I’m doing work for a client remotely. They are physically very, very far away from me - if anything goes very wrong I have to take an airplane and then drive for 4 hours to get there 
. I ask anyone here if they can review my plan and tell me if I’m missing anything or warn me if I’m going to run in to any trouble. I’d really appreciate it.
Everything is connected to a RB1100 running v5.6
Connected to ether1 is ISP #1 with one chunk of IP addresses. We can not do BGP with ISP #1.
The goal for the ISP #1 connection is to make it a backup for ISP #2, we do not even want traffic going to ISP #1’s IPs coming in that one, so I have renumbered everything else and am down to the servers now.
ether10 is the new ISP and has it’s different IP addresses. ISP #2 uses Vlan15. They are connected to ether10, and I set up vlan15-e10 with an IP address on that subnet. I can ping it from the outside, that it working. Traffic is being NATted out it successfully.
ether13 has an unmanaged 24 port switch plugged in to it. There are some servers on that switch, each configured with an IP from ISP #1. ether13 has an IP address from that subnet, it is the default gateway for all of the servers.
My plan is to create a bridge (with Use IP Firewall & Use IP Firewall For Vlan), add ports ether13 and vlan15-e10 to it. Hopefully, I can have no IP at all on ether13 (as always, low on IPs), have the servers use the IP of vlan15-e10 as their default gateway, and just have to renumber the servers to IPs in that subnet.
I’m all for setting a secondary IP on each server, trying to minimize downtime, but with two different ISPs, one Vlan one not, one the gateway one not, it may just be easier to renumber one at a time and hope for the best.
Various notes: These are Linux servers, and I can rebuild the kernels with Vlan support, install Vlan-tools, etc. but I’m hoping to avoid that. I can get in through both ISPs, so I’m hoping to not kick myself out during this process. The servers include dns, mx/smtp, pop3/imap, www so I will be having a heart-attack until it is finished.
I’d sure love to hear a thumbs up or a thumbs down before I actually do it All comments welcome and appreciated.