Modem/router in bridge, telnet to modem on same subnet


I've got the following:

pc linux ( => router LEDE ( === bridged ====> modem ( === ADSL ===> internet

my modem has port 23 (telnet) open to allow admin login for some basic commands.

I'm a programmer however my networking is shameful. How can I, on the PC, telnet to the modem?

I had tried steps in this post: [SOLVED] How to access the modem (which is in bridge mode)?

ifconfig uci get network.wan.ifname:0 netmask
iptables -t nat -I POSTROUTING -o uci get network.wan.ifname -d -j MASQUERADE

but no joy.

the correct way is here :

if its all on the same netmask just telnet -o, i would set my lan to another dhcp range though say like                      
Modem ----------->Bridged mode------->Router---------------------->Lan/Switches/PC/Server
forward dhcp            acquire wan ip address                    range of hosts for dhcp server