16 Quick Guide - SLIP Server

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Configuring your Linux machine as a SLIP server is a deceptively simple thing to do. The actual process is simple, but there are a number of different aspects to the configuration and understanding how each of the stages interact with each other is what will help you diagnose any problems you experience. Here are the steps that you must follow to configure your Linux machine as a SLIP server:

  1. Assemble your hardware. Avoid IRQ and shared memory conflicts. Test each of the serial ports by connecting a dumb terminal to each of the ports and use a null modem cable and a comms program like minicom or seyon to talk to each. Make sure you can send and receive characters. If you intend running a number of serial ports then try to use a smart serial board or use 16550AFN UARTs. This will help ease some of the work of handling interrupts generated by the serial ports.
  2. Build your kernel, make sure it has networking configured, IP Forwarding enabled, and SLIP configured. Make sure you configure CSLIP if you wish to use it. Double check you have IP Forwarding enabled.
  3. Install your kernel. Test the kernel. Check the /proc/net/dev file and make sure that you have sl0 and other SLIP devices listed. If not then you have probably made some error in configuring your kernel, or you are not actually running your new kernel.
  4. Configure a getty on the serial port(s) that you wish to use for your incoming calls. You should refer to the Serial-HOWTO for a description of how to do this. Remember to configure your modem so that the DCD pin tracks received carrier, this is how your getty will detect an incoming call.
  5. Test the getty to make sure it works. It is important that you do this before you start worrying about the actual SLIP configuration. Try dialing into your system, you should get a login: prompt and be able to login normally.
  6. Decide how you want your server to allocate addresses. If you want your users to get the same address each time they call then you want a static server, if you want to minimise the number of addresses you use and don't care what address your users are allocated then you want a dynamic server.
  7. Decide how you are going to build the SLIP server, whether you are going to use SLIPlogin, dip or dSLIP. If you wish to use the SLIPlogin package then refer to the SLIP Server using SLIPlogin section. If you are going to use dip then refer to section SLIP Server using DIP . If you want to build your SLIP server using the dSLIP package then refer to section SLIP Server using dSLIP . Ensure you have the appropriate software, it is a recent version and compile the software if necessary.
  8. If the addresses you are allocating to you SLIP users are part of your ethernet network, then make sure you read the Proxy ARP section and configure a proxy arp for each address. You may do this in the /etc/SLIPlogin and /etc/SLIPlogout files if you are using the SLIPlogin package. If the addresses you are allocating are from a network separate to your ethernet network then you can use either proxy arp or gated. If you use gated then refer to the gated section.
  9. Test your SLIP server.

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