Basic Router Configuration Honolulu Community College Cisco Academy Training Center Semester 2 Version 2.1

Overview 1. This chapter covers general information about the router. 2. Elements of the Router. 3. Cisco Discovery Protocol. 4. Remotely accessing a router - telnet. 5. Testing network connectivity: ping trace debug

Configuration Sources n Router can be configured from: u console terminal (initial configuration). u via modem using AUX port. u virtual terminal (telnet), once configured. u TFTP server on network.

Internal Configuration Components n RAM/DRAM u Routing tables. u ARP cache. u Packet buffering u Packet queues. u Running configuration. n RAM contents lost when power is lost. n NVRAM - nonvolatile. u Backup configuration, (startup config). n NVRAM retains data when power is turned off.

Internal Configuration Components (cont) n Flash - erasable, reprogrammable ROM. u OS image & microcode. u Can have multiple copies of IOS. n Flash contents are retained when power is turned off. n ROM - read only memory. u POST (power on self test). u Bootstrap program. u Operating system software.

Internal Configuration Components n Interfaces - network connections thru which packets enter and exit the router.

Cisco Discovery Protocol (CDP) n Cisco’s proprietary command. n Allows access to configurations of directly connected routers. n Commands include: u cdp enable u show cdp interface u show cdp entry {device name} u show cdp neighbors u show cdp neighbors detail

Telnet Operations n Telnet is a virtual terminal protocol, which allows connections to hosts. n Telnet is part of the TCP/IP protocol suite. n Routers can have up to 5 simultaneous telnet sessions. n Can telnet by entering host name. n EXIT or LOGOUT to end telnet session.

Telnet tests upper-layer connectivity. Ping (ICMP)checks network connectivity (end-to-end). Trace tests each step along the way, when data is sent. Show ip route checks for a routing table entry. Show interface serial displays line and data-link protocol status.

Is Link Operational? n Interface has two components: u Hardware. u Software.

show interface serial Command n Displays line and data-link protocol status. n Line status: u triggered by Carrier Detect signal. u Physical-layer status. n Line protocol: u triggered by keepalive frames. u Data-link framing.

show interface Command n Displays statistical data about interface. n clear counters will reset counters to zero.

Debug Command n Displays the specified network events on console. n Used for troubleshooting, can significantly slow the network. n undebug all command to turn debugging off. n Debug messages can be diplayed on console, telnet terminal, UNIX host, or internal buffer. n terminal monitor command lets you redirect debug data to virtual terminal (telnet).

Summary 1 n Router modes in Cisco IOS. u User-mode: allows limited checks on configuration status. u Privileged-mode: allows detailed examination, remote access, debugging. u Global Configuration mode: make simple one line changes in config file. u Specific Configuration mode: make complex, multi-line changes in config file. u Setup mode: configuration dialog. u RXBOOT mode: password recovery.

Summary 2 n Router elements: u RAM/DRAM u NVRAM u Flash u ROM u Interfaces n CDP - to access configuration information about directly connected routers.

Summary 3 n Testing: u Telnet - layer 7, can router be accessed? u Ping - layer 3, are protocol packets being routed? (end-to-end) u Trace - tests each step along the way. u Show ip route - looks at routing table for target network table entry. n Show interface serial - checks line and protocol status. n Debug.