I have a question about a double WAN setup. I hope this will be intelligible. I have router1 plugged into ISP1 on its eth1 and router2 plugged into ISP2 over its eth1. Between these 2 routers, I have configured a trunk in the switch chip for all vlans to be able to communicate over these routers. router1 has (vlan2, vlan3) configured on its trunk port with respective ip adresses (ip1_2, ip1_3) and router2 has (vlan2,vlan3) also configured on its trunk port with respective ip adresses (ip2_2, ip2_3). I have several computers plugged into router1 on vlan 2 and vlan3 receiving dhcp from router1 that are correctly using ISP1 and also communicating correctly intervlan through router1. . However, I would like one of these computers plugged in vlan2 of router1 to have the privilege to use ISP2 on router2 for better speeds. If I change the gateway on that computer from ip1_2 to ip2_2, It can connect to the internet through ISP2 with good speed but If I want to communicate with a computer back on vlan3 plugged in router1 (eg remote desktop) then it can also connect but the connection becomes very slow (it takes about 10 seconds to get a remote desktop session running whereas it took 2secs before). So after setting router2 as gateway, it does find its way back to router 1 so I think all my routes are correct but somehow it does so very sluggishly.Can anyone help me find what I am missing...

It may not be routing, but perhaps server looking up client's address in DNS, or something like that (although it would be strange, when both are still in same IP subnet). I'd fire up packet sniffer on both client and server and see what exactly happens, where the delay comes from.

The 2 computers are on different subnets as they are on different vlans (192.168.1.0/24 and 192.168.2.0/24) but I have default routes pointing these adress spaces to their vlans in each router. So if I remote from 192.168.2.1 to 192.168.1.1, should it be using DNS at all? Also it seems it doesn't connect correctly through ISP2 after all. I can get a good speed test readin and i was able to login to this forum but when I repeatedly tried to post, the server could not communicate back to me and publish my post. I have qos being done on ether1 on both routers but no qos on internal forwarding. I also have nat on each eher 1 for each ISP. Should there be another nat for internal forwarding? I have never used the packet sniffer but will give it a try.

Servers often look up hostname of clients. Private addresses usually don't have it in DNS, but it might also come from other sources, e.g. some local-subnet resolution. Depending on how much server tries to find it, it might cause delays. I can't say that it must be this, but it's the kind of problem that can happen.

You shouldn't need any NAT for different internal networks.