Hi,
Depending on your agreement with provider, you can manage outbound traffic with BGP.
You have 4 subnets in LAN, and 2 providers (so, 2 eBGP connections from WAN router). With the help of route-maps and BGP attributes (let's say local-preference) you announce 2 subnets with a higher priority to the 1st provider and wit lower priority to the 2nd ISP. For the other 2 subnets left, you announce them with higher priority to the 2nd provider and lower priority to the 1st ISP
Just a raw overview of how you should do this:
ip access-list standard FIRST_2_SUBNETS
permit "primary subnet"
permit "secondary subnet"
ip access-list standard LAST_2_SUBNETS
permit "third subnet"
permit "forth subnet"
route-map TO_1ST_ISP permit 10
match ip address FIRST_2_SUBNETS
set local-preference 100
route-map TO_1ST_ISP permit 20
match ip address LAST_2_SUBNETS
set loca-preference 90
route-map TO_2ND_ISP permit 10
match ip address LAST_2_SUBNETS
set local-preference 100
route-map TO_2ND_ISP permit 20
match ip address FIRST_2_SUBNETS
set local-preference 90
router bgp AS_NUMBER
!
neighbor 1ST_ISP_IP remote-as AS_NUMBER_ISP_1
neighbor 1ST_ISP_IP route-map TO_1ST_ISP in
!
neighbor 2ND_ISPF_IP remote-as AS_NUMBER_ISP_2
neighbor 2ND_ISP_IP route-map TO_2ND_ISP in
Some notes here:
-basic concept, you'll have to figure it out the IP addresses and subnets
-you need to have a BGP peering with your ISP providers, or to be able to request one
-this configuration will influence the outbound traffic
-you can also influence inbound traffic (e.g. using as-path prepending) but due to nature of Internet, this may not work as expected
-by default local-preference value is already 100; I just added here to understand this example
I hope you understand my example!
Cheers,
Calin
