via Connected, GigabitEthernet5/4
P 10.212.176.16/30, 1 successors, FD is 250112
via Connected, GigabitEthernet5/6
P 10.212.160.0/26, 1 successors, FD is 26112
via 10.212.176.22 (26112/2816), GigabitEthernet5/4
via 10.212.176.18 (250368/2816), GigabitEthernet5/6
P 10.212.177.192/26, 1 successors, FD is 2816
via Connected, Vlan14
P 10.212.11.0/24, 1 successors, FD is 26368
via 10.212.176.22 (26368/26112), GigabitEthernet5/4
via 10.212.176.18 (250624/26112), GigabitEthernet5/6
P 10.212.0.0/22, 1 successors, FD is 26112
via 10.212.176.22 (26112/2816), GigabitEthernet5/4
via 10.212.176.18 (250368/2816), GigabitEthernet5/6
P 10.212.177.128/26, 1 successors, FD is 2816
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status
via Connected, Vlan13
P 199.49.11.0/24, 1 successors, FD is 28672
via 10.212.176.22 (28672/28416), GigabitEthernet5/4
via 10.212.176.18 (252928/28416), GigabitEthernet5/6
lp#sh ip route eigrp
D EX 199.49.11.0/24 [170/28672] via 10.212.176.22, 1d03h, GigabitEthernet5/4
10.0.0.0/8 is variably subnetted, 22 subnets, 8 masks
D EX 10.212.190.0/24
[170/28672] via 10.212.176.22, 1d03h, GigabitEthernet5/4
D 10.212.187.0/24
[90/26368] via 10.212.176.22, 1d03h, GigabitEthernet5/4
D 10.212.168.0/22
[90/26112] via 10.212.176.22, 1d03h, GigabitEthernet5/4
D 10.212.160.0/26
[90/26112] via 10.212.176.22, 1d03h, GigabitEthernet5/4
D 10.212.11.0/24 [90/26368] via 10.212.176.22, 1d03h, GigabitEthernet5/4
D 10.212.0.0/22 [90/26112] via 10.212.176.22, 1d03h, GigabitEthernet5/4
Regards
Madan
11-06-2008 11:50 PM
Madan,
You need to set the variance to be a value of atleast 10. If you check the show IP EIGRP topology below :
P 10.212.168.0/22, 1 successors, FD is 26112
via 10.212.176.22 (26112/2816), GigabitEthernet5/4
via 10.212.176.18 (250368/2816), GigabitEthernet5/6
You FD is 26112 which is the best metric to reach that destination. Now the same destination via Gig5/6 neighbor is reachable with a metric of 250368. If you want to make this path to be used for unequal cost-path load balancing you have to divide 250368 with the FD 26112 which comes around 10 taking into account the other routes in the EIGRP topology.
HTH, Please rate if it does.
-amit singh
11-07-2008 03:01 AM
From sh ip eigrp topology
Following are the subnets for which you need unequal cost load balancing.
P 10.212.190.0/24, 1 successors, FD is 28672
via 10.212.176.22 (28672/28416), GigabitEthernet5/4
via 10.212.176.18 (252928/28416), GigabitEthernet5/6
P 10.212.187.0/24, 1 successors, FD is 26368
via 10.212.176.22 (26368/26112), GigabitEthernet5/4
via 10.212.176.18 (250624/26112), GigabitEthernet5/6
P 10.212.168.0/22, 1 successors, FD is 26112
via 10.212.176.22 (26112/2816), GigabitEthernet5/4
via 10.212.176.18 (250368/2816), GigabitEthernet5/6
P 10.212.160.0/26, 1 successors, FD is 26112
via 10.212.176.22 (26112/2816), GigabitEthernet5/4
via 10.212.176.18 (250368/2816), GigabitEthernet5/6
P 10.212.11.0/24, 1 successors, FD is 26368
via 10.212.176.22 (26368/26112), GigabitEthernet5/4
via 10.212.176.18 (250624/26112), GigabitEthernet5/6
P 10.212.0.0/22, 1 successors, FD is 26112
via 10.212.176.22 (26112/2816), GigabitEthernet5/4
via 10.212.176.18 (250368/2816), GigabitEthernet5/6
P 199.49.11.0/24, 1 successors, FD is 28672
via 10.212.176.22 (28672/28416), GigabitEthernet5/4
via 10.212.176.18 (252928/28416), GigabitEthernet5/6
********
Taking one subnet as an example
P 10.212.190.0/24, 1 successors, FD is 28672
via 10.212.176.22 (28672/28416), GigabitEthernet5/4
via 10.212.176.18 (252928/28416), GigabitEthernet5/6
We can see the metric advertised through Gig 5/4 is 28672 and that by Gig 5/6 252928
Smallest metric = 28672
To find variance value
252928/28672 = 8.8 approx 9
Hence, variance value is 9. Just do the above calculation for the subnets to obtain the variance value. As Amit, has suggested, it will be approximately 10. Once unequal cost load balancing is configured, you should see two next hops for the above subnets in the routing table.
Lejoe
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