Viper SC+™ IP Router for Licensed Spectrum PN 001-5008-000 Rev. C | Page 142.2. IP FORWARDING MODESAll Ethernet capable devices, or hosts, have at least one IP address and a subnet mask assigned to it. The IP addressidentifies a specific device and the subnet mask tells the device which other IP addresses it can directly communicatewith. When any host needs to communicate with another device that is not within the same local area network it willfirst send the data packet to the gateway or router. The gateway or router will forward the packet to the desiredlocation. Often times a packet will pass through several gateways or routers to get to its final destination.The Viper SC+ has two different modes of operation: Bridge Mode – Bridge mode is for quick setup of units all on the same network. Router Mode — Router mode is for advanced networks.Both of these modes are explained in the sections that follow.2.2.1. BRIDGE MODEBridge mode is the simplest configuration for all Viper networks. Viper may be configured for bridge mode only whenall devices are located on the same Local Area Network (LAN). Thus, all units in the network can communicate directlywith all other units in the network.Each Viper has only one IP address assigned to it and the subnet mask is the same for every Viper in the network.Bridge communications does not require each Viper to have a unique IP address, but it is highly recommended andnecessary for remote programming of the radio.Every Viper ships from the factory with the default Ethernet IP address of 192.168.205.1 and a subnet mask of255.255.255.0. The default subnet of the Viper consists of addresses from 192.168.205.0 to 192.168.205.255. The firstand last IP address of each subnet is reserved, no matter what the subnet size is. The first IP address in the subnet isthe Network ID. The last IP address in the subnet is the Broadcast Address.Bridge Mode Example 1This example illustrates a sample Viper network. The subnet consists of IP addresses ranging from 192.168.205.0 to192.168.205.255. The subnet mask is 255.255.255.0. This subnet is sometimes indicated as 192.168.205.1/24 since thesubnet mask 255.255.255.0 contains 24 ones (followed by 8 zeros) when converted to binary. The first address 192.168.205.0 is reserved for the Network ID. The last address 192.168.205.255 is reserved for the broadcast address. There are 254 valid IP addresses that may be assigned to hosts on the network.Ethernet Subnet Mask 255.255.255.0Network ID 192.168.205.0Broadcast Address 192.168.205.255Viper #1 192.168.205.1/24PLC/RTU #1 192.168.205.10/24Computer #1 192.168.205.100/24Viper #2 192.168.205.2/24PLC/RTU #2 192.168.205.20/24Viper #3 192.168.205.3/24PLC/RTU #3 192.168.205.30/24Viper #4 192.168.205.4/24PLC/RTU #4 192.168.205.40/24… Viper #100: 192.168.205.253/24PLC/RTU #100: 192.168.205.254/24
