Broadcast Addresses; Routing Services - Bay Networks 5390 Administering

Network Protocols
For example, a local network that uses the network address of 129.91 creates two subnets. All hosts
assigned to one subnet use the Internet address 129.91.1.x, where x is the host address; hosts assigned
to the other subnet use 129.91.2.x. In this local network, each host has a subnet mask defined as
255.255.255.0. This mask indicates that the first and second octets are the network addresses, the
third octet is the subnet address, and the fourth octet is the host address.
The Model 5390 server also supports supernetting for Class C addresses. Supernetting allows you
to use a subnet mask that is smaller than the default subnet mask derived from the Internet address'
class. The minimum supernetted subnet mask for a Class C address is 255.255.0.0 and the maximum
is 255.255.255.252 (excluding 255.255.255.128, which is illegal).
For subnet addressing to work in any local network, all hosts on the network must have the same
subnet mask defined. Hosts can be informed of the subnet mask in one of three ways: 1) defined in
the configuration, 2) obtained from the host's Internet address, and 3) sending out an ICMP Address
Mask Request and receiving a reply from an authoritative agent.
The Model 5390 server can be configured as an authoritative agent on the network and reply to
ICMP Address Mask Requests.

Broadcast Addresses

The Model 5390 server can configure the broadcast address. The standard broadcast address uses
a host address of all ones; for example, 129.91.0.255 (assuming a subnet mask defined as
255.255.255.0). This style is used with 4.3BSD hosts. The 4.2BSD networks use a broadcast address
of zeros for the host address; for example, 129.91.0.0. The Model 5390 broadcast address can be
configured for either type of network requirement.

Routing Services

In a simple network of a single LAN cable in which all hosts are attached, routing is not a
requirement. However, a simple local network can grow to multiple networks connected by routers
or gateways. At this point, routing services become a necessity to reach hosts located on distant
networks. Routing services inform hosts on one network of the route to a host on the other network.
The Model 5390 server can use static (or fixed) route entries and can "listen" for and transmit
dynamic routing updates. The dynamic routing updates involve the Model 5390 server using a
C5-6
NOTE: Entering a subnet mask of 255.255.255.255 indicates that the
Model 5390 server does not have an Ethernet connection.
893-741-B