This describes how dial on demand works within the Netopia Router.
The Netopia Router implements a powerful feature called dial on demand (DOD) routing. DOD allows the Netopia Router to automatically bring up a connection to an Internet Service Provider (ISP) or other provider on demand without having the User's Reference Guidely establish a connection. This Technical Note explains how DOD routing works within the Netopia Router and how to set it up to work efficiently.
Below is a list of hardware and firmware loads that this Technical Note is based upon:
| Hardware | Firmware/Version | Installed Options |
| Any Netopia Router | 3.1.3 or later | None |
This is the configuration of the hardware that is referenced in this Technical Note:
There are several elements in the Netopia Router that work together to perform the function of DOD routing. These are the Connection Profiles, Remote IP Address, Remote Subnet Mask, Default Gateway, Ethernet IP Address, Ethernet Subnet Mask, and IP Routing Table. Each of these components are described below.
- Connection Profile. The Connection Profile contains attributes of the site that is being called. These attributes include things like the telephone number to dial, authentication, and the Remote IP Address and Remote Subnet Mask. For example, in the Network Diagram above Netopia A would have a Connection Profile for Netopia B as well as Netopia C.
- Remote IP Address and Remote Subnet Mask. These are the IP address and Subnet Mask of the router that is being called. The settings are located in the Connection Profile. In the Network Diagram above, if Netopia A had a Connection Profile for Netopia B, the Remote IP Address and Remote Subnet Mask would be 192.168.2.1 and 255.255.255.0, whereas a Connection Profile for Netopia C would have a Remote IP Address of 192.168.3.1 and a Remote Subnet Mask of 255.255.255.0.
- Default Gateway. The Default Gateway is used by the Netopia Router to determine where to send IP packets not destined for its local network if it does not have an appropriate route in its IP Routing Table. The Default Gateway should match the Remote IP Address within at least one of the Connection Profiles unless the gateway is a router on the Netopia Router's local Ethernet network.
- Ethernet IP Address and Ethernet Subnet Mask. These are the IP address and Subnet Mask of the Netopia Router's Ethernet port on its local network. The IP address should be within the range of addresses provided by the ISP or other provider and the Subnet Mask defines how many addresses will be available to the local network.
- IP Routing Table. The IP Routing Table is the most important aspect for DOD routing and brings all the items described above together. On booting, the Netopia Router builds its routing table by looking at the Ethernet IP Address, Subnet Mask, Default Gateway, Remote IP Address and Remote Subnet Mask information. From these, the Netopia Router can determine when and how to bring up a connection and route packets across its WAN (ISDN) or Ethernet interface.
Here's a basic example of setting up DOD and the interaction of the Connection Profiles, Remote IP Address, Remote Subnet Mask, Default Gateway, Ethernet IP Address, Ethernet Subnet Mask, and IP Routing Table. This will describe Netopia C on Customer Site C dialing Netopia A on Customer Site A.
The Remote IP Address and Remote Subnet Mask in the Connection Profile on Netopia C for Netopia A look like the following:
Path: Main - Advanced - WAN Setup - Connection Profiles - Display/Change Connection Profile - [Netopia A Profile name] - IP Profile Parameters
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| IP Profile Parameters | |
| Remote IP Address: | 192.168.1.2 |
| Remote IP Mask | 255.255.255.0 |
| Filter Set... | |
| Remove Filter Set | |
| Receive RIP: | No |
| Transmit RIP: | No |
Configure IP requirements for a remote network connection here.
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The Ethernet IP Address, Ethernet Subnet Mask, and Default Gateway for Netopia C looks like the following:
Path: Main - Advanced - Network Protocols Setup - IP Setup
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| IP Setup | |
| Ethernet IP Address: | 192.168.3.1 |
| Ethernet Subnet Mask: | 255.255.255.0 |
| Default IP Gateway: | 192.168.1.2 |
| DNS Server: | 0.0.0.0 |
| Secondary DNS Server: | 0.0.0.0 |
| Domain Name: | |
| Receive RIP: | Off |
| Transmit RIP: | Off |
| Static Routes... | |
Set up the basic IP attributes of your Netopia in this screen.
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On booting, Netopia C builds its routing table by looking at the Ethernet IP Address, Subnet Mask, Default Gateway, Remote IP Address, and Remote Subnet Mask information. The IP Routing Table for Netopia C then looks like the following:
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| IP Routing Table | |||||
| Network Address | Subnet Mask | via Router | Port | Age | Type |
| ------------------------SCROLL UP---------------------- | |||||
| 0.0.0.0 | 0.0.0.0 | 192.168.1.2 | WAN | 309 | Management |
| 192.168.1.0 | 255.255.255.0 | 192.168.1.2 | WAN | 309 | Local |
| 127.0.0.1 | 255.255.255.255 | 127.0.0.1 | lp1 | 309 | Local |
| 192.168.3.0 | 255.255.255.0 | 192.168.3.1 | EN1 | 309 | Local |
| -----------------------SCROLL DOWN--------------------- | |||||
| UPDATE | |||||
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After booting there are four lines in the IP Routing Table. The first line is the Default Route which tells Netopia C that any IP traffic (0.0.0.0) for any network (0.0.0.0) that is not defined by a route from a Connection Profile will be sent to the router at the IP address 192.168.1.2.
The next line tells Netopia C how to get to network 192.168.1.0 with a Subnet Mask of 255.255.255.0 via the router at 192.168.1.2. The last octet in the network address is zero, which is derived from the Subnet Mask for a Class C network of 254 hosts. In an IP network, the subnet is defined by an all zeros address (network address) and an all ones address (broadcast). This line is generated from the Remote IP Address and Remote Subnet Mask in the Connection Profile for Netopia A.
The next line is a loopback address (127.0.0.1), which is used for certain applications not discussed here. This line will always be present in the IP Routing Table.
The last line tells Netopia C how to get to network 192.168.3.0 with a Subnet Mask of 255.255.255.0 via router 192.168.3.1. This is the route for Netopia C's local Ethernet network and is derived from the Ethernet IP Address and Ethernet Subnet Mask.
In summary, for Netopia C's IP Routing Table, you can see the following layout:
- Default gateway
- Connection profile for Netopia A (Remote IP Address, Remote Subnet Mask)
- Loopback address
- Local IP network (Ethernet IP Address, Ethernet Subnet Mask)
Now look at how DOD works. If a workstation configured properly for Netopia C's network and cabled directly to Netopia C generates an IP packet destined for a host on Customer Site A's network, Netopia C receives the packet and looks at the destination IP address. Let's say that IP packet is destined for 192.168.1.1. Netopia C then looks in its IP Routing Table to determine the best route for the IP packet. Netopia C will find the following route:
| 192.168.1.0 | 255.255.255.0 | 192.168.1.2 | WAN | 309 | Local |
Since the destination IP address (192.168.1.1) falls within this route, Netopia C will use this route to deliver the IP packet. This route is associated with a Connection Profile so Netopia C will use the information contained within the Connection Profile to make a DOD connection over ISDN, in this case to Netopia A. Once the connection is established, the IP packet is delivered to its destination.
If the workstation cabled to Netopia C generates an IP packet destined for an unknown network, Netopia C will again receive the packet and look at the destination IP address. Let's say that IP packet is destined for 163.176.4.32. If the destination IP address does not match any routes in its routing table, Netopia C will send the IP packet to its Default Gateway. The Default Gateway in Netopia C's routing table looks like the following:
| 0.0.0.0 | 0.0.0.0 | 192.168.1.2 | WAN | 309 | Management |
The Default Gateway points to a router at 192.168.1.2 which in turn is associated with the Connection Profile for Netopia A. Similar to the situation above, Netopia C will use the information contained within the Connection Profile to make a connection over ISDN, in this case to Netopia A. Once the connection is established, the IP packet is delivered to the remote router, and then to its destination.
Now look at a more complex routing table. This is the routing table for Netopia A, which has a Connection Profile to dial Netopia C and Netopia B on demand and also has an IP address, Subnet Mask, and default gateway on its local IP network.
The Remote IP Address and Remote Subnet Mask in the Connection Profile on Netopia A for Netopia B looks like the following:
Path: Main - Advanced - WAN Setup - Connection Profiles - Display/Change Connection Profile - [Netopia B Profile name] - IP Profile Parameters
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| IP Profile Parameters | ||
| Remote IP Address: | 192.168.2.1 | |
| Remote IP Mask | 255.255.255.0 | |
| Filter Set... | ||
| Remove Filter Set | ||
| Receive RIP: | No | |
| Transmit RIP: | No | |
Configure IP requirements for a remote network connection here.
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The Remote IP Address and Remote Subnet Mask in the Connection Profile on Netopia A for Netopia C looks like the following:
Path: Main - Advanced - WAN Setup - Connection Profiles - Display/Change Connection Profile - [Netopia C Profile name] - IP Profile Parameters
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| IP Profile Parameters | ||
| Remote IP Address: | 192.168.3.1 | |
| Remote IP Mask | 255.255.255.0 | |
| Filter Set... | ||
| Remove Filter Set | ||
| Receive RIP: | No | |
| Transmit RIP: | No | |
Configure IP requirements for a remote network connection here.
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The Ethernet IP Address, Ethernet Subnet Mask, and Default Gateway for Netopia A looks like the following:
Path: Main - Advanced - Network Protocols Setup - IP Setup
**************************************************************
| IP Setup | ||
| Ethernet IP Address: | 192.168.1.2 | |
| Ethernet Subnet Mask: | 255.255.255.0 | |
| Default IP Gateway: | 192.168.1.1 | |
| DNS Server: | 0.0.0.0 | |
| Secondary DNS Server: | 0.0.0.0 | |
| Domain Name: | ||
| Receive RIP: | Off | |
| Transmit RIP: | Off | |
| Static Routes... | ||
Set up the basic IP attributes of your Netopia in this screen.
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On booting, Netopia A builds its routing table by looking at the Ethernet IP Address, Subnet Mask, Default Gateway, Remote IP Address, and Remote Subnet Mask information. The IP Routing Table then looks like the following:
**************************************************************
| IP Routing Table | |||||
| Network Address | Subnet Mask | via Router | Port | Age | Type |
| ------------------------SCROLL UP---------------------- | |||||
| 0.0.0.0 | 0.0.0.0 | 192.168.1.1 | EN1 | 64 | Management |
| 192.168.1.0 | 255.255.255.0 | 192.168.1.2 | EN1 | 64 | Local |
| 127.0.0.1 | 255.255.255.255 | 127.0.0.1 | lp1 | 64 | Local |
| 192.168.2.0 | 255.255.255.0 | 192.168.2.1 | WAN | 64 | Local |
| 192.168.3.0 | 255.255.255.0 | 192.168.3.1 | WAN | 64 | Local |
| -----------------------SCROLL DOWN--------------------- | |||||
| UPDATE | |||||
**************************************************************
After booting there are five lines in the IP Routing Table. The first line tells Netopia A that any IP traffic (0.0.0.0) for any network (0.0.0.0) that is not defined by a route from a Connection Profile will be sent to the router at the IP address 192.168.1.1. This is Netopia C's default route and is located on Netopia A's local Ethernet network.
The next line tells Netopia A to get to network 192.168.1.0 with a Subnet Mask of 255.255.255.0 via the router at 192.168.1.2. The last octet in the network address is zero, which is derived from the Subnet Mask for a Class C network of 254 hosts. In an IP network, the subnet is defined by an all zeros address (network address) and an all ones address (broadcast). This is the route for Netopia B's local Ethernet network and is derived from the Ethernet IP Address and Ethernet Subnet Mask.
The next line is a loopback address (127.0.0.1), which is used for certain applications not discussed here.
The next line tells Netopia A to get to network 192.168.2.0 with a Subnet Mask of 255.255.255.0 via the router at 192.168.2.1. This line is generated from the Remote IP Address and Remote Subnet Mask in the Connection Profile for Netopia B.
And the last line tells Netopia A to get to network 192.168.3.0 with a Subnet Mask of 255.255.255.0 via router 192.168.3.1. This line is generated from the Remote IP Address and Remote Subnet Mask in the Connection Profile for Netopia C.
In summary, for Netopia A's IP Routing Table, we can see the following layout:
- Default gateway
- Local IP network (Ethernet IP Address, Ethernet Subnet Mask)
- Loopback address
- Connection profile for Netopia B (Remote IP Address, Remote Subnet Mask)
- Connection profile for Netopia C (Remote IP Address, Remote Subnet Mask)
Now see how DOD works with multiple routes. If a workstation configured properly for Netopia A's network is cabled directly to Netopia A and generates an IP packet destined for a host on Customer Site B's network, Netopia A receives the packet and looks at the destination IP address. Let's say that IP packet is destined for 192.168.2.1. Netopia A then looks in its IP Routing Table to determine the best route for the IP packet. Netopia A will find the following route:
| 192.168.2.0 | 255.255.255.0 | 192.168.2.1 | WAN | 64 | Local |
Since the destination IP address (192.168.2.1) falls within this route, Netopia A will use this route to deliver the IP packet. This route is associated with a Connection Profile so Netopia A will use the information contained within the Connection Profile to make a connection over ISDN, in this case to Netopia B. Once the connection is established, the IP packet is delivered to its destination.
Now let's say the workstation cabled directly to Netopia A generates an IP packet destined for a host on Customer Site C's network. Netopia A receives the packet and looks at the destination IP address. Let's say that IP packet is destined for 192.168.3.1. Netopia A then looks in its IP Routing Table to determine the best route for the IP packet. Netopia A will find the following route:
| 192.168.3.0 | 255.255.255.0 | 192.168.3.1 | WAN | 64 | Local |
Since the destination IP address (192.168.3.1) falls within this route, Netopia A will use this route to deliver the IP packet. This route is associated with a Connection Profile so Netopia A will use the information contained within the Connection Profile to make a connection over ISDN, in this case to Netopia C. Once the connection is established, the IP packet is delivered to its destination.
If the workstation cabled to Netopia C generates an IP packet destined for an unknown network, Netopia C will again receive the packet and look at the destination IP address. Let's say the network is 163.176.4.32. If the destination IP address does not match any routes in its routing table, Netopia A will send the IP packet to its Default Gateway. The Default Gateway in Netopia A's routing table looks like the following:
| 0.0.0.0 | 0.0.0.0 | 192.168.1.1 | EN1 | 64 | Management |
The Default Gateway points to the router at 192.168.1.1 which in turn is located on Netopia A's local Ethernet network. Netopia A will then send the IP packet with an unknown destination out its Ethernet port to Router A at the IP address of 192.168.1.1. Router A will then look in its IP routing table to determine the best method to deliver the IP packet.
Now there are some things to watch out for when configuring Connection Profiles and IP address information. One would be if the default gateway in the Netopia Router is not an IP address located within the local or remote subnets, the Default Gateway will be disabled and the following event will be logged in the Device Event History:
| 22:04:43 | 11/18/96 | * | IP: | Route 0.0.0.0/0.0.0.0 | not installed |
This is because the Default Gateway's address is outside any known routes in the IP routing table and therefore cannot function, so the Default Gateway is disabled.
Another problem would be the fact that Connection Profiles should not have overlapping IP information. Since the Remote IP Address and Remote Subnet Mask are entered directly into the IP Routing Table, if two Connection Profiles share the same Remote IP Address and Remote Subnet Mask, the profiles will conflict. On booting, when the Netopia Router builds its IP Routing Table, the conflicting profile will be disabled and an event will be logged in the Device Event History.
Dial On Demand is a powerful feature of the Netopia Router and when configured and used properly, can be an effective tool for routing IP traffic automatically. Please note that the network information and TCP/IP addresses given in this Technical Note are for example purposes only and should not be used when connecting to the Internet.