I have the following port forwarding setup working:

cablemodem <-> DVG-1120M <-> Linux firewall/mail/webserver <-> LAN

Inside address range (DVG): 192.168.15.0/24

DVG-1120M IP address (LAN side): 192.168.15.1
Linux box addresses: 192.168.15.9 (DVG side); 192.168.22.254 (LAN side)

LAN address range: 192.168.22.0/24

Ports forwarded in DVG:

Port 22 TCP -> 192.168.15.9 SSH
Port 25 TCP -> 192.168.15.9 SMTP (mail)
Port 80 TCP -> 192.168.15.9 HTTP

For FTP you'd need to forward both 20 TCP and 21 TCP unless the ftp will be passive (PASV) mode, in which case just 21 TCP will suffice.

These serve my needs and give me the QoS feature of the DVG.

Now there's no reason why another router shouldn't work in place of the Linux box I'm using as a router, with those same ports forwarded to a server behind it, or maybe with that server in the router's DMZ. In any case the ports are forwarded to the address of the next machine in the chain, which may not be the final destination, comprendez (as in double NAT with multiple Gateways in sequence) ?

Oh... for those having trouble with getting the DVG to keep the settings, always choose "Continue and 'Restart System' later" after each edit and when you are done editing, choose "Save & Restart System" from the system menu at the left and choose "Yes" when it asks if you want to save the settings. It always works for me!

Note: If using the telnet command line, the ACR (described below) can be programmed much nicer and more accurately.
1) you can use more than 30 entries
2) you can switch the default to pstn, so as to specify the only numbers PERMITTED in the list (BTW use "x" not "T" so as to also reject numbers too short or too long) to use voip (when leaving the PSTN jack not connected.
3) don't forget about permitting emmergency numbers !!!
4) the "remove digits" option is good for password-protecting LD calls

You acknowledge that performing a reset of the Equipment without permission from PRIMUS may cause Service malfunction and any damage to the Equipment caused by such malfunction will be the responsibility of the Customer. Where the Equipment is owned by PRIMUS, You will be responsible for charges for damage to the Equipment.

First, a clarification for those who may not be familiar with routers, gateways, etc. The Primus TBB gateway (also somtimes referred to as an ATA - Analogue Telephone Adaptor) is essentially a router with the added functions of a VoIP ATA.

With that in mind, also consider that all routers have processors in them that perform calculations necessary for the functions and features of the router (ex. Routing Packets, Firewall Rules, DMZs, etc.). Because of these features and functions, the router has to do calculations for each packet that passes through it.

Because of this, there is a limit as to the number of concurrent connections that a router can sustain. The actual number of connections is unique to that router's specific model. Some routers have better hardware than others, allowing them to sustain a high number of connections. Many "home or small office" or "Cable / DSL" routers are not nearly as powerful as large scale routers (that's why they don't cost as much, and trust me those high end routers are pricey). Generally, the old saying "You get what you pay for" seems very appropriate to this topic.

To normal internet users, this limit isn't an important factor. They will never likely come close to the limit of connections while doing normal surfing on the web, even if they share their internet with multiple computers.

For those of us who like to make the most of our high speed connections, this limit is very important. The reason for this is that file sharing systems work by establishing a large number of connections with other computers on the internet so that files can be shared. If not configured properly, your file sharing program could cause your router to crash over time.

It is considered common for most home use routers to support approximately 255 concurrent connections. It is also considered good practice to configure your file sharing program to use about 66% of the connections that your router can support. So, using a setting of around 160 connections should keep you safe. Of course, you can tweak it for maximum performance if you wish.

How do you do this? Well every file sharing program is different, so all I'm going to say is that you'll have to look for the setting on your own. Many popular file sharing clients have options for the number of connections per file, number of files that can be downloaded at a time and also the maximum number of connections (or hosts) that can be used at a time. The latter is the setting of interest to us in this situation.

There are other settings that can impact your router as well. For example, Shareaza allows you to throttle packets. Generally, the default that Shareaza provides seems to work well. However, if you still have problems with your router and you have appropriately limited the number of connections, try adjusting the packet throttle (turn it up). This may help.

Some of you may be asking "What does this have to do with VoIP? Well, as I mentioned above, the VoIP gateway is itself essentially a router with a built in ATA. Some people here have reported problems with their gateways crashing, QoS not working properly, etc. I feel that some of these problems may be the result of the router being hammered by file sharing clients. Therefore, adjusting the above mentioned settings will likely go a long way to improving the stability and performance of your VoIP system.

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by canoe
last modified: 2005-10-16 12:15:27