DHCP

Accessing Remote Devices

Accessing Remote Devices Topics Cisco Discovery Protocol (CDP) Telnet Slide 1 of 1 Purpose: This slide state the objectives Emphasize: Discuss the objectives with the students.

Cisco Discovery Protocol Upper-Layer Entry Addresses TCP/IP Novell IPX AppleTalk Others Cisco Proprietary Data-Link Protocol CDP discovers and shows information about directly connected Cisco devices Media Frame Relay LANs ATM Others A data-link proprietary protocol that provides information about directly connected Cisco switches, routers, and other devices CDP discovers neighbor devices regardless of which protocol suite they are running Slide 1 of 1 Purpose: Emphasize: Note: CDP is sent using multicast frame with the MAC address 0100.0ccc.cccc.

Discovering Neighbors with CDP Runs on routers with Cisco IOS 10.3 or later and Cisco switches and hubs Summary information includes: Device identifiers Address list Port identifier Capabilities list Platform CDP Slide 1 of 1 Purpose: Emphasize: CDP is media- and protocol-independent and runs on all Cisco-manufactured equipment including routers, access servers, switches and some managed hubs. With CDP, network management applications can retrieve the device type and SNMP agent address of neighboring devices. This capability enables applications to send SNMP queries to neighboring devices. CDP allows network management applications to dynamically discover Cisco devices that are neighbors. CDP runs on all media that support Subnetwork Access Protocol, including LAN and Frame Relay. CDP runs over the data link layer only, not the network layer. Therefore, two systems that support different network-layer protocols can learn about each other. Cached CDP information is available to network management applications. Cisco devices never forward a CDP packet. When new information is received, old information is discarded. The holdtime determines how long to keep existing information from a neighbor. CDP CDP show cdp

Using CDP SwitchA RouterA RouterB SwitchB S1 S0 10.1.1.2 10.1.1.1 10.3.3.2 10.3.3.1 10.2.2.1 10.2.2.2 RouterA#sh cdp ? entry Information for specific neighbor entry interface CDP interface status and configuration neighbors CDP neighbor entries traffic CDP statistics <cr> RouterA(config)#no cdp run RouterA(config)#interface serial0 RouterA(config-if)#no cdp enable Slide 1 of 1 Purpose: Emphasize: Note: Some of the CDP commands are not available on the Cat 1900 switch, like “cdp run”, “show cdp traffic”, and “show cdp entry”.

Using the show cdp neighbor Command SwitchA RouterA RouterB SwitchB S1 S0 10.1.1.2 10.1.1.1 10.3.3.2 10.3.3.1 10.2.2.1 10.2.2.2 RouterA#sh cdp neighbors Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge S - Switch, H - Host, I - IGMP, r - Repeater Device ID Local Intrfce Holdtme Capability Platform Port ID RouterB Ser 0 148 R 2522 Ser 1 SwitchA Eth 0 167 T S 1900 2 Slide 1 of 1 Purpose: Emphasize: This graphic shows the show cdp neighbors command initiated from a router, which displays a summary of the capabilities and access details for the CDP neighbors. The show cdp neighbors detail command shows detailed information about the same devices. Note: If the neighbor is a Cat 1900 switch, the switch mac address is also displayed. If the switch is a 2900xl, its mac address is not displayed.

Using the show cdp entry Command SwitchA RouterA RouterB SwitchB S1 S0 10.1.1.2 10.1.1.1 10.3.3.2 10.3.3.1 10.2.2.1 10.2.2.2 RouterA#sh cdp entry * ------------------------- Device ID: RouterB Entry address(es): IP address: 10.1.1.2 Platform: cisco 2522, Capabilities: Router Interface: Serial0, Port ID (outgoing port): Serial1 Holdtime : 168 sec Version : Cisco Internetwork Operating System Software IOS (tm) 2500 Software (C2500-JS-L), Version 12.0(3), RELEASE SOFTWARE (fci) Copyright (c) 1986-1999 by cisco Systems, Inc. Compiled Mon 08-Feb-99 18:18 by phanguye Slide 1 of 1 Purpose: Emphasize: The example shows what information can be obtained about RouterA’s neighbor. CDP is one way to learn about other Cisco devices on the network.

Additional CDP Commands SwitchA RouterA RouterB SwitchB S1 S0 10.1.1.2 10.1.1.1 10.3.3.2 10.3.3.1 10.2.2.1 10.2.2.2 RouterA#sh cdp traffic CDP counters : Packets output: 56, Input: 38 Hdr syntax: 0, Chksum error: 0, Encaps failed: 3 No memory: 0, Invalid packet: 0, Fragmented: 0 RouterA#sh cdp interface BRI0 is administratively down, line protocol is down Encapsulation HDLC Sending CDP packets every 60 seconds Holdtime is 180 seconds Slide 1 of 1 Purpose: Emphasize: Note: The holdtime indicates how long the neighbor information will be kept in the local CDP table.

Using Telnet to Connect to Remote Devices SwitchA RouterA RouterB SwitchB S1 S0 10.1.1.2 10.1.1.1 10.3.3.2 10.3.3.1 10.2.2.1 10.2.2.2 RouterA#telnet 10.2.2.2 Trying 10.2.2.2 ... Open ------------------------------------------------- Catalyst 1900 Management Console Copyright (c) Cisco Systems, Inc. 1993-1998 All rights reserved. Enterprise Edition Software Ethernet Address: 00-90-86-73-33-40 PCA Number: 73-2239-06 PCA Serial Number: FAA02359H8K Model Number: WS-C1924-EN System Serial Number: FAA0237X0FQ . SwitchB> Slide 1 of 1 Purpose: Emphasize: Another way to learn about a remote device is to connect to it. Telnet, a virtual terminal protocol that is part of the TCP/IP protocol suite, allows connections to remote hosts. By default, a router can have up to five simultaneous incoming Telnet sessions. With Cisco’s implementation of TCP/IP, you need not enter the connect or telnet command to establish a Telnet connection. If you prefer, you can just enter the learned host name, the router will resolve the hostname using DNS or a local host table. To end a Telnet session, use the exit or logout EXEC command. These are alternate commands for the operations listed on the graphic: Initiate a session: Denver> connect paris Denver> paris Denver> 131.108.100.152 Resume a session (enter session number or name): Denver> 1 Paris> End a session: Paris> exit Note: The Cat 1900 can accept incoming telnet connections but can not initiate an outgoing telnet session. Remote device

Viewing Telnet Connections SwitchA RouterA RouterB SwitchB S1 S0 10.1.1.2 10.1.1.1 10.3.3.2 10.3.3.1 10.2.2.1 10.2.2.2 RouterA#sh session Conn Host Address Byte Idle Conn Name 1 10.1.1.2 10.1.1.2 0 1 10.1.1.2 * 2 10.3.3.2 10.3.3.2 0 0 10.3.3.2 RouterA#sh user Line User Host(s) Idle Location * 0 con 0 10.1.1.2 3 10.3.3.2 2 11 vty 0 idle 1 10.1.1.2 Slide 1 of 1 Purpose: Emphasize: Note: This output was taken from a 2522. Line 11 = VTY 0. You can send messages to one or all terminal lines. A common reason for doing this is to inform users of an impending shutdown. To send a message to other terminals, issue the following command: send {line-number | *} Syntax Description line-number Specifies the line number to which the message will be sent. * Indicates that the message will be sent to all lines. The system prompts for the message, which can be up to 500 characters long. End the message by entering Ctrl-Z. Enter Ctrl-C to abort the command.

Suspending a Telnet Session SwitchA RouterA RouterB SwitchB S1 S0 10.1.1.2 10.1.1.1 10.3.3.2 10.3.3.1 10.2.2.1 10.2.2.2 RouterB#<Ctrl-Shift-6>x RouterA#sh session Conn Host Address Byte Idle Conn Name 1 10.1.1.2 10.1.1.2 0 1 10.1.1.2 RouterA#resume 1 RouterB# Slide 1 of 1 Purpose: Emphasize: The key stoke sequence for Ctrl-Shift-6 and x.

Closing a Telnet Session SwitchA RouterA RouterB SwitchB S1 S0 10.1.1.2 10.1.1.1 10.3.3.2 10.3.3.1 10.2.2.1 10.2.2.2 RouterA#disconnect Closing connection to 10.3.3.2 [confirm] RouterA#clear line 11 [confirm] [OK] Closing the current session opened by you to a remote device Slide 1 of 1 Purpose: Emphasize: Note: Disconnect without the session number disconnect that last active session. Closing a session opened by a remote device to you

Using the ping and trace Commands Router##ping 10.1.1.10 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 10.1.1.10, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/4 ms Router#trace 10.1.1.10 Tracing the route to 10.1.1.10 1 10.1.1.10 4 msec 4 msec 4 msec Router# Slide 1 of 1 Purpose: Emphasize: As you use CDP and Telnet you should note the information retrieved from the devices you successfully contacted. Documenting that information helps put the network into a visual perspective, and can be referenced at a later time. This concludes the network discovery portion of the chapter. In the next section, we will discuss configuration file and IOS image management. Test connectivity and path to a remote device

Review Questions 1. What CDP command is used to get information about one specific neighbor? 2. What key combination suspends a Telnet session? Slide 1 of 1 Purpose: Emphasize: Refer to the appendix for the answers to the review questions.