@KJK as a result of consideration, it needs to access 10.168.0.0 → 10.168.100.0. because there is printer in 10.168.0.0 only. PC2 have to use printer. Oh god. Please save me.

@KJK thank you for reply That routing table is on ER605. and PC1 and PC2 are windows PC. I wish set 0.0.0.0 subunet. it was error but then I set 0.0.0.0. Do you know solution for it? I will consider...

@d0ugmac1 >It will NOT allow Internet->PC access →yes! That's exactly right. I can search on google but I can't browse web site. modem on your network diagram is other company router on my network...

@d0ugmac1 Thank you for your kind reply and sorry my english is bad What does mean 'depletion' is No IP address assigned by DHCP server in 10.192.168.0.0 network. There are many PCs other than PC1 in...

@d0ugmac1 As a result of my careful consideration it is unrealizable it set DMZ IP for PC2 I find PC2 IP doesn't change for other system. why wanna install ER605 this network is IP for DHCP is　...

@d0ugmac1 Thanks for reply.I will try your advice.