[pr3ddi]

Hi forum users,

can anyone help with a broadcast problem, please ?

Win7 <---> [INTERNAL SUBNET,WRT54GL] <---> [FRITZBox,EXTERNAL SUBNET] <---> Steam Link Box

I have a win7 pc running the steam client in a subnet [INTERNAL]/24 (WRT54GL/DD-WRT v24-sp2 (08/07/10) std) and the steam link box in a subnet [EXTERNAL]/24 (FRITZ!Box 3270). The steam link uses the ports 27031 UDP, 27036 UDP/TCP, 27037 TCP for communication. Discovery happens by broadcast on 27036 UDP from the box: https://support.steampowered.com/kb_article.php?ref=3629-RIAV-1617#networkports

After a couple of port-forwarding attempts I have found out that broadcasts can not be forwarded to another subnet. So my next try was to follow the one-to-one NAT guide from the wiki: http://www.dd-wrt.com/wiki/index.php/One-to-one_NAT
I have exposed the win7 PC successfully to the [EXTERNAL] network, but I still dont get the broadcasts (tested with wireshark).

Here are the scripts I am using:
ifconfig vlan:1 [NEW_EXTERNAL_IP] netmask 255.255.255.0 broadcast [EXTERNAL_NET].255

iptables -t nat -I PREROUTING -i vlan1 -d [NEW_EXTERNAL_IP] -j DNAT --to [INTERNAL_IP]
iptables -t nat -I POSTROUTING -o vlan1 -s [INTERNAL_IP] -j SNAT --to [NEW_EXTERNAL_IP]
iptables -I FORWARD -i vlan1 -d [INTERNAL_IP] -p udp --dport 27031 -j ACCEPT
iptables -I FORWARD -i vlan1 -d [INTERNAL_IP] -p udp --dport 27036 -j ACCEPT
iptables -I FORWARD -i vlan1 -d [INTERNAL_IP] -p tcp --dport 27036 -j ACCEPT
iptables -I FORWARD -i vlan1 -d [INTERNAL_IP] -p tcp --dport 27037 -j ACCEPT

I have also tried the following without success:
#iptables -t nat -I PREROUTING -i vlan1 -d [EXTERNAL_NET].255 -j DNAT --to [INTERNAL_IP]
#iptables -t nat -I PREROUTING -i vlan1 -s FF:FF:FF:FF:FF:FF -j DNAT --to [INTERNAL_IP]

Any ideas on how to make the broadcast / discovery possible ?

Pr3ddi

[Per Yngve Berg]

https://en.wikipedia.org/wiki/Simple_Service_Discovery_Protocol