Different GLBP load-balancing methods?

[santiago.jem]

Hi experts,

I was reading and through different first-hop redundancy protocols and thought it's features are great.

Noticed that GLBP offers load-balancing between AVF's and AVG. Load-balancing methods include,

round-robin, host-dependent and weighted.

May I know what would most likely be the result if AVG uses different load-balancing method as to what the AVF's are using?

Hoping to hear from you soon.

Thank you.

Regards,

Jemel

[Giuseppe Larosa · Accepted solution]

Hello Jemel,

load balancing is performed by AVG only when answering to ARP requests from clients for the VIP default gateway.

AVG answers to different clients with the MAC addresses of different working AVFs following one of the load balancing algorithms.

I think that the elected AVG will choice the load balancing algorithm based on its local configuration, and configuration on non AVG devices should not be considered

Hope to help

Giuseppe

[santiago.jem]

Thanks Giuseppe,

This is what I needed to know to cure my curiosity.

Regards,

Jemel

[Reza Sharifi]

Hi,

here are the

LOAD BALANCING OPTIONS

How  network hosts are assigned to each GLBP router can be altered by using  one of four load balancing options outlined below. Please note, these  options are not able to be deployed concurrently. There is a negligible  CPU difference in the operation of either of these options.

1. None

2. Weighted

3. Host dependent

4. Round robin

http://www.cisco.com/en/US/prod/collateral/iosswrel/ps6537/ps6554/ps6600/product_data_sheet0900aecd803a546c.html

HTH

[fawaz Eldiast]

HI Jemel Santiago

LOAD BALANCING OPTIONS:

How network hosts are assigned to each GLBP router can be altered by using one of four load balancing options outlined below. Please note, these

options are not able to be deployed concurrently. There is a negligible CPU difference in the operation of either of these options.

1. None

2. Weighted

3. Host dependent

4. Round robin

NONE

If no load-balance algorithm is specified then GLBP will operate in an identical fashion to HSRP, the AVG will only respond to Address Resolution Protocol (ARP) requests with its own Virtual Forwarder (VF) MAC address, and all traffic will be directed to the AVG with no occurrence of load balancing.

WEIGHTED

This is the ability GLBP to place a weight on each device when calculating the amount of load sharing that will occur through MAC assignment. Each GLBP router in the group will advertise its weighting and assignment; the AVG will act based on that value. For example, if there are two routers in a group and router A has double the forwarding capacity of router B, the weighting value of router A should be configured to be double the amount of router B.

HOST DEPENDENT

The MAC address of a host is used to determine which VF MAC address the host is directed towards. This ensures that a host will be guaranteed to use the same virtual MAC address as long as the number of VFs in the GLBP group is constant.

Host dependent load balancing will need to be used when using statefull Network Address Translation (NAT) because it requires each host to be returned the same virtual MAC address each time it sends an ARP request for the virtual IP address.

Host dependent load balancing is not recommended for situations where there are a small number of end hosts, for example less than 20, unless there is also a requirement that individual hosts must always use the same forwarder. The larger the number of host, the less likely it is to have an imbalance in distribution across forwarders.

This method uses an algorithm designed to equally distribute hosts among forwarders, this distribution changes only when the number for forwarders permanently changes.

ROUND ROBIN

With Round Robin each VF MAC address is used sequentially in ARP replies for the virtual IP address. Round Robin load balancing is suitable for any number of end hosts.