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The SR Multiplexer and Cisco routers can be configured to allow SR Multiplexers to co-exist with LAN traffic on a frame relay wide area network. This is useful for cut-overs when moving from a multiplexer based WAN to one based on TCP/IP peers. It also allows PC based LAN traffic to use the same frame relay WAN with RS-232 traffic.
Cut-overs: This is quite useful for cut-overs. When moving a multiplexer-based WAN to a frame-relay based TCP/IP WAN, this method can be used to minimize cut-over down time and the need for overlapping wide area communication facilities.
Bandwidth sharing between RS-232 and TCP/IP traffic: This technique allows the sharing of bandwidth between TCP/IP and RS-232 traffic. Remote offices that need the LAN connectivity for email and file transfers along with RS-232 connectivity for a host-based service will benefit from reduced cost, no duplicated facilities, and higher performance on the RS-232 system.
Legacy Applications: Running character-based UNIX applications from a remote host while using LAN based internetworking adds greatly to system flexibility. This removes the need to run special TCP/IP stacks on local PC's, configuration of host minicomputers, and expensive PC reconfiguration when moving to LAN based applications.
Out-of-Band Network Management: Allows remote network management using RS-232 access switch products to share bandwidth on the WAN. This has some drawbacks, since there is no connectivity when the network is down, but is useful for remote management of many devices such as hubs, switching hubs, and servers.
The test bed configuration used Cisco 2501 routers, each configured with two serial ports and one LAN port, two SR multiplexers with frame-relay firmware, and appropriate DSU's (two DCB FT-1's) as show in figure one.
1. The SR multiplexers were configured with all defaults, including AUTO sensing the frame relay management type. Port configuration is unimportant for this demonstration.
2. The Cisco routers were configured as in Listing One and Listing Two. For this demonstration, no IP routing is shown.
3. After connections were completed, test the circuit by performing remote test loops on the SR multiplexers. Using the Testing Tools menu, measure round-trip delay and verify that the multiplexers loop back QBF messages.
1. The Cisco router must provide clock for the multiplexer. Use Cisco cable #
CAB232FC between the router and multiplexer.
router25>enable router25#show config Using 544 out of 32762 bytes ! version 10.3 service tcp-small-servers ! hostname router25 ! frame-relay switching ! interface Ethernet0 no ip address shutdown ! interface Serial0 no ip address encapsulation frame-relay frame-relay lmi-type q933a frame-relay type nni frame-relay route 17 interface Serial1 16 ! interface Serial1 no ip address encapsulation frame-relay clockrate 56000 frame-relay lmi-type ansi frame-relay intf-type dce frame-relay route 16 interface Serial0 17 ! line con 0 line aux 0 transport input all line vty 0 4 login ! end
router28#show config Using 710 out of 32762 bytes ! version 10.3 service config service tcp-small-servers ! hostname router28 ! no ip routing frame-relay switching ! interface Ethernet0 no ip address no ip route-cache shutdown ! interface Serial0 no ip address encapsulation frame-relay no ip route-cache frame-relay lmi-type q933a frame-relay intf-type nni frame-relay route 17 interface Serial1 16 ! interface Serial1 no ip address encapsulation frame-relay no ip route-cache clockrate 56000 frame-relay intf-type dce frame-relay route 16 interface Serial0 17 ! line con 0 exec-timeout 0 0 line aux 0 transport input all line vty 0 4 login ! end router28#