To allow the router to route TCP/IP packets, typically you need to perform router settingsand configuring an IP address and subnet mask on each interface. You also need to do router setting and configuring a dynamic routing protocol to allow the router to discover the routes in a network. That’s all what you need to do in router setting and configuration that is required to make Cisco router route IP packets. See IP routing protocols guidelines.
The following figure is a simple diagram of the WAN connection. Router settings and configuration should be done for both ends of the site. CSU/DSU at both sites typically uses the modem. The interface facing the WAN is typically the serial interface, and the interface facing the private network is typically an Ethernet interface.
Router setting #1 is connecting the serial interface to the modem. You should be familiar with the cable connection between the router serial interface and the CSU/DSU device.
Basic WAN Connection
There are many WAN cabling types. These vary from serial cables, Unshielded Twisted Pair (UTP) and fiber optic connections. Unlike standard network cable, the choice of WAN cable is dependant on the WAN service provider connection requirements.
A suitable cable and connection type must be used to match the router and WAN carriers CSU/DSU (Channel Service Unit/Data Service Unit). The CSU/DSU (also referred to as a NT or modem) provides the physical interface connection between the customer premises equipment (router) and the carrier’s line to the local loop (central office or exchange). Consult carrier documentation and router vendor documentation for cabling types and specifications.
A suitable cable and connection type must be used to match the router and WAN carriers CSU/DSU (Channel Service Unit/Data Service Unit). The CSU/DSU (also referred to as a NT or modem) provides the physical interface connection between the customer premises equipment (router) and the carrier’s line to the local loop (central office or exchange). Consult carrier documentation and router vendor documentation for cabling types and specifications.
Most connections offered by Frame Relay, X.25 and lease line carriers offer a synchronous serial connection. Some carriers offer variation on this such as Frame Relay over ISDN or dark-fiber connections. A number of serial connections exist such as V.35, RS-232, EIA/TIA-449, X.21 and HSSI. A suitable approved serial cable is thus required to connect the router to the carriers CSU/DSU.
Figure 2 is a typical V.35 WAN cable that connects the serial port of the Cisco router to the CSU/DSU device (modem).
Check also WAN technologies for more detail information about available WAN services technology.
Router setting #2 provides Ethernet connection. In business or enterprise networks, perimeter router is the first line of defense against the WAN cloud threats. The Ethernet interface of the router is typically connected to the Firewall appliance such as PIX firewall or ISA server. The firewall appliance typically has minimum two Ethernet interfaces. One Ethernet interface connects to the Ethernet interface of the perimeter router, while the other Ethernet interface connect direct to the private network.
The following diagram is typical router settings that include the perimeter router, and the firewall.
See also router connection – a basic knowledge in configuring the router.
For the following router settings and configurations, you need an optional TFTP server within the private network.
Router connection diagram
Loading Configuration Commands via TFTP Server
Router settings to load configuration commands via TFTP server, you can use the copy tftp: command.
Router1#copy tftp://172.25.1.1/NEWCONFIG running-configDestination filename [running-config]? <enter>Accessing tftp://172.25.1.1/NEWCONFIG…Loading NEWCONFIG from 172.25.1.1 (via FastEthernet0/0.1): ![OK - 24 bytes]24 bytes copied in 0.192 secs (125 bytes/sec)Router1#Generally in router setting, most people configure their routers using Telnet and the configure terminal command. For large configuration changes, people tend to resort to cutting and pasting a large set of commands. While this method works, it is inefficient and slow, particularly if you have to do the router settings and configuration to large numbers of routers. When you use TFTP to download a large set of configuration commands, the router doesn’t need to echo each character to your screen, which reduces the overhead and increases the speed.
Saving Router Configuration to Server
The other common router setting if want to store a backup copy of your router’s configuration on a TFTP server, you can use copy running-config command.
Router1>enPassword: <enablepassword>Router1#copy running-config tftp://172.25.1.1/router1-confgAddress or name of remote host [172.25.1.1]? <enter>Destination filename [router1-confg]? <enter>!!!9640 bytes copied in 3.956 secs (2437 bytes/sec)Router1#We cannot overstress the importance of making regular backups of your router setting and configuration files, and keeping copies of these files in a safe place. If a serious failure damages a router’s hardware or software, your configuration will be destroyed. Anybody who has had to reconstruct a complex router configuration file from memory can tell you how difficult and stressful this task is! But, if you have a backup of the last working configuration file, you can usually get a router working again within minutes of fixing any hardware problems.
Booting the Router Using a Remote Configuration File
You can configure router setting if you want to boot the router using an alternate configuration by using the boot network command.
The following set of commands allows you to automatically load a configuration file located on a remote TFTP server when the router boots:
Router1#configure terminalEnter configuration commands, one per line. End with CNTL/Z.Router1(config)#service configRouter1(config)#boot network tftp Network-auto 172.25.1.1Router1(config)#boot host tftp Router8-auto 172.25.1.1Router1(config)#endRouter1#By default, when the router reloads, it will read the configuration information from a file in its NVRAM. Cisco commonly refers to this file as the startup configuration file. However, you can configure the router setting to load all or part of its configuration from a remote server via TFTP. This feature does not prevent the router from loading its startup configuration from NVRAM. In fact, the router will load its local startup file before proceeding to the TFTP server files.
Storing Configuration Files Larger than NVRAM
You can configure the router setting to allow compression if your configuration file has become larger than the router’s available NVRAM.
You can compress your router setting and configuration file before saving it to NVRAM to allow you to save more configuration information. The command service compress-config will compress the configuration information when the router saves the file, and uncompress it when it is required:
Router1#configure terminalEnter configuration commands, one per line. End with CNTL/Z.Router1(config)#service compress-configRouter1(config)#endRouter1#Cisco generally ships its routers with more than enough NVRAM to store an average configuration file. However, there are times when configuration files exceed the available NVRAM. For instance, some routers contain large access lists that are hundreds of lines in length. When configuration files grow beyond the finite amount of NVRAM you will begin to have problems.
Loading a New IOS Image
You can configure the router setting to load a new IOS image if you want to upgrade the IOS image that your router uses using the Copy tftp command.
Router1#copy tftp://172.25.1.1/c2600-ik9o3s-mz.122-12a.bin flash:Destination filename [c2600-ik9o3s-mz.122-12a.bin]? <enter>Accessing tftp://172.25.1.1/c2600-ik9o3s-mz.122-12a.bin…Erase flash: before copying? [confirm] <enter>Erasing the flash filesystem will remove all files! Continue?[confirm] <enter>Erasing device… eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee
eeeeeeeeeeeeeeeee …erasedErase of flash: completeLoading c2600-ik9o3s-mz.122-12a.bin from 172.25.1.1
(via FastEthernet0/0.1):!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!![OK - 11135588 bytes]Verifying checksum… OK (0xE643)11135588 bytes copied in 82.236 secs (135410 bytes/sec)Router1# reloadProceed with reload? [confirm] <enter>
Sooner or later you will need to upgrade your router’s IOS image. Common reasons for upgrading the IOS include new features, bug fixes, and security vulnerabilities. Before you attempt to upgrade your IOS, you should save a backup copy of your current IOS to your TFTP server as discussed above.
