Help understanding ASYNC lines

Danielh22185 · July 2014

So at work I am trying to understand the behavior of Async lines.

As far a what I know this is a configured dialer type interface that might be hooked up with a modem that is running ISDN to provide dial in services to the equipment. What I beleive I understand is the reason I am seeing the interface down is because it is not in use. So if my beliefs are correct would that mean that when it is in use it will show the interface as up maybe?

I referenced a few docs about it from Cisco:

Cisco IOS Dial Technologies Configuration Guide, Release 12.2 - Overview of Dial Interfaces, Controllers, and Lines [Cisco IOS Software Releases 12.2 Mainline] - Cisco
Cisco IOS Dial Technologies Configuration Guide, Release 12.2 - Overview of Dial Interfaces, Controllers, and Lines [Cisco IOS Software Releases 12.2 Mainline] - Cisco
Cisco IOS Dial Technologies Configuration Guide, Release 12.2 - Configuring Asynchronous SLIP and PPP [Cisco IOS Software Releases 12.2 Mainline] - Cisco

I wasn't able to determine behavioral type examples but did get some good info.

Here is the config on the interface if anybody can further clarify:

Group-Async1 is down, line protocol is down   Hardware is Async Group Serial
  MTU 1500 bytes, BW 1000 Kbit/sec, DLY 100000 usec, 
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation SLIP, loopback not set
  Keepalive not set
  DTR is pulsed for 5 seconds on reset
  Last input never, output never, output hang never
  Last clearing of "show interface" counters 10w5d
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: weighted fair
  Output queue: 0/1000/64/0 (size/max total/threshold/drops) 
     Conversations  0/0/256 (active/max active/max total)
     Reserved Conversations 0/0 (allocated/max allocated)
     Available Bandwidth 750 kilobits/sec
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     0 packets input, 0 bytes, 0 no buffer
     Received 0 broadcasts (0 IP multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
     0 packets output, 0 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     0 unknown protocol drops
     0 output buffer failures, 0 output buffers swapped out
     0 carrier transitions

show run int Group-Async1     
Building configuration...


Current configuration : 113 bytes
!
interface Group-Async1
 physical-layer async
 no ip address
 encapsulation slip
 no snmp trap link-status
end