Cisco Routers for the Desperate: Router and Switch Management, the Easy Way
Michael W. Lucas
Format: PDF / Kindle (mobi) / ePub
Cisco routers and switches are the cornerstones of many networks. But when things break, repairs can intimidate even the most competent administrator. Luckily, just knowing the "in case of emergency" basics will take you far.
Just like the original, this second edition of the highly acclaimed Cisco Routers for the Desperate is written for the administrator in crisis mode. Updated to cover switches and the latest Cisco terminology, with a tighter focus on the needs of the small network administrator, this second edition gives you what you need to know to provide reliable network services and fix problems fast. You'll find coverage of:
- Installation—how to get your router and network connections up and running right the first time
- Troubleshooting routers and switches, so that you can determine whether your hardware or the Internet is broken
- Security concerns, like how to keep your network equipment safe from hackers and install a private network between two offices
- How to implement basic network redundancy to reduce the risk of network downtime
Cisco Routers for the Desperate, 2nd Edition is designed to be read once and left alone until something breaks. When it does, you'll have everything you need to know in one easy-to-follow guidebook.
schedule a two-hour (or longer!) window of acceptable downtime for a router upgrade. IOS Installation After all of this work, the new IOS installation itself is almost anticlimactic. Just copy the image from the SCP server to the router's internal flash. router# copy scp://username@servername/new-image-name flash:new-image-name The copy command will prompt you for confirmation. If the internal flash is too small to hold both the old image and the new image, it will ask you if you want to
always reached via one provider and check its BGP information. Here, we've chosen to check the BGP information on the system 22.214.171.124. router# sho ip b 126.96.36.199 BGP routing table entry for 188.8.131.52/24, version 4521114 Paths: (2 available, best #1, table Default-IP-Routing-Table) Not advertised to any peer 300 400 172.16.0.2 from 172.16.0.2 (184.108.40.206) Origin IGP, metric 0, localpref 100, valid, external, best Community: 190972324 190973904 190974904 200 600 500 10.1.8.5
network has a MAC (Media Access Control) address, also known as a hardware address. A MAC address is a unique 48-bit hexadecimal number. Any Cisco device will display the ARP table with the show arp command. Switch>sho arp Protocol Address Age (min) Hardware Addr Type Interface Internet 10.184.0.243 14 0019.b9f0.ace1 ARPA Vlan1 Internet 10.184.0.248 207 0004.23ce.45d7 ARPA Vlan1 Internet 10.184.0.254 207 0004.23ce.45d7 ARPA Vlan1 ... Here, we see the IP address of each host in the ARP
secret, and disabling the enable password, is much like setting a front door password. Unlike the front door passwords, which can be different for each line, the enable passwords work globally. router# conf t router(config)# enable secret your-secret-password router(config)# no enable password When you're in standard configure mode , the command enable secret and a password string will set the enable secret. You don't want any sort of easily retrievable password on any system, so be sure to
addresses are issued in blocks that are multiples of two. If you have 5 bits to play with, you'll have 32 (2 x 2 x 2 x 2 x 2 = 32) IP addresses on your network, and your netmask will be a /27 (32 – 5 = 27). If you have 8 bits for your hosts, you have (28) or 256 IP addresses. If you're told that you have 55 IP addresses, you're either sharing a network with other people or you need to learn what your network administrator is drinking and get him to share. UNUSABLE IP ADDRESSES The first and