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I have two ISPs, ISP A 10.10.10.1/30 connect to mikrotik router with local IP 172.17.17.0/24, and ISP B 20.20.20.1/30 connect to cisco router with local IP 192.168.100.0/24. recently I bought new mikrotik router, I want to load ballance this two ISPs with ecmp technique. I have read tutorials, but it's said two ISPs go straight in into a router, but my case each ISP going through a router first.

My question:

Can I implement load ballance ecmp on this situation? Can give me step by step how to achieve this?

Here is my current topology.

topology current condition

Uwe Keim
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casthrotopes
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  • Do you deal with any incoming traffic at all? Implementing this should be doable, but it would create double-NATing through the first set of routers, and then through the second router (r3 in your topology). Having services hosted on the inside, is a bit more hassle when dealing with the double-NATed connections. – xstnc Jan 07 '21 at 09:38
  • Balancing can be done by using the providers facing router. The other 2 don't matter. – Overmind Jan 07 '21 at 09:46
  • Is ISP A providing a RFC1918 private net behind a NAT, or did you make the IP address up? Please edit to replace obfuscated public addresses with your real addresses, or at least reserved addresses not in use. Such as the documentation blocks `192.0.2.0/24` `198.51.100.0/24` or `203.0.113.0/24` – John Mahowald Jan 07 '21 at 17:06
  • @xstnc yes ofcourse i make double NAT, i pick an ip address from local ip of each router and add into r3 router and use r1 and r2 gateway into r3 router, then i make nat with out interface using port that connect to r1 and r2 then i make it masquerade. it work and can use internet, but still separated network. i want load all of them in R3, how to deal with this ? – casthrotopes Jan 08 '21 at 02:19
  • @Overmind so i must bypass r1 and r2 router and straight connect to r3 router from isp's line ? – casthrotopes Jan 08 '21 at 02:20
  • If R3 can use dual WAN you don't need anything special on the other 2, just to connect them to the main one. All the routing and load balancing config will be on R3. – Overmind Jan 08 '21 at 07:19
  • @casthrotopes - Can you clarify "still separated network"? Even if both WAN ports on R3 got the public IPs directly, it would still be separate networks. What is on the LAN side of R3 is everything "internal", and anything on the WAN end is "external". Using either public IPs or the R1 and R2s local LAN side addresses does not change that fact. The only thing you would work around by having the public addresses directly on R3 is the double NAT. – xstnc Jan 09 '21 at 03:17
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    @xstnc yes it works, i just configure everything in R3 and yes indeed there is nothing to do with the other routers, problem solve thanks. Now it can load ballance with failover system. – casthrotopes Jan 12 '21 at 02:23

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