I have my printer on 10.0.10.20 ip on vlan 1. The guest network is configured on 192.168.1.0/24 on vlan2.
I have a rule in the zyxel firewall to allow traffic from vlan2 to vlan1:s printer.
Windows will not detect the printer by automatic but I can easily type the address (10.0.10.20) and the printer will be added and everything will work.
However on ios devices with airprint I cannot find any way to add the printer manually it seems to only search in the current ip-network.
I do not have a domain.
Any ideas how I can use airprint when the printer is on another network-ip / vlan?
What devices are you talking about? Router? Wireless AP? Other?
What you experiencing is typical broadcast issue, MS Networking and Bonjour will not broadcast on multiple networks unless there is some kind of repeater/proxy that will re-broadcast the advertisements to the 2nd network.
My Cisco SG-200-26 layer 2 switch appears to have a mode allowing Bonjour messages to flood all vlans, but I'm not sure that would help unless the printer and the ios device both used Bonjour for discovery.
In any case, it seems that the simple solution would be to find a menu or other path to inform the ios device what the printer ip is. Visiting an ios hacking forum may be necessary to find the appropriate knowledge base.