Load Balancing

Answered Question
Jan 6th, 2009
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Hi All,

I was hoping someone could help me with a load balancing issue I'm having.


Brief network setup:

Customer has a Point to point serial T1 to our primary datacenter on RTR 2.

Customer has a Frame relay -> ATM T1 to our secondary datacenter.

Primary datacenter is connected secondary via 100mb fiber AND a 1mb ATM PVC. The ATM PVC is on RTR 1 and the Fiber connection is just a Layer 2 connection.


I would like to Load balance downstream traffic across the PTP and FR connections. I've been able to load balance upstream traffic, but downstream isn't being so cooperative.


The included .jpg is a rough sketch of our network with pertinate information including topology, IPs, and interface configs... sanitized of course.

Also included are the show ip eigrp topology output for the desired network (10.220.23.0/24).

If I change the bandwidth statement on the 1mb cross-connect PVC (see diagram), that becomes the primary route for quite a few routes, which is not desired. I'm guessing this is because of the value that's set for delay.

Any thoughts how I could get some downstream load balancing across these circuits?



Correct Answer by Giuseppe Larosa about 8 years 4 months ago

Hello Ryan,


you need to increase delay on the direct link in order to get a chance to load balance


as you can see on the sh ip eigrp topology


10.2.150.2 (ATM2/0.4034), from 10.2.150.2, Send flag is 0x0

Composite metric is (1713920/1709056), Route is Internal

Vector metric:

Minimum bandwidth is 1500 Kbit

Total delay is 290 microseconds

Reliability is 255/255

Load is 1/255

Minimum MTU is 1500

Hop count is 1

10.2.200.1 (ATM2/0.4032), from 10.2.200.1, Send flag is 0x0

Composite metric is (3086080/2226176), Route is Internal

Vector metric:

Minimum bandwidth is 1000 Kbit

Total delay is 20550 microseconds

Reliability is 249/255

Load is 3/255

Minimum MTU is 1500

Hop count is 4


Being



State is Passive, Query origin flag is 1, 1 Successor(s), FD is 1713920


you need to increase delay so that the best metric becomes higher and anothe route can pass the feasibility condition FC


To get a more selective effect on only specific routes you can think to use an offset-list inbound


http://www.cisco.com/en/US/docs/ios/iproute/command/reference/irp_eig2.html#wp1012264


you can define with an IP ACL for what routes the metric has to be modified.


this way you can make two paths comparable.

If they are not equal you can use variance to get load-balancing over them (weighted)


Hope to help

Giuseppe


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Correct Answer
Giuseppe Larosa Tue, 01/06/2009 - 11:32
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Hello Ryan,


you need to increase delay on the direct link in order to get a chance to load balance


as you can see on the sh ip eigrp topology


10.2.150.2 (ATM2/0.4034), from 10.2.150.2, Send flag is 0x0

Composite metric is (1713920/1709056), Route is Internal

Vector metric:

Minimum bandwidth is 1500 Kbit

Total delay is 290 microseconds

Reliability is 255/255

Load is 1/255

Minimum MTU is 1500

Hop count is 1

10.2.200.1 (ATM2/0.4032), from 10.2.200.1, Send flag is 0x0

Composite metric is (3086080/2226176), Route is Internal

Vector metric:

Minimum bandwidth is 1000 Kbit

Total delay is 20550 microseconds

Reliability is 249/255

Load is 3/255

Minimum MTU is 1500

Hop count is 4


Being



State is Passive, Query origin flag is 1, 1 Successor(s), FD is 1713920


you need to increase delay so that the best metric becomes higher and anothe route can pass the feasibility condition FC


To get a more selective effect on only specific routes you can think to use an offset-list inbound


http://www.cisco.com/en/US/docs/ios/iproute/command/reference/irp_eig2.html#wp1012264


you can define with an IP ACL for what routes the metric has to be modified.


this way you can make two paths comparable.

If they are not equal you can use variance to get load-balancing over them (weighted)


Hope to help

Giuseppe


rtjensen4 Thu, 01/08/2009 - 06:23
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Thanks for the reply. I'll give it a go.

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