SLIP (Serial Line Internet Protocol) and PPP instructions
This document contains instructions on how to go about getting a SLIP or
PPP address and using SLIP or PPP on the SCS Cisco terminal servers
(TS[5/6/7/8].SRV.CS.CMU.EDU). SLIP and PPP connections are supported from
high speed modems. The "man dialup" command on a
CS/RI/EDRC-supported workstation or time-sharing system contains information
such as phone numbers to dial and how to use the Cisco terminal servers.
SLIP and PPP encapsulate IP datagrams using an escape byte. IP packets normally
travel over 10 megabit/sec ethernet. With SLIP and PPP, they are traversing a link
whose bandwidth might typically be less than 20 kilobits/sec. Thus, many
IP-based applications might not work adequately over SLIP and PPP links. SLIP and PPP can
support some TELNET sessions, and a modest FTP. While NFS and AFS might
work, their use over SLIP and PPP is strongly discouraged.
If you need an IP address for SLIP and PPP
Using "dynamic" IP addresses:
If you don't need a dedicated IP address, you can use the default IP address
assigned to the line you've dialed into. This means that you likely won't get
the same IP addressed assigned each time you dial in, but most SLIP and PPP
clients can parse and/or negotiate with the server to set the dynamic IP
address on the client.
When you dial up the V.32bis or V.34 huntgroup, log in as you normally would
with Kerberos ID and password. At the "TS?> prompt, type the command
"slip default" to activate SLIP, or "ppp default" to activate PPP.
The server will then print out information about the connection including
the IP address assigned.
Requesting dedicated IP addresses:
If you need a hostname and/or IP address for a SLIP or PPP client, run the
/usr/cs/bin/netregister program and use the 'add' command at the prompt.
You will then be prompted for information about the host.
A response for the following fields is mandatory:
Example - Remarks: SLIP and PPP use, modem, Encrypted password string for
hostname is "sGl79TRXp1Y3U"
"netregister" will send mail to
Within a couple of days,
you will receive an e-mail response containing the IP address in addition to
If you don't have access to the netregister program, complete the
form found in
send it to email@example.com.
If you have an existing hostname/IP address
If you presently have a machine with an existing hostname and IP address, it
is preferable that you ask for a new hostname/IP address or request a new IP
address for that hostname. The SLIP and PPP clients are assigned IP addresses on
certain subnets only.
To use SLIP and PPP with the SCS Cisco terminal servers
The following instructions outline how to use SLIP and PPP with the SCS Cisco
terminal servers. It is assumed the SLIP or PPP clients that were netregistered
have suitable SLIP or PPP implementations and that you are familiar with its operation.
- Read about
how to use the Cisco terminal server command interface.
- At the "TS>" prompt, type:
where hostname is the first component of the hostname. The server will
prompt you with "Password:". Type the password (see below for
instructions on getting a password) or just carriage return if a password
has not been enabled. You should then see:
Entering SLIP mode.
Your IP address is 128.2.nnn.nnn, MTU is 1524 bytes
- If you want a password enabled for your SLIP or PPP connection, please follow
this procedure (until something more formal is implemented):
Run the following program:
/afs/cs/project/systems-parker/slip/bin/@sys/gentacpass [-a | -g] hostname
@sys supported are:
Whether you select your password or have one generated, the program will
print the following line:
Encrypted password string for hostname is "sGl79TRXp1Y3U"
You should send this output in an e-mail message to
to have your password updated/activated.
Back to Computing Facilities Home Page
For help with any facilities-related problem,
or if you have questions and comments
regarding Facilities documentation, please send mail to