Hi guys I am having a problem with my debian server or my vpn router I am not sure which one is causing the problem at hand. Basically I have a debian server running which has 2 interfaces, one interface that is connected to the public network with one IP, then a second interface which is connected to the lan. I have different serices listening on each interface, I do not have a firewall/iptables running on this box. It is open all the way around.

Public Interface: ftp, sftp, ssh: example: 64.0.64.5
Internal Interface: sendmail, samba, hylafax, httpd: 192.168.100.237

I then have a cisco router, which is running easy vpn server and handling all routing within my network.

External Interface: example: 64.0.64.6
Internal Interface: 192.168.100.1
VPN DHCP pool: 172.26.16.100-200

I have multiple windows servers within this network setup the same way,with a public interface and an internal interface. When I login over the vpn I can connect to SDM (The router GUI/Gateway GUI) I can connect to any windows server or desktop, or printer, in the network.

The problem is that, I cannot connect, see, ping, or scan the linux box. All of my machines in the network are on the 192.168.100.0 network, windows or linux. I can connect to the vpn, the vpn client receives a 172 address and the cisco router handles the routing between the vpn VLAN and the internal network VLAN I can connect to all windows servers.
I can ping and see the linux box from the windows servers and desktops but I cannot connect to the linux box directly when connected to the vpn.

If this is confusing I will try to reword it but long story short my vpn works fine my windows servers work fine my linux box works fine, but I can't get to it from the 172 network and I don't know why because the cisco router should be handling the router.

Any help is appreciated.

I suppose because all packets goes to VPN
Check the routing.