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The network interface (NI), the software that provides an interface between a
node and a network, specifies the type and maximum number of links that can be
configured for a node. Because a node's network interface determines what links
can be configured for the node, links are said to be configured underneath
network interfaces.
There are nine types of network interfaces (in addition to loopback):
LAN for IEEE 802.3 and Ethernet networks, 100VG-AnyLAN
networks, and 100Base-T networks.
Token Ring for IEEE 802.5 networks.
FDDI for fiber optic networks.
100VG-AnyLAN for 100VG-AnyLAN networks.
100Base-T for 100Base-T networks.
Point-to-Point for networks that use Point-to-Point
routing.
X.25 for X.25 networks.
NS over SNA is no longer offered as a product and has been
removed from the Corporate Price List. The product is obsolete with
no plans for support.
Gateway half for nodes that function as gateway
halves.
Number of Network Interfaces
A system can have up to 48 network interfaces (NI) configured. One of these
network interfaces must be loopback. For each network interface, the maximum
number of links you can configure and the kinds of links possible are
determined by the network interface type, as follows:
A LAN network interface can have only one link configured under
it; however, a single link can reach a large number of nodes.
ThickLAN cable supports up to 100 nodes per segment; ThinLAN cable
can be used for up to 30 nodes per segment; and each Ethertwist
3000/iX can be used for up to 50 nodes. Up to two LAN NIs can be
active at a time per system, 100BT allows a maximum distance of 100m
between 2 nodes.
A Token Ring interface can have only one link configured under it;
however, a single link can reach a large number of nodes. Token Ring
3000/iX Network Link can support up to 250 nodes per ring using
shielded twisted pair (STP) cabling at 4 or 16 Mbps and 50 nodes per
ring using unshielded twisted pair (UTP) cabling at 4 Mbps. Only
one Token Ring NI can be active at a time per system.
An FDDI interface can have only one link configured under it;
however, a single link can reach a large number of nodes. FDDI/iX
Network Link can support up to 1000 nodes. Up to four FDDI NIs can
be active at a time per system.
A Point-to-Point network interface can have up to 40 links
configured under it. Point-to-Point links may be dial links, in which
a modem attached to a node is used to transmit and receive data
carried across telephone wires, or leased lines, in which data is
sent over data-grade lines leased from a private carrier. Up to 11
Point-to-Point NI's can be active at a time (one NI must be loopback)
for a total of 12 NI's per system..
An X.25 network interface can have from one to 11 links configured,
depending on the number of configured X.25 network interfaces on the
node. (A single node can have up to 11 NIs and up to 11 X.25 links.)
Each link can be connected to as many as 1,024 remote nodes, with
communication allowed with as many as 256 nodes at the same time.
Up to 11 X.25 NI's can be active at a time (one NI must be
loopback) for a total of 12 NI's per system..
A gateway half network interface can have only one link configured
under it (the gateway half link). Links connecting two gateway halves
can be only NS Point-to-Point 3000/iX Network links. Only one
gateway half NI can be active at a time per system.
If more than one (non-loopback) network interface is configured on a node, the
network portions of the IP addresses configured for the interfaces should
differ to correspond to the multiple networks to which the node belongs.
Refer to "Software Configuration Maximums" at the end of this chapter for
information on configuration path maximums.
Priority of Network Interfaces
If it is possible to reach a destination through more than one active NI, the
network determines which NI to select according to the following priority:
Loopback |
100VG-AnyLAN |
100Base-T |
FDDI |
LAN |
Token Ring |
X.25 |
Gateway Half |
Point-to-Point (router) |
If more than one NI of a given type is active, (for example, two X.25 NIs) the
network will select the one that it finds first.
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