Network Interface and Link Types

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 The product is obsolete with no plans for support.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.

Network Interface and Link Types

Technical documentation

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Number of Network Interfaces

Priority of Network Interfaces