Enterasys Networks Security Router X-PeditionTM - Manual (Page 108)

General IP Features
5-6 Configuring IP
does not actually examine or store full routing tables sent by routing devices, it merely keeps track
of which systems are sending such data. Using IRDP, the XSR can specify both a priority and the
time after which a device should be assumed down if no further packets are received.
The XSR enables router discovery and associated values with the ip irdp command. The router
also supports the redirection of packets routed through the same port they were received on with
the
ip redirect command.
TCP
The Transmission Control Protocol (TCP) is a transport layer language providing a connection-
oriented, reliable, byte-stream service described by RFC-793.
UDP
The User Datagram Protocol (UDP) is a simple, datagram-oriented, transport layer protocol where
each operation by a process produces exactly one UDP datagram, which causes one IP datagram
to be sent. RFC-768 describes UDP.
Telnet
Telnet provides a general, bi-directional, 8-bit byte-oriented communications facility that is
always enabled on the XSR. It is a standard method by which terminal devices and terminal-
oriented processes interface, as described by RFC-854. A Telnet connection is a TCP connection
used to transmit data with interspersed Telnet control data. Two entities compose a Telnet link:
• A Telnet server is the host which provides some service
• A Telnet user is the host which initiates communications
Telnet port (23) and server settings can be configured on the XSR with the ip telnet port and
ip telnet server commands. You can also configure Telnet client service to other servers with
the telnet ip_address command. Refer to the XSR CLI Reference Guide for more information.
SSH
The Secure Shell (SSH) protocol provides for safe remote login and other network services on the
XSR. Along with a user-supplied client, the SSHv2 server allows you to establish a secure
connection, similar to that provided by an inbound Telnet connection with an important
exception.
Unlike Telnet, SSH encrypts the entire connection with the XSR to hide your identity, provides
data confidentiality via the negotiated choice of encryption types such as 3DES, and offers
message integrity through hashing using SHA-1 or other algorithms such as MD5 or crypto
library support for third-party encryption ciphers such as Blowfish, Twofish, AES, CAST and
ARCfour. Enabled (by default) on the CLI with the
ip ssh server command, SSH is further
configured by specifying users, passwords, privilege level and policy with the aaa user ,
password , privilege 15 and policy commands, the idle timeout interval for your SSH session
with the session-timeout ssh command, and user authentication with the aaa SSH command.
Upon configuring the XSR for the first time, you should generate a host key pair with the crypto
key dsa command, otherwise, if no key is generated, the default key is used for any connection
request. Generated host keys are encrypted and stored in the hostkey.dat file within Flash where
the file cannot be read or copied. All SSH connection requests use the host keys stored in the