On my first ISP I have several public IPs with srcnat and dstnat in place to map them to customers on the internal network.

1.1.1.1 dstnat to 192.168.1.11 (Cust A)
1.1.1.2 dstnat to 192.168.1.12 (Cust B)
1.1.1.3 dstnat to 192.168.1.13 (Cust C)
...and so on.

But now I am routing them through a new ISP with a new set of IPs, and I am getting some difficult issues, which is making me wonder if I am routing properly. Customer A has an IP Phone that is no longer able to connect to their phone server, and after much troubleshooting, I have determined it is because they arent the first IP on the set of addresses I have assigned to the WAN interface of my router. Heres an example:

5.5.5.1 dstnat to 192.168.1.12 (Cust B)
5.5.5.2 dstnat to 192.168.1.11 (Cust A)
5.5.5.3 dstnat to 192.168.1.13 (Cust C)
...and so on.

I noticed that if I move Cust A to the first IP on the list, it starts working, but anywhere else, it doesnt. I hope I'm just missing something simple, thanks for your time.

Hi,

just defining DST-NAT rules isn't the whole thing, because it only handles incoming traffic.
You need to define corresponding SRC-NAT rules aswell.

Regards,
Ape

Read this: viewtopic.php?f=2&t=126724&p=623599#p623599 post and quoted thread in it.

Thanks for your replies, although I am doing both a SRCNAT and DSTNAT rule for each external IP I am pushing through to an Internal IP. It seems to only work properly for the first IP listed in the list of IPs assigned to the WAN interface of the Mikrotik.