iptables. Access to the Internet

Question

linux

Forwarded a port to connect via RDP to a computer in LAN through an alternative channel with an external ip. Before that, the computer went to the Internet through the main channel, but after I changed the default gateway for it, it refuses to go out through the new channel.
Wrote on the gateway (eth0 looks at LAN)
-A INPUT -i eth0 -s 10.30.105.0/24 -j ACCEPT
-A FORWARD -i eth0 -s 10.30.105.0/24 -j ACCEPT
Doesn't help.
Can someone advise please.

*nat 
:PREROUTING ACCEPT [774:204338] 
:INPUT ACCEPT [219:51348] 
:OUTPUT ACCEPT [287:17326] 
:POSTROUTING ACCEPT [299:18090] 
-A PREROUTING -d XXX.XXX.XXX.94/32 -p tcp -m tcp --dport 3389 -j DNAT --to-destination 10.30.105.133:3389 
-A POSTROUTING -s 10.30.105.0/24 -o eth1 -p tcp -j SNAT --to-source XXX.XXX.XXX.94 
COMMIT 
# Completed on Sun Jan 26 10:31:53 2014 
# Generated by iptables-save v1.4.7 on Sun Jan 26 10:31:53 2014 
*filter 
:INPUT ACCEPT [1:313] 
:FORWARD ACCEPT [0:0] 
:OUTPUT ACCEPT [14:1884] 
-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT 
-A INPUT -p icmp -j ACCEPT 
-A INPUT -i lo -j ACCEPT 
-A INPUT -p tcp -m state --state NEW -m tcp --dport 22 -j ACCEPT 
-A INPUT -p tcp -m state --state NEW -m tcp --dport 1521 -j ACCEPT 
-A INPUT -i eth1 -p tcp -m tcp --dport 3389 -j ACCEPT 
-A FORWARD -i eth1 -p tcp -m tcp --dport 3389 -j ACCEPT 
-A FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT

Answer 1

Line -A POSTROUTING -s 10.30.105.0/24
-o eth1 -p tcp -j SNAT --to-source XXX.XXX.XXX.94
COMMIT
Nat TCP traffic only. Therefore, nothing is pinged and sites are not opened (DNS does not resolve addresses).
Try replacing it with:
-A POSTROUTING -o eth1 -j MASQUERADE

Answer 2

so what doesn't work? internet access or rdp?

Answer 3

Allow ICMP and UDP for DNS. It is also not entirely clear how you resolved the routing through these channels. It is advisable to show ip -4 a ls, ip -4 r ls table all and ip -4 ru ls if allowing additional protocols does not help.