I have following setup:
CRS326 --- CCR1009 --- RB2011 --- internet
CCR1009 is bridging one network that spans between CRS326 and RB2011 (which is wifi network). RB2011 is router in this network there's DNS server connected to it. CCR doesn't have an IP address in this network. It just performs bridging.
There's NAT for DNS servers so that no matter what DNS server user specifies, it's always redirected to DNS server connected to RB2011. I like to have possibly synchronized configs so I have 1:1 the same NAT rules on CCR and RB, regardless fact that CCR does not actively participate in this network routing.
When I'm performing NAT in this bridge on CCR it doesn't forward packets (on bridge level). I have bridge firewall enabled. Here's what exactly happens if NAT on CCR is enabled:
1. CCR gets packet from 192.168.4.6 to 188.8.131.52
2. CCR changes dst IP to 192.168.10.9
3. CCR doesn't forward packet any further. The same happens if I perform NAT to 192.168.4.6.
If I disable NAT on CCR bridge it does forward packets. My question is - why doing NAT breaks forwarding if router doesn't have addressing on bridge. I somewhat understand it because changing destination IP can potentially turn bridging into routing and considering router has no IP in this bridge it can't perform routing but does NAT always turn bridging into routing? Is there any way to fix it (other than disabling NAT) like for example specifying 192.168.0.0/24 address for bridge (so that it's not functional IP address just indication of network on bridge or something similar)?