Part Four - Adding more routers to your lab and the purpose of the Frame Relay switch
In Part One, we went over some ways to purchase your first router. In Part Two, we looked at how to access the router, HyperTerminal, TFTP software, and Token Ring setup. In Part Three, we went over which switches you may want to purchase for your home lab. If you haven抰 read Part One, Part Two, or Part Three, click on the links at the end of this page.
In Part One we covered some routers that would work well in your startup lab, like the 2500 series or 3000 series. However, you are limited with the 2500 series or 3000 series. Eventually you抣l want to do more complex configurations and have an easy way to access all the routers in your lab without having to move the console cable from router to router. You抣l also want to simulate a frame-relay switch. You抣l want to start doing more CCNP- or CCIE-type setups. That抯 what we抣l cover in Part Four of our 揃uild A Home Lab攕eries.
Let抯 start by showing a way to allow you to access all the routers in your lab without having to move the console cable from router to router. You抣l need an 揳ccess server?router such as the Cisco 2509 or 2511 (you can also find Token Ring versions of these routers, such as a 2512, but most people will want the 2509/2511 Ethernet models). A Cisco 2509 has (1) Ethernet port, (2) Synchronous Serial ports, and (1) SCSI port for an 8 Asynchronous Serial octal cable. The 2509 will allow you to connect eight (8) devices to it. See the picture below to view a Cisco 2509 router: You could also use a Cisco 2511. This unit has (1) Ethernet, (2) Synchronous Serial ports, and (2) SCSI ports for (2) 8 Asynchronous Serial octal cables. So, the 2511 will allow you to connect sixteen (16) devices to it. See the picture below to view a Cisco 2511 router: On the above pictures of the Cisco 2509 and 2511 routers/access servers, you抣l notice the one (1) SCSI port on the left side of the 2509 and the two (2) SCSI ports on the left side of the 2511. These ports are where you would plug in what is called an octal cable. The octal cable allows you to connect numerous devices to it. For example, let抯 say you had a 2509. If you had four 2501抯 in your lab, you could connect an end of the octal cable to each of these four 2501抯 console ports and then simply Reverse Telnet into the 2509 to gain access to all the 2501抯 without having to switch a console cable from one router to another. See the picture below to view an octal cable: What is Reverse Telnet? This is another one of those so-called mysteries that no one seems to want to simply explain. Reverse Telnet allows users to Telnet through the access server (2509/2511) 搗ia a certain port range?to connect them to tty (asynchronous) lines. It can allow users to connect to the console ports of remote devices that do not natively support Telnet. Reverse Telnet is sometimes referred to as Direct Telnet. Another way to look at it is that you are initiating a Telnet session out the asynchronous line on the octal cable instead of accepting a connection into the line (which is a forward connection). For example, many of you may frequently telnet to a router through HyperTerminal. You simply use the command: Router#telnet 172.16.130.225 where 172.16.130.225 is the IP address of the router interface you抮e telnetting into (most likely a loopback address). With Reverse Telnet, you have to specify the port and line number because you抮e connecting through the 2509/2511 router to one of the asynchronous lines from the octal cable. So, you抳e got eight lines on the octal cable all plugged into the console ports of your other routers. Providing you抳e done the proper configuration on your 2509/2511, then enter the Telnet command to port 2000 + n on the access server, where n is the line number to which the other router is connected. For example, to connect to the router attached to line 2 of the octal cable, enter the following command from an EXEC session on the access server (2509/2511): Router# telnet 172.16.1.10 2002 That抯 basically what Reverse Telnet is in this particular situation.
You can also get the 2509 and 2511 routers with RJ ports instead of the SCSI ports. See the picture below to view the 2511 with RJ ports. The 2509 looks the same except it only has 8 ports: How much does the 2509 or 2511 cost? If you get the 2509 from eBay, we?ve seen them as low as $690.00. The octal cable will run you around $25.00. The 2511 is closer to $900.00. The Cisco 500-CS (Communication Server) is an inexpensive alternative to the 2509 or 2511. We抳e seen them on eBay for as low as $250.00 for the sixteen (16) port model. You can have access to up to sixteen (16) RJ45 terminal lines connected to up to sixteen (16) Cisco devices (routers, switches, etc.) through console or management ports. The Cisco 500-CS has one Ethernet port where you can telnet to it, select the Cisco device, and use it as if you are accessing the Cisco device through the console port. The 500-CS combines the following four server capabilities in one unit: Terminal server - connects asynchronous devices to a local area network (LAN) or wide area network (WAN) through network and terminal emulation software, which includes Telnet, Local Area Transport (LAT), TN3270, and Rlogin. Telecommuting server - connects devices over a telephone network using XRemote, XRemote over LAT, SLIP and compressed SLIP, and Asynchronous PPP. Protocol translator - converts one protocol to another similar protocol; the 500-CS supports Telnet, LAT, Rlogin, and TN3270 terminal emulation protocols. Asynchronous router - routes IP packets over asynchronous links using SLIP. The 500-CS supports the following routing protocols: Interior Gateway Routing Protocol (IGRP), Exterior Gateway Protocol (EGP), Border Gateway Protocol (BGP), Routing Information Protocol (RIP), and Open Shortest Path First (OSPF). The 500-CS provides bi-directional hardware flow control and modem control. In addition to the flow control, you can set the serial transmit signal voltages to either RS-232 only, or to RS-232/423 to allow for greater cabling distances. The factory default is for RS-232/423. See the picture below to view the Cisco 500-CS with 16 ports: What other routers would be good for your lab? Though expensive, the Cisco 2620 would be a good router to include. Why? Because if you plan to do intra VLAN routing using the ISL encapsulation or using a trunk, you抣l need a router that has a 100 MBPS interface. However, if you just want to route between two VLANS on the same switch then you can get away with a router with two 10 MBPS Ethernet interfaces, such as one from the 2500 series. The 2620 is a modular router that includes one (1) Fast Ethernet port that is rated at 100 MBPS. Note: the Cisco 2610 won抰 work in this case because its Ethernet interface is only 10 MBPS, like the 2500 series. See the picture below to view a Cisco 2620 router: You should also have a frame-relay switch in your lab. First, let抯 explain what this is in the simplest terms possible. In the case of your CCIE lab, a frame-relay switch is simply a router that has numerous serial ports. The more serial ports you have, the more routers you can connect to it. When someone talks about or illustrates a frame-relay network, they always draw a bunch of routers all connected to some magical cloud. What is this cloud? The cloud basically represents a service provider (like Ameritech, Sprint, etc.) network. When a packet is sent from your router to another network somewhere halfway across the country, the packet goes through your service provider抯 frame-relay switch, is sent to another one, etc. until it reaches its destination. That抯 why the service provider抯 network is illustrated as a cloud. Basically, once the packet enters the cloud (service provider抯 network), you really don抰 know the path it takes to reach its destination (unless you want to). This is what you抮e trying to simulate in your CCIE lab. You can get started with a minimum of three (3) routers to simulate a frame relay network. For example, if you had three (3) 2501 routers, it would be illustrated as follows: The configuration for the 2501 frame-relay switch would be:
version 12.0 service udp-small-servers service tcp-small-servers !
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