Verifying and Troubleshooting DHCP Configuration

Displays a list of all bindings created Displays the bindings for a specific DHCP client with an IP address of w.x.y.z Clears an automatic address binding from the DHCP server database Displays a list of all address conflicts recorded by the DHCP server Clears address conflict from the database Displays recent activity on the DHCP database Router show ip dhcp server statistics Displays a list of the number of messages sent and received by the DHCP server Router clear ip dhcp server statistics...

Troubleshooting

This chapter provides information and commands concerning the following topics Determining the gateway of last resort Determining the last routing update Interpreting the show interface command Clearing interface counters The show controllers command Operating system IP verification commands Displays a table about a specific protocol (for example, RIP or IGRP) Displays information about route w.x.y.z Displays a table of connected routes Determining the Gateway of Last Resort Router(config) ip...

Configuration Example InterVLAN Communication

Figure 13-1 illustrates the network topology for the configuration that follows, which shows how to configure inter-VLAN communication using commands covered in this chapter. Some commands used in this configuration are from previous chapters. Figure 13-3 Network Topology for Inter-VLAN Communication Configuration Figure 13-3 Network Topology for Inter-VLAN Communication Configuration Moves to interface configuration mode ISP(config-if) description simulated address representing remote website...

Cisco Discovery Protocol CDP

This chapter provides information and commands concerning the following topic Cisco Discovery Protocol (CDP) Displays global CDP information (such as timers) Displays information about neighbors Displays more detail about the neighbor device Displays information about the device named word Displays information about all devices Displays information about interfaces that have CDP running Displays information about specific interface x running CDP Displays traffic information packets in out...

Configuring the Root Switch

Switch(config) spanning-tree vlan 5 root Modifies the switch priority from the default 32768 to a lower value to allow the switch to become the root switch for VLAN 5. NOTE If all other switches have extended system ID support, this switch resets its priority to 24576. If any other switch has a priority set to below 24576 already, this switch sets its own priority to 4096 less than the lowest switch priority. If by doing this the switch would have a priority of less than 1, this command fails....

Subnetting a Class B Network Using Binary

You have a Class B address of 172.16.0.0 16. You need nine subnets. What is the IP plan of network numbers, broadcast numbers, and valid host numbers What is the subnet mask needed for this plan You cannot use N bits, only H bits. Therefore, ignore 172.16. These numbers cannot change. Step 1 Determine how many H bits you need to borrow to create nine valid subnets. 2n- 2 > 9 N 4, so you need to borrow 4 H bits and turn them into N bits. HHHHHHHHHHHHHHHH (Remove the decimal point for now) Step...

A a

Example 1 Write an ACL that prevents the 10.0 network from accessing the 40.0 network but allows everyone else to. RedDeer(config) access-list 10 deny 172.16.10.0 0.0.0.255 The standard ACL denies complete network for complete TCP IP suite of protocols. RedDeer(config) access-list 10 permit any RedDeer(config) interface fastethernet 0 0 Moves to interface configuration mode. RedDeer(config) ip access-group 10 out Applies ACL in an outbound direction. Example 2 Write an ACL that states that 10.5...

Subnetting a Class C Network Using Binary

You have a Class C address of 192.168.100.0 24. You need nine subnets. What is the IP plan of network numbers, broadcast numbers, and valid host numbers What is the subnet mask needed for this plan You cannot use N bits, only H bits. Therefore, ignore 192.168.100. These numbers cannot change. Step 1 Determine how many H bits you need to borrow to create nine valid subnets. 2n- 2 > 9 N 4, so you need to borrow 4 H bits and turn them into N bits. N 4, so you need to borrow 4 H bits and turn...

Configuring PAT Many Private to One Public Address Translation

All private addresses use a single public IP address and numerous port numbers for translation. Step 2 Define a pool of usable public IP addresses on your router that will perform NAT (optional). Use this step if you have many private addresses to translate. A single public IP address can handle thousands of private addresses. Without using a pool of addresses, you can translate all private addresses into the IP address of the exit interface (the serial link to the ISP, for example)....

Password Recovery Procedures and the Configuration Register

This chapter provides information and commands concerning the following topics Console terminal baud rate settings Changing the console line speed CLI Changing the console line speed ROM Monitor mode Password-recovery procedures for Cisco routers Password-recovery procedures for 2960 series switches The last line of output tells you what the configuration register is set to. router(config) config- register 0x2142 Changes the configuration register to 2142. The configuration register is a 16-bit...

The Enhanced Bob Maneuver for Subnetting or How to Subnet Anything in Under a Minute

Legend has it that once upon a time a networking instructor named Bob taught a class of students a method of subnetting any address using a special chart. This was known as the Bob Maneuver. These students, being the smart type that networking students usually are, added a row to the top of the chart, and the Enhanced Bob Maneuver was born. The chart and instructions on how to use it follow. With practice, you should be able to subnet any address and come up with an IP plan in under a minute....

Backing Up and Restoring Cisco IOS Software and Configurations

This chapter provides information and commands concerning the following topics Backing up configurations to a TFTP server Restoring configurations from a TFTP server Backing up the Cisco IOS Software to a TFTP server Restoring upgrading the Cisco IOS Software from a TFTP server Restoring the Cisco IOS Software from ROM Monitor mode using Xmodem Restoring the Cisco IOS Software using the ROM Monitor environmental variables and tftpdnld command Router(config) boot system flash imagename Loads the...

Security Device Manager Connecting with CLI

NOTE Cisco recommends that you use the Cisco Router and Security Device Manager (SDM) to configure your router. However, Cisco also realizes that most implementations of a router with SDM will be to use the command-line interface (CLI) for initial configuration then, after the routers have been added to the network, all future configuration will take place using SDM. If you have a router that has the SDM files already installed on it, console into the router and power the router on. If there is...

SNMP and Syslog

This chapter provides information and commands concerning the following topics Router(config) snmp-server community academy ro Sets a read-only (ro) community string called academy Router(config) snmp-server community academy rw Sets a read-write (rw) community string called Router(config) snmp-server location 2nd Floor IDF Defines an SNMP string that describes the physical location of the SNMP server Router(config) snmp-server contact Scott Empson 555-5236 Defines an SNMP string that describes...

Configuring PPP on a Serial Line Optional Commands Compression

Router(config-if) compress predictor Enables the predictor compression algorithm Enables the stac compression algorithm Configuring PPP on a Serial Line (Optional Commands) Link Quality Ensures the link has a quality of x percent. Otherwise, the link will shut down. NOTE In PPP, the Link Control Protocol allows for an optional link-quality determination phase. In this phase, the link is tested to determine whether the link quality is sufficient to bring up any Layer 3 protocols. If you use the...

Configuration Example IPv6 RIP

Figure 25-1 illustrates the network topology for the configuration that follows, which shows how to configure IPv6 and RIPng using the commands covered in this chapter. Figure 25-1 Network Topology for IPv6 RIPng Configuration Example Enables the forwarding of IPv6 unicast datagrams globally on the router Austin(config) interface fastethernet 0 0 Automatically configures an IPv6 link-local address on the interface and enables IPv6 processing on the interface Austin(config-if) ipv6 address 2001...

Static Routes in IPv6

NOTE Although not part of the CCNA exam objectives, the concept of static routes in IPv6 is one that network administrators dealing with IPv6 need to be comfortable with. NOTE To create a static route in IPv6, you use the same format as creating a static route in IPv4. Figure 25-3 illustrates the network topology for the configuration that follows, which shows how to configure static routes with IPv6. Note that only the static routes on the Austin router are displayed. Figure 25-3 Network...

Configuration Examples Frame Relay

Figure 27-1 shows the network topology for the Frame Relay configuration that follows using the commands covered in this chapter. FRAME RELAY (Atlas 550) Atlas Port Atlas Port NOTE This diagram assumes the use of an Adtran Atlas 550 device to simulate the Frame Relay cloud. Three physical ports (1 1, 2 1, and 2 2) are used to interconnect the three cities. Edmonton(config) no ip domain-lookup Turns off DNS queries so that spelling mistakes do not slow you down. Edmonton(config) enable secret...

Verifying NAT and PAT Configurations

Router clear ip nat translations inside a.b.c.d outside e.f.g.h Clears a specific translation from the table before it times out Clears the entire translation table before entries time out Troubleshooting NAT and PAT Configurations Displays information about every packet that is translated. Be careful with this command. The router's CPU might not be able to handle this amount of output and might therefore hang the system. Displays greater detail about packets being translated. Figure 23-1 shows...

Network Address Translation

This chapter provides information and commands concerning the following topics Private IP addresses RFC 1918 Configuring dynamic NAT One private to one public address translation Configuring Port Address Translation (PAT) Many private to one public address translation Configuring static NAT One private to one permanent public address translation Verifying NAT and PAT configurations Troubleshooting NAT and PAT configurations The following table lists the address ranges as specified in RFC 1918...

Creating Standard ACLs

Router(config) access-list 10 permit 172.16.0.0 0.0.255.255 Read this line to say, All packets with a source IP address of 172.16.x.x will be permitted to continue through the internetwork. Arbitrary number between 1 and 99, or 1300 and 1999, designating this as a standard IP ACL. Packets that match this statement will be allowed to continue. Source IP address to be compared to. Router(config) access-list 10 deny host 172.17.0.1 Read this line to say, All packets with a source IP address of...

Configuring a Single Cisco Router

This chapter provides information and commands concerning the following topics Entering global configuration mode Configuring a router, specifically Configuring a serial interface Configuring a Fast Ethernet interface Creating a message-of-the-day (MOTD) banner Setting the clock time zone Assigning a local host name to an IP address The no ip domain-lookup command The logging synchronous command show commands to verify the router configurations EXEC commands in configuration mode the do command...

Security Device Manager Connecting with GUI

SDM has, by default, a one-time username and password set on a router. This one-time username password combination is cisco cisco. Plug your router's first Fast Ethernet (or Gigabit Ethernet) port into a switch. Plug your PC into the same switch. Configure your PC's IP address to be 10.10.10.2 29 (10.10.10.2 with a subnet mask of 255.255.255.248). Open your PC's Internet browser and enter the following command in the browser's address bar You will see a screen similar to the one shown in Figure...

Configuration Example Ether Channel

Figure 14-2 illustrates the network topology for the configuration that follows, which shows how to configure EtherChannel using commands covered in this chapter. Figure 14-5 Network Topology for EtherChannel Configuration Figure 14-5 Network Topology for EtherChannel Configuration Turns off DNS queries so that spelling mistakes do not slow you down Changes the switch to VTP server mode Configures the VTP domain name to testdomain Creates VLAN 10 and enters VLAN configuration mode Returns to...

Configuration Example Single Area OSPF

Figure 10-1 illustrates the network topology for the configuration that follows, which shows how to configure Single Area OSPF using commands covered in this chapter. Figure 10-9 Network Topology for Single Area OSPF Configuration Network Network Figure 10-9 Network Topology for Single Area OSPF Configuration Network Network Austin(config) interface fastethernet 0 0 Moves to interface configuration mode. Austin(config-if) ip address 172.16.10.1 255.255.255.0 Austin(config-if) interface serial 0...

Single Area OSPF

This chapter provides information and commands concerning the following topics Configuring OSPF Mandatory commands Using wildcard masks with OSPF areas Configuring OSPF Optional commands Authentication Using MD5 encryption Propagating a default route Verifying OSPF configuration Configuration example Single area OSPF Configuring OSPF Mandatory Commands Starts OSPF process 123. The process ID is any positive integer value between 1 and 65,535. The process ID is not related to the OSPF area. The...