Use F5:BIGIP to Loadbalance Internet traffic:

Topology diagram:

In this example, We have Two different ISP's with public IP as follows:
ISP1: 50.1.1.1
ISP2: 100.1.1.1

In F5 BIGIP: we create two VIP's for both ISP's
VIP1 for ISP1:50.1.1.20
VIP2 for ISP2: 100.1.1.20

1.Configure ISP Vlan as shown:

2.Create Self IP's for two ISP's as shown:

3.Create Gateway pool by keeping both ISP in it member list.

under health monitors use gateway_icmp

4.Now create a default route pointing towards both the ISP's with next-hop as gateway pool

5.Create a Virtual server list with source address: <any or LAN subnets>

destination address: <any or 0.0.0.0> and apply the Pool to it.

Testing:-