A customer who still used old terminals and DOS PC's wanted to move away from a Frame Relay setup where two remote offices connect through Digi C/Con serial boxes. They put in Verizon Business DSL at each office, and we also installed Multitech VPN Routers at each location, and Digi Terminal Servers. Digi has made terminal servers for some time, but the old product looked like the C/Cons while these are smaller and look more like a switch. The review of the older portserver still applies with some small differences.
You connect to these serially at 9600 baud (default is root with password dbps) on any port to login and set the config:
set config ip=192.168.2.10 set config dhcp=off set config gateway=192.168.2.1
As dhcp is on by default, you could also just telnet to the box.
Each box will need the gateway set to its router. So, if we have a three office vpn, we might have 192.168.1.0 as the main office network, 192.168.2.0 as one branch, and 192.168.3.0 as the other (see the Multitech review for specifics on setting up the VPN's). The TS at the first branch would be 192.168.2.10 and its gateway might be 192.168.2.1.
In addition, the Unix box needs routing - it needs routes for 192.168.2.0 and 192.168.3.0. Those would point at its router: 192.168.1.1 in this case. If it already has a default route pointing to the router, you of course don't need these. If you don't understand routing, see Routing Basics.
We installed the Digi "RealPort" software and then used "drpadmin" to assign tty devices to specific ip addresses. This then lets you use port 3 on the 192.168.2.10 device as (for example) /dev/ttyg03. You can use stty and "ditty" commands, add ttyg03 to inittab, etc. - it just assigns fake tty ports to the device so that it can all be transparent to your software. We made the assignments match the existing serial setups, so terminals and printers just automatically worked without reconfiguring software.
One thing I noticed is that if the TS is reset, it takes a LONG time before logins work again. I thought things weren't working because I had no logins even after the devices responded to pings. A minute or so later everything was fine, so just have patience.
These provide a simple way to transition old systems to a network. The cost of the terminal servers is less than replacing the old equipment with PC's. As old terminals and DOS machines are replaced with new pc's, the customer can leave them connected serially or connect them with TCP/IP.
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More Articles by Tony Lawrence © 2012-11-18 Tony Lawrence
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