Discussion

Table 7-1. Some interface media names
Interface type Identifier Name
Network at
fe
ge
se
so
t1
ATM over SONET/SDH
Fast Ethernet
Gigabit Ethernet
Serial
SONET/SDH
T1
Services
Special
The location portion of the interface name identifies which slot the FPC is in, which
PIC slot on the FPC the media is installed on, and the specific port on the PIC. Most
M-series and T-series routers have either four or eight FPC slots, and each slot has
either two or four PIC locations. On J-series routers, there can be up to six FPC slots.
To illustrate interface naming, the interface name for the first port of a Fast Ethernet
PIC installed on the FPC in slot 2, in the first PIC position, would be:
fe-2/0/0
For channelized interfaces, such as T1, the interface name includes the channel number.
The name for the first channel on a T1 interface would be:
t1-1/1/0:0
es
gr
mo
mt
sp
lo0
fxp0
fxp1
Encryption Services
Generic Route Encapsulation tunnel interface
Monitoring Services
Multicast tunnel interface
Services (for ES and AS PICs)
Loopback
Out-of-band management
Internal management
When numbering the slots, ports, and channels in an interface name, the first item is
0, not 1. For routers that have eight FPC slots, the slots are numbered from 0
through 7. Most PICs have four locations, numbered 0 through 3, and port and
channel numbering starts at 0. You can find the FPC and PIC slot numbers on the
router chassis, and the port numbers on the PIC faceplate.
JUNOS interfaces consist of a number of layers that affect how you configure them.
Like an onion with an outer skin and inner layers, the outer skin of the interface is
the physical interface, which generally encompasses the entire physical device. On
the physical interface, you set properties that control the behavior of the device itself.
These properties typically correspond to OSI Reference Model Layer 1 and Layer 2
properties. As examples, Ethernet physical interface properties include the speed (10
Mbps or 100 Mbps) and half-duplex or full-duplex operation; T1 interface properties
include framing, encoding, loopback, and setting up a Bit Error Rate Test
(BERT); and for SONET, Automatic Protection Switching (APS) is a physical property.
You configure the physical properties of an interface in two places: directly
192 | Chapter 7: Router Interfaces
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