Dialup Network In A Box

This is a self-contained, portable telephony network which allows us to connect and analog modems and ISDN adapters at retrocomputing events.

The setup (as of Q4/2019) consists of:
  • Auerswald COMmander Basic2 PBX with 8x S0 (ISDN BRI) ports, 16x a/b (analog) ports, 8x Up0 (ISDN) ports and 1x S2M (E1 ISDN PRI)
  • 1U Rack-Mount Atom PC with 4-port E1 (DAHDI) card and FreeSwitch: Emulates public telephone exchange
  • Livingston Portmaster 3 RAS with ability to terminate 30 ISDN or analog modem calls

Telephony Setup

The physical setup looks like this:

Logical Setup:

This shows the logical setup including PCs and associated software:


Ethernet Switch configuration

We have an old 16-port gigabit ethernet switch (DELL PowerConnect 2716) in our setup.

VLAN 1 (admin)

  • Port 1: untagged
  • Port 7: PC eth1 (tagged)
  • Port 8: admin laptop (tagged)

VLAN 11 (admin)

This is a "jumper" from VLAN 1 (untagged) to VLAN 11 (tagged) as the switch doesn't natively support its web interface on a tagged IP

  • Port 4: untagged
  • Port 7: PC eth1 (tagged)
  • Port 8: admin laptop (tagged)

VLAN 3999 (uplink)

  • Ports 9..16
  • Port 8: admin laptop (tagged)

VLAN 4000 (auerswald)

  • Port 2: Auerswald (untagged)
  • Port 7: PC eth1 (tagged)
  • Port 8: admin laptop (tagged)

VLAN 4001 (PM3)

  • Port 3: PM3 (untagged)
  • Port 7: PC eth1 (tagged)
  • Port 8: admin laptop (tagged)

E1 configuration

E1 ports on the atom1u machine with DAHDI + freeswitch

The ports are allocated as follows:

  • Port E1/1: Auerswald
  • Port E1/2: PM3
  • Port E1/3: Unused
  • Port E1/4: Unused

The ports, as well as those of the portsmaster + auerswald are brougiht out on the keystone patch panel. They must be connected as stated above using E1 cross-over cables. those have a special pin-out, and are not to be confused with Ethernet cables (straight or cross-over).

IP Network configuration

VLAN 1/11 (admin)

IP Host dell2716 switch admin laptop atom1u

VLAN 3999 (uplink)

IP Host
DHCP atom1u

VLAN 4000 (auerswald)

IP Host Auerswald Commander Basic2 atom1u

VLAN 4001 (PM3)

IP Host Livingston Portmaster 3 telnet/rlogin host (atom1u) default-gw (atom1u) PPP lease pool

Updated by laforge almost 2 years ago · 7 revisions

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