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Product Overview
IP Routing
DS2000-TS Administrator’s Guide
1 - 3
1.2.2 Reverse Terminal Server
This application has the same physical topology as the Local Terminal Server, but the communications
connection is initiated on-demand by the Serial device, rather than by the host application. This requires
that the DS2000-TS formulate a TCP/IP session request to the host on behalf of the serial device. In the
DS2000-TS, this is configured as an “Async-IP” terminal server connection, as differentiated from the more
common and default “IP-Async” terminal server connection.
1.2.3 Back-to-Back Terminal Server
This application uses two Terminal Server capabilities at both the host end and async-device end of the
connection, providing serial interfaces to both the host system and remote device. The devices may be
attached to the same DS2000-TS or to different DS2000-TSs connected over a network. Back-to-Back
terminal server allows end-to-end serial connections to be consolidated onto an all IP-oriented network
infrastructure, keeping with the spirit of “IP Convergence,” at least at the transport layer of the network. In
this configuration, the host end connection would typically use an “Async-IP” connection type, initiating the
TCP/IP session. The other industrial device would be connected to a DS2000-TS using the default “IP-
Async” Terminal Server as described above.
The principal variant of Terminal Server used with the DS2000-TS is the Local Terminal Server.
Configuration guidelines for this service are provided in Chapter 3.
1.3 IP R
OUTING
The DS2000-TS includes an integral IP router capability that enables a number of applications and
enhancements to reliability and security.
IP Routing can be used locally within a site. Local routing is an alternative to layer-2 Ethernet switching
among Ethernet ports. IP routing provides communication among devices in different Ethernet VLANs and
can provide additional network security using IP address filtering and IPsec encryption.
IP Routing is also used by the Terminal Server application described above. The Terminal Server feature
converts Async serial communications to/from IP packets. IP routing provides routing of these packets
either locally or remotely.
The default mode for IP routing uses the RIP protocol to exchange available route information with adjacent
routers. Advanced features available with IP Routing include:
• IP address filtering (selective blocking of permitted sources and destinations)
• VPNs using IPsec with DES or 3DES encryption
•
Static routing (explicit next hops, not using a routing protocol like RIP)
•
DHCP client and server (automatic assignment of IP addresses)
The Configuration Basics described in Chapter 3 deal primarily with default IP routing using RIP,
supporting Terminal Server traffic. Other IP Routing features are described primarily in the reference
sections of Appendix B.
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