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Cisco Networking Academy's Introduction to Scaling Networks

  • Sample Chapter is provided courtesy of Cisco Press.
  • Date: Apr 17, 2014.

Chapter Description

This chapter introduces strategies that can be used to systematically design a highly functional network, such as the hierarchical network design model, the Cisco Enterprise Architecture, and appropriate device selections.

Selecting Network Devices (1.2)

A basic understanding of switch and router hardware is essential to implementing network designs that scale.

Switch Hardware (1.2.1)

Cisco switches address the needs at the access, distribution, and core layers. Many models scale well with the network as it grows.

Switch Platforms (

When designing a network, it is important to select the proper hardware to meet current network requirements, as well as to allow for network growth. Within an enterprise network, both switches and routers play a critical role in network communication.

There are five categories of switches for enterprise networks, as shown in Figure 1-14:

  • Campus LAN Switches: To scale network performance in an enterprise LAN, there are core, distribution, access, and compact switches. These switch platforms vary from fanless switches with eight fixed ports to 13-blade switches supporting hundreds of ports. Campus LAN switch platforms include the Cisco 2960, 3560, 3750, 3850, 4500, 6500, and 6800 Series.
  • Cloud-Managed Switches: The Cisco Meraki cloud-managed access switches enable virtual stacking of switches. They monitor and configure thousands of switch ports over the web, without the intervention of onsite IT staff.
  • Data Center Switches: A data center should be built based on switches that promote infrastructure scalability, operational continuity, and transport flexibility. The data center switch platforms include the Cisco Nexus Series switches and the Cisco Catalyst 6500 Series switches.
  • Service Provider Switches: Service provider switches fall under two categories: aggregation switches and Ethernet access switches. Aggregation switches are carrier-grade Ethernet switches that aggregate traffic at the edge of a network. Service provider Ethernet access switches feature application intelligence, unified services, virtualization, integrated security, and simplified management.
  • Virtual Networking: Networks are becoming increasingly virtualized. Cisco Nexus virtual networking switch platforms provide secure multitenant services by adding virtualization intelligence technology to the data center network.

    Figure 1-14

    Figure 1-14 Switch Platforms

When selecting switches, network administrators must determine the switch form factors. This includes the fixed configuration shown in Figure 1-15, the modular configuration shown in Figure 1-16, the stackable configuration shown in Figure 1-17, or the nonstackable configuration.

Figure 1-15

Figure 1-15 Fixed Configuration Switches

Figure 1-16

Figure 1-16 Modular Configuration Switches

Figure 1-17

Figure 1-17 Stackable Configuration Switches

The height of the switch, which is expressed in the number of rack units, is also important for switches that are mounted in a rack. For example, the fixed configuration switches shown in Figure 1-15 are all one rack unit (1U) high.

In addition to these considerations, the following list highlights other common business considerations when selecting switch equipment:

  • Cost: The cost of a switch will depend on the number and speed of the interfaces, supported features, and expansion capability.
  • Port Density: Network switches must support the appropriate number of devices on the network.
  • Power: It is now common to power access points, IP phones, and even compact switches using Power over Ethernet (PoE). In addition to PoE considerations, some chassis-based switches support redundant power supplies.
  • Reliability: The switch should provide continuous access to the network.
  • Port Speed: The speed of the network connection is of primary concern to end users.
  • Frame Buffers: The ability of the switch to store frames is important in a network where there might be congested ports to servers or other areas of the network.
  • Scalability: The number of users on a network typically grows over time; therefore, the switch should provide the opportunity for growth.

Port Density (

The port density of a switch refers to the number of ports available on a single switch. Figure 1-18 shows the port density of three different switches.

Figure 1-18

Figure 1-18 Port Densities

Fixed configuration switches typically support up to 48 ports on a single device. They have options for up to four additional ports for small form-factor pluggable (SFP) devices. High-port densities allow for better use of limited space and power. If there are two switches that each contain 24 ports, they would be able to support up to 46 devices, because at least one port per switch is lost with the connection of each switch to the rest of the network. In addition, two power outlets are required. Alternatively, if there is a single 48-port switch, 47 devices can be supported, with only one port used to connect the switch to the rest of the network, and only one power outlet needed to accommodate the single switch.

Modular switches can support very high-port densities through the addition of multiple switch port line cards. For example, some Catalyst 6500 switches can support in excess of 1000 switch ports.

Large enterprise networks that support many thousands of network devices require high-density, modular switches to make the best use of space and power. Without using a high-density modular switch, the network would need many fixed configuration switches to accommodate the number of devices that need network access. This approach can consume many power outlets and a lot of closet space.

The network designer must also consider the issue of uplink bottlenecks: A series of fixed configuration switches can consume many additional ports for bandwidth aggregation between switches, for the purpose of achieving target performance. With a single modular switch, bandwidth aggregation is less of an issue, because the backplane of the chassis can provide the necessary bandwidth to accommodate the devices connected to the switch port line cards.

Forwarding Rates (

Forwarding rates define the processing capabilities of a switch by rating how much data the switch can process per second. Switch product lines are classified by forwarding rates, as shown in Figure 1-19.

Figure 1-19

Figure 1-19 Forwarding Rate

Entry-level switches have lower forwarding rates than enterprise-level switches. Forwarding rates are important to consider when selecting a switch. If the switch forwarding rate is too low, it cannot accommodate full wire-speed communication across all of its switch ports. Wire speed is the data rate that each Ethernet port on the switch is capable of attaining. Data rates can be 100 Mb/s, 1 Gb/s, 10 Gb/s, or 100 Gb/s.

For example, a typical 48-port gigabit switch operating at full wire speed generates 48 Gb/s of traffic. If the switch only supports a forwarding rate of 32 Gb/s, it cannot run at full wire speed across all ports simultaneously. Fortunately, access layer switches typically do not need to operate at full wire speed, because they are physically limited by their uplinks to the distribution layer. This means that less expensive, lower-performing switches can be used at the access layer, and more expensive, higher-performing switches can be used at the distribution and core layers, where the forwarding rate has a greater impact on network performance.

Power over Ethernet (

Power over Ethernet (PoE) allows the switch to deliver power to a device over the existing Ethernet cabling. This feature can be used by IP phones and some wireless access points, as shown in Figure 1-20.

Figure 1-20

Figure 1-20 Power over Ethernet

PoE allows more flexibility when installing wireless access points and IP phones, allowing them to be installed anywhere that there is an Ethernet cable. A network administrator should ensure that the PoE features are required, because switches that support PoE are expensive.

The relatively new Cisco Catalyst 2960-C and 3560-C Series compact switches support PoE pass-through, as shown in Figure 1-21.

Figure 1-21

Figure 1-21 PoE Pass-Through

PoE pass-through allows a network administrator to power PoE devices connected to the switch, as well as the switch itself, by drawing power from certain upstream switches.

Multilayer Switching (

Multilayer switches are typically deployed in the core and distribution layers of an organization’s switched network. Multilayer switches are characterized by their ability to build a routing table, support a few routing protocols, and forward IP packets at a rate close to that of Layer 2 forwarding. Multilayer switches often support specialized hardware, such as application-specific integrated circuits (ASIC). ASICs, along with dedicated software data structures, can streamline the forwarding of IP packets independent of the CPU.

There is a trend in networking toward a pure Layer 3 switched environment. When switches were first used in networks, none of them supported routing; now, almost all switches support routing. It is likely that soon all switches will incorporate a route processor because the cost of doing so is decreasing relative to other constraints. Eventually the term multilayer switch will be redundant.

As shown in Figure 1-22, the Catalyst 2960 switches illustrate the migration to a pure Layer 3 environment.

Figure 1-22

Figure 1-22 Cisco Catalyst 2960 Series Switches

With IOS versions prior to 15.x, these switches supported only one active switched virtual interface (SVI). The Catalyst 2960 also supports multiple active SVIs. This means that the switch can be remotely accessed through multiple IP addresses on distinct networks.

Router Hardware (1.2.2)

Like switches, routers can play a role in the access, distribution, and core layers of the network. In many small networks like branch offices and a teleworker’s home network, all three layers are implemented within a router.

Router Requirements (

In the distribution layer of an enterprise network, routing is required. Without the routing process, packets cannot leave the local network.

Routers play a critical role in networking by interconnecting multiple sites within an enterprise network, providing redundant paths, and connecting ISPs on the Internet. Routers can also act as a translator between different media types and protocols. For example, a router can accept packets from an Ethernet network and reencapsulate them for transport over a serial network.

Routers use the network portion of the destination IP address to route packets to the proper destination. They select an alternate path if a link goes down or traffic is congested. All hosts on a local network specify the IP address of the local router interface in their IP configuration. This router interface is the default gateway.

Routers also serve the following beneficial functions, as shown in Figure 1-23:

  • Provide broadcast containment
  • Connect remote locations
  • Group users logically by application or department
  • Provide enhanced security

    Figure 1-23

    Figure 1-23 Router Functions

With the enterprise and the ISP, the ability to route efficiently and recover from network link failures is critical to delivering packets to their destination.

Cisco Routers (

As the network grows, it is important to select the proper routers to meet its requirements. As shown in Figure 1-24, there are three categories of routers:

Figure 1-24

Figure 1-24 Router Platforms

  • Branch Routers: Branch routers optimize branch services on a single platform while delivering an optimal application experience across branch and WAN infrastructures. Maximizing service availability at the branch requires networks designed for 24x7x365 uptime. Highly available branch networks must ensure fast recovery from typical faults, while minimizing or eliminating the impact on service, and provide simple network configuration and management.
  • Network Edge Routers: Network edge routers enable the network edge to deliver high-performance, highly secure, and reliable services that unite campus, data center, and branch networks. Customers expect a high-quality media experience and more types of content than ever before. Customers want interactivity, personalization, mobility, and control for all content. Customers also want to access content anytime and anyplace they choose, over any device, whether at home, at work, or on the go. Network edge routers must deliver enhanced quality of service and nonstop video and mobile capabilities.
  • Service Provider Routers: Service provider routers differentiate the service portfolio and increase revenues by delivering end-to-end scalable solutions and subscriber-aware services. Operators must optimize operations, reduce expenses, and improve scalability and flexibility to deliver next-generation Internet experiences across all devices and locations. These systems are designed to simplify and enhance the operation and deployment of service-delivery networks.

Router Hardware (

Routers also come in many form factors, as shown in Figure 1-25. Network administrators in an enterprise environment should be able to support a variety of routers, from a small desktop router to a rack-mounted or blade model.

Figure 1-25

Figure 1-25 Routing Devices

Routers can also be categorized as fixed configuration or modular. With the fixed configuration, the desired router interfaces are built in. Modular routers come with multiple slots that allow a network administrator to change the interfaces on the router. As an example, a Cisco 1841 router comes with two Fast Ethernet RJ-45 interfaces built in and two slots that can accommodate many different network interface modules. Routers come with a variety of different interfaces, such as Fast Ethernet, Gigabit Ethernet, Serial, and Fiber-Optic.

Managing Devices (1.2.3)

Routers and switches all come with Cisco IOS Software. Network administrators are responsible for managing these devices. This includes initial configuration, verification, and troubleshooting tasks as well as maintaining up-to-date images and backing up the configuration files.

Managing IOS Files and Licensing (

With such a wide selection of network devices to choose from in the Cisco product line, an organization can carefully determine the ideal combination to meet the needs of the employees and the customers.

When selecting or upgrading a Cisco IOS device, it is important to choose the proper IOS image with the correct feature set and version. IOS refers to the package of routing, switching, security, and other internetworking technologies integrated into a single multitasking operating system. When a new device is shipped, it comes preinstalled with the software image and the corresponding permanent licenses for the customer-specified packages and features.

For routers, beginning with Cisco IOS Software Release 15.0, Cisco modified the process to enable new technologies within the IOS feature sets, as shown in Figure 1-26.

Figure 1-26

Figure 1-26 Cisco IOS Software 15 Release Family

Chapter 9, “IOS Images and Licensing,” covers more information on managing and maintaining the Cisco IOS licenses.

In-Band Versus Out-of-Band Management (

Regardless of the Cisco IOS network device being implemented, there are two methods for connecting a PC to that network device for configuration and monitoring tasks. These methods include out-of-band and in-band management, as shown in Figure 1-27.

Figure 1-27

Figure 1-27 In-Band Versus Out-of-Band Configuration Options

Out-of-band management is used for initial configuration or when a network connection is unavailable. Configuration using out-of-band management requires

  • Direct connection to console or AUX port
  • Terminal emulation client

In-band management is used to monitor and make configuration changes to a network device over a network connection. Configuration using in-band management requires

  • At least one network interface on the device to be connected and operational
  • Telnet, SSH, or HTTP to access a Cisco device

Basic Router CLI Commands (

A basic router configuration includes the host name for identification, passwords for security, assignment of IP addresses to interfaces for connectivity, and basic routing. Assuming that the physical interfaces are connected to the network, Example 1-1 shows the commands entered to enable a router with OSPF. Verify and save configuration changes using the copy running-config startup-config command.

Example 1-1 Enabling a Router with OSPF

Router# configure terminal
Router(config)# hostname R1
R1(config)# enable secret class
R1(config)# line con 0
R1(config-line)# password cisco
R1(config-line)# login
R1(config-line)# exec-timeout 0 0
R1(config-line)# line vty 0 4
R1(config-line)# password cisco
R1(config-line)# login
R1(config-line)# exit
R1(config)# service password-encryption
R1(config)# banner motd $ Authorized Access Only! $
R1(config)# interface GigabitEthernet0/0
R1(config-if)# description Link to LAN 1
R1(config-if)# ip address
R1(config-if)# no shutdown
R1(config-if)# interface Serial0/0/0
R1(config-if)# description Link to R2
R1(config-if)# ip address
R1(config-if)# clock rate 128000
R1(config-if)# no shutdown
R1(config-if)# interface Serial0/0/1
R1(config-if)# description Link to R3
R1(config-if)# ip address
R1(config-if)# no shutdown
R1(config-if)# router ospf 10
R1(config-router)# router-id
R1(config-router)# network area 0
R1(config-router)# network area 0
R1(config-router)# network area 0
R1(config-router)# end
R1# copy running-config startup-config

Example 1-2 shows the results of the configuration commands that were entered in Example 1-1. To clear the router configuration, use the erase startup-config command and then the reload command.

Example 1-2 Router Running Configuration

R1# show running-config
Building configuration...

Current configuration : 1242 bytes
Version 15.1
Service timestamps debug datetime msec
Service timestamps log datetime msec
Service password-encryption
hostname R1
enable secret class
<output omitted>
interface GigabitEthernet0/0
 description Link to LAN 1
 ip address
 no shutdown
interface Serial0/0/0
 description Link to R2
 ip address
 clock rate 128000
 no shutdown
interface Serial0/0/1
 description Link to R3
 ip address
 no shutdown
router ospf 10
 network area 0
 network area 0
 network area 0
banner motd ^C Authorized Access Only! ^C
line console 0
 password cisco
 exec-timeout 0 0
Line aux 0
line vty 0 4
 password cisco

Basic Router show Commands (

Here are some of the most commonly used IOS commands to display and verify the operational status of the router and related network functionality. These commands are divided into several categories.

The following show commands are related to routing:

  • show ip protocols: As shown in Example 1-3, this command displays information about the routing protocols configured. If OSPF is configured, this includes the OSPF process ID, the router ID, networks the router is advertising, the neighbors the router is receiving updates from, and the default administrative distance, which is 110 for OSPF.

    Example 1-3 show ip protocols Command

    R1# show ip protocols
    Routing Protocol is "ospf 10"
      Outgoing update filter list for all interfaces is not set
      Incoming update filter list for all interfaces is not set
      Router ID
      Number of areas in this router is 1. 1 normal 0 stub 0 nssa
      Maximum path: 4
      Routing for Networks: area 0 area 0 area 0
      Passive Interface(s):
      Routing Information Sources:
        Gateway         Distance      Last Update              110      00:11:48              110      00:11:50              110      00:11:50
      Distance: (default is 110)
  • show ip route: As shown in Example 1-4, this command displays routing table information, including routing codes, known networks, administrative distance and metrics, how routes were learned, next hop, static routes, and default routes.

    Example 1-4 show ip route Command

    R1# show ip route
    Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
           D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
           N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
           E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
           i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
           * - candidate default, U - per-user static route, o - ODR
           P - periodic downloaded static route
    Gateway of last resort is not set
     is variably subnetted, 5 subnets, 3 masks
    C is directly connected, GigabitEthernet0/0
    L is directly connected, GigabitEthernet0/0
    O [110/65] via, 01:43:03, Serial0/0/0
    C is directly connected, Serial0/0/0
    L is directly connected, Serial0/0/0
    O [110/65] via, 01:43:03, Serial0/0/1 is variably subnetted, 3 subnets, 2 masks
    C is directly connected, Serial0/0/1
    L is directly connected, Serial0/0/1
    O [110/128] via, 01:43:03, Serial0/0/0
                            [110/128] via, 01:43:03, Serial0/0/1
  • show ip ospf neighbor: As shown in Example 1-5, this command displays information about OSPF neighbors that have been learned, including the Router ID of the neighbor, the priority, the state (Full = adjacency has been formed), the IP address, and the local interface that learned of the neighbor.

    Example 1-5 show ip ospf neighbor Command

    R1# show ip ospf neighbor
    Neighbor ID    Pri    State       Dead Time    Address         Interface          0    FULL/   -   00:00:34      Serial0/0/0          0    FULL/   -   00:00:34    Serial0/0/1

The following show commands are related to interfaces:

  • show interfaces: As shown in Example 1-6, this command displays interfaces with line (protocol) status, bandwidth, delay, reliability, encapsulation, duplex, and I/O statistics. If specified without a specific interface designation, all interfaces will be displayed. If a specific interface is specified after the command, information about that interface only will be displayed.

    Example 1-6 show interfaces Command

    R1# show interfaces
    GigabitEthernet0/0 is up, line protocol is up (connected)
      Hardware is CN Gigabit Ethernet, address is 00e0.8fb2.de01 (bia 00e0.8fb2.de01)
      Description: Link to LAN 1
      Internet address is
      MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
         reliability 255/255, txload 1/255, rxload 1/255
    <output omitted>
    Serial0/0/0 is up, line protocol is up (connected)
      Hardware is HD64570
      Description: Link to R2
      Internet address is
      MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,
         reliability 255/255, txload 1/255, rxload 1/255
      Encapsulation HDLC, loopback not set, keepalive set (10 sec)
      Last input never, output never, output hang never
      Last clearing of "show interface" counters never
    <output omitted>
    Serial0/0/1 is up, line protocol is up (connected)
      Hardware is HD64570
      Description: Link to R3
      Internet address is
      MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,
         reliability 255/255, txload 1/255, rxload 1/255
      Encapsulation HDLC, loopback not set, keepalive set (10 sec)
      Last input never, output never, output hang never
      Last clearing of "show interface" counters never
  • show ip interfaces: As shown in Example 1-7, this command displays interface information, including protocol status, IP address, whether a helper address is configured, and whether an ACL is enabled on the interface. If specified without a specific interface designation, all interfaces will be displayed. If a specific interface is specified after the command as shown in Example 1-7, information about that interface only will be displayed.

    Example 1-7 show ip interface Command

    R1# show ip interface gigabitEthernet 0/0
    GigabitEthernet0/0 is up, line protocol is up
      Internet address is
      Broadcast address is
      Address determined by setup command
      MTU is 1500 bytes
      Helper address is not set
      Directed broadcast forwarding is disabled
      Multicast reserved groups joined:
      Outgoing access list is not set
      Inbound  access list is not set
      Proxy ARP is enabled
      Local Proxy ARP is disabled
      Security level is default
      Split horizon is enabled
      ICMP redirects are always sent
      ICMP unreachables are always sent
      ICMP mask replies are never sent
      IP fast switching is enabled
      IP fast switching on the same interface is disabled
      IP Flow switching is disabled
      IP CEF switching is enabled
      IP CEF switching turbo vector
      IP multicast fast switching is enabled
      IP multicast distributed fast switching is disabled
      IP route-cache flags are Fast, CEF
      Router Discovery is disabled
      IP output packet accounting is disabled
      IP access violation accounting is disabled
      TCP/IP header compression is disabled
      RTP/IP header compression is disabled
      Policy routing is disabled
      Network address translation is disabled
      BGP Policy Mapping is disabled
      Input features: MCI Check
      IPv4 WCCP Redirect outbound is disabled
      IPv4 WCCP Redirect inbound is disabled
      IPv4 WCCP Redirect exclude is disabled
  • show ip interface brief: As shown in Example 1-8, this command displays all interfaces with IP addressing information and interface and line protocol status.

    Example 1-8 show ip interface brief Command

    R1# show ip interface brief
    Interface            IP-Address     OK?  Method   Status                   Protocol
    GigabitEthernet0/0     YES  manual   up                       up
    GigabitEthernet0/1   unassigned     YES  unset    administratively down    down
    Serial0/0/0     YES  manual   up                       up
    Serial0/0/1   YES  manual   up                       up
    Vlan1                unassigned     YES  unset    administratively down    down
  • show protocols: As shown in Example 1-9, this command displays information about the routed protocol that is enabled and the protocol status of interfaces.

    Example 1-9 show protocols Command

    R1# show protocols
    Global values:
      Internet Protocol routing is enabled
    GigabitEthernet0/0 is up, line protocol is up
      Internet address is
    GigabitEthernet0/1 is administratively down, line protocol is down
    Serial0/0/0 is up, line protocol is up
      Internet address is
    Serial0/0/1 is up, line protocol is up
      Internet address is
    Vlan1 is administratively down, line protocol is down

Other connectivity-related commands include the show cdp neighbors command shown in Example 1-10.

Example 1-10 show cdp neighbors Command

R1# show cdp neighbors
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
                  S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone
Device ID  Local Intrfce   Holdtme Capability      Platform    Port ID
S1         Gig 0/0           126         S        2960        Gig 1/1
R2         Ser 0/0/0         136         R        C1900       Ser 0/0/0
R3         Ser 0/0/1         133         R        C1900       Ser 0/0/0

This command displays information on directly connected devices, including Device ID, local interface that the device is connected to, capability (R = router, S = switch), platform, and Port ID of the remote device. The details option includes IP addressing information and the IOS version.

Basic Switch CLI Commands (

Basic switch configuration includes the host name for identification, passwords for security, and assignment of IP addresses for connectivity. In-band access requires the switch to have an IP address. Example 1-11 shows the commands entered to enable a switch.

Example 1-11 Enable a Switch with a Basic Configuration

Switch# enable
Switch# configure terminal
Switch(config)# hostname S1
S1(config)# enable secret class
S1(config)# line con 0
S1(config-line)# password cisco
S1(config-line)# login
S1(config-line)# line vty 0 4
S1(config-line)# password cisco
S1(config-line)# login
S1(config-line)# service password-encryption
S1(config)# banner motd $ Authorized Access Only! $
S1(config)# interface vlan 1
S1(config-if)# ip address
S1(config-if)# no shutdown
S1(config-if)# ip default-gateway
S1(config)# interface fa0/2
S1(config-if)# switchport mode access
S1(config-if)# switchport port-security
S1(config-if)# end
S1# copy running-config startup-config

Example 1-12 shows the results of the configuration commands that were entered in Example 1-11.

Example 1-12 Switch Running Configuration

S1# show running-config
<some output omitted>
version 15.0
service password-encryption
hostname S1
enable secret 4 06YFDUHH61wAE/kLkDq9BGho1QM5EnRtoyr8cHAUg.2
interface FastEthernet0/2
 switchport mode access
 switchport port-security
interface Vlan1
 ip address
ip default-gateway
banner motd ^C Authorized Access Only ^C
line con 0
 exec-timeout 0 0
 password 7 1511021F0725
line vty 0 4
 password 7 1511021F0725
line vty 5 15

Verify and save the switch configuration using the copy running-config startup-config command. To clear the switch configuration, use the erase startup-config command and then the reload command. It might also be necessary to erase any VLAN information using the delete flash:vlan.dat command. When switch configurations are in place, view the configurations using the show running-config command.

Basic Switch show Commands (

Switches make use of common IOS commands for configuration, to check for connectivity, and to display current switch status. For example, the following commands are useful for gathering some important information:

  • show port-security interface: Displays any ports with security activated. To examine a specific interface, include the interface ID, as shown in Example 1-13. Information included in the output: the maximum addresses allowed, current count, security violation count, and action to be taken.

    Example 1-13 show port-security interface Command

    S1# show port-security interface fa0/2
    Port Security               : Enabled
    Port Status                 : Secure-up
    Violation Mode              : Shutdown
    Aging Time                  : 0 mins
    Aging Type                  : Absolute
    SecureStatic Address Aging  : Disabled
    Maximum MAC Addresses       : 1
    Total MAC Addresses         : 1
    Configured MAC Addresses    : 0
    Sticky MAC Addresses        : 0
    Last Source Address:Vlan    : 0024.50d1.9902:1
    Security Violation Count    : 0
  • show port-security address: As shown in Example 1-14, this command displays all secure MAC addresses configured on all switch interfaces.

    Example 1-14 show port-security address Command

    S1# show port-security address
                   Secure Mac Address Table
    Vlan    Mac Address       Type                       Ports   Remaining Age
    ----    -----------       ----                       -----   -------------
       1    0024.50d1.9902    SecureDynamic               Fa0/2        -
    Total Addresses in System (excluding one mac per port)     : 0
    Max Addresses limit in System (excluding one mac per port) : 1536
  • show interfaces: As shown in Example 1-15, this command displays one or all interfaces with line (protocol) status, bandwidth, delay, reliability, encapsulation, duplex, and I/O statistics.

    Example 1-15 show interfaces Command

    S1# show interfaces fa0/2
    FastEthernet0/2 is up, line protocol is up (connected)
      Hardware is Fast Ethernet, address is 001e.14cf.eb04 (bia 001e.14cf.eb04)
      MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec,
         reliability 255/255, txload 1/255, rxload 1/255
      Encapsulation ARPA, loopback not set
      Keepalive set (10 sec)
      Full-duplex, 100Mb/s, media type is 10/100BaseTX
      input flow-control is off, output flow-control is unsupported
      ARP type: ARPA, ARP Timeout 04:00:00
      Last input 00:00:08, output 00:00:00, output hang never
      Last clearing of "show interface" counters never
      Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
      Queueing strategy: fifo
      Output queue: 0/40 (size/max)
      5 minute input rate 0 bits/sec, 0 packets/sec
      5 minute output rate 2000 bits/sec, 3 packets/sec
         59 packets input, 11108 bytes, 0 no buffer
         Received 59 broadcasts (59 multicasts)
         0 runts, 0 giants, 0 throttles
         0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
         0 watchdog, 59 multicast, 0 pause input
         0 input packets with dribble condition detected
         886 packets output, 162982 bytes, 0 underruns
         0 output errors, 0 collisions, 1 interface resets
         0 unknown protocol drops
         0 babbles, 0 late collision, 0 deferred
         0 lost carrier, 0 no carrier, 0 pause output
         0 output buffer failures, 0 output buffers swapped out
  • show mac-address-table: As shown in Example 1-16, this command displays all MAC addresses that the switch has learned, how those addresses were learned (dynamic/static), the port number, and the VLAN assigned to the port.

    Example 1-16 show mac address-table Command

    S1# show mac address-table
              Mac Address Table
    Vlan    Mac Address       Type        Ports
    ----    -----------       --------    -----
     All    0100.0ccc.cccc    STATIC      CPU
     All    0100.0ccc.cccd    STATIC      CPU
     All    0180.c200.0000    STATIC      CPU
     All    0180.c200.0001    STATIC      CPU
     All    0180.c200.0002    STATIC      CPU
     All    0180.c200.0003    STATIC      CPU
     All    0180.c200.0004    STATIC      CPU
     All    0180.c200.0005    STATIC      CPU
     All    0180.c200.0006    STATIC      CPU
     All    0180.c200.0007    STATIC      CPU
     All    0180.c200.0008    STATIC      CPU
     All    0180.c200.0009    STATIC      CPU
     All    0180.c200.000a    STATIC      CPU
     All    0180.c200.000b    STATIC      CPU
     All    0180.c200.000c    STATIC      CPU
     All    0180.c200.000d    STATIC      CPU
     All    0180.c200.000e    STATIC      CPU
     All    0180.c200.000f    STATIC      CPU
     All    0180.c200.0010    STATIC      CPU
     All    ffff.ffff.ffff    STATIC      CPU
       1    001e.4915.5405    DYNAMIC     Fa0/3
       1    001e.4915.5406    DYNAMIC     Fa0/4
       1    0024.50d1.9901    DYNAMIC     Fa0/1
       1    0024.50d1.9902    STATIC      Fa0/2
       1    0050.56be.0e67    DYNAMIC     Fa0/1
       1    0050.56be.c23d    DYNAMIC     Fa0/6
       1    0050.56be.df70    DYNAMIC     Fa0/3
    Total Mac Addresses for this criterion: 27

Like the router, the switch also supports the show cdp neighbors command.

The same in-band and out-of-band management techniques that apply to routers also apply to switch configuration.

6. Summary (1.3) | Next Section Previous Section

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