Multiples routes between 2 subnets/locations

[yoines]

For different reasons, I have to subnets with two alternative routes (2 differens WAN-links). It seems like it is critical if the reply takes another route than the original query.

Is this correct? I though it that doesnt care, which route it takes as long as it reach back to the source.

My idee was to keep the old link in a periode as a failover in case the new link fail.

None of the links have any nat involved

Y

 

[plshlpme]

are they both with the same provider?
thwe problem i believe is that you may take the request on isp1

and then the reply goes to isp2 with a source of your isp1 interface... at which time isp2 says nope im not routing this and drops the packet.

you need to make sure if it comes in isp1 it goes back isp1
and same for isp2...