Different Ways to Load Balance in a Multi-Homed Enterprise Network

[RFS]

Hi,

What are the different techniques to load balance in an enterprise network that is multi-homed with two ISP connections? (Not a primary and fail-over, but both connections being utilized while online and load balancing the traffic).

[balaji.bandi]

Is this for Internal to external (or both)

if Internal to external you can use PBR with IP SLA failover :

I mean :

you can have Subet A  go to ISP-A

you can have Subet B  go to ISP B

If any one of the links fails, the failover takes place automatically to other working ISP (there may be small degradation of service, if they are overloaded).

[RFS]

This is for an internal enterprise network with two external ISP WAN connections.

[RFS]

Question 1: Could BGP be used and would it ever be used in this situation? Or only for a ISP/public internet network?

Question 2: Is it possible to use HSRP to load balance in a private enterprise network with two ISP WAN connections?

Question 3: Any other solutions?

[balaji.bandi]

Are you peering with ISP with BGP, do you have BGP ASN ? what are exciting arrangements with ISP ? or solution in place.

[RFS]

Thank you.

[MHM Cisco World]

If you use BGP 
and you have for example
10.0.0.0-100
we will divide subnet into
10.0.0.0-50 advertise via ISP A
10.0.0.51-100 advertise via ISP B 
this make other site use dual ISP and load balance achieve.

[Richard Burts]

The original poster tells us that "This is for an internal enterprise network with two external ISP WAN connections." and ask some specific questions: 

Question 1: Could BGP be used and would it ever be used in this situation? Or only for a ISP/public internet network?

The answer to the first part is that yes BGP could be used. How well it would fit your particular situation is something that needs to be explored. What IP address space are you using? (private IP addressing or public IP addressing) The ISP probably gave you a Public IP for your router interface, did they also give you a block of addresses to use in your network? What address space would you be advertising to the ISP and how big is it? (advertising a block smaller than /24 is a problem)

Question 2: Is it possible to use HSRP to load balance in a private enterprise network with two ISP WAN connections?

It would be easier to answer this if we knew more about the topology of your network. But basically it should be possible. To accomplish this on each inside interface you configure 2 HSRP groups (resulting in 2 virtual addresses). You configure priority so that the first group is active on routerA and the second group is active on routerB. Then you arrange configuration of the hosts in the subnet so that one group of hosts uses the first virtual IP as their gateway while the other group of hosts uses the second virtual IP as their gateway. This is easy and would work well if the inside hosts are in subnet that connect to the routers that connect to the ISP. It is more of a challenge if the inside network subnets connect to routers which then forward traffic to the network edge routers but still possible.

Question 3: Any other solutions?

Another solution would be to use Policy Based Routing to forward traffic from certain hosts to ISP1 and forward traffic from other hosts to ISP2.

Both HSRP and PBR would have the network edge routers translate inside addresses to a Public IP and forward to ISP and avoid any complications about what address space you would advertise to the ISP.