LAN Switching Foundation Technologies

10/100BASE-T Autonegotiation The finer points of autonegotiation have been discussed; however, some drawbacks need to be discussed. Numerous network problems resulted when the autonegotiation feature was first deployed. The issues ranged from degradation in performance to connectivity loss. The cause ... [full story]

100BASE-T Autonegotiation The following is the command that configures a switch to autonegotiate a port: set port speed auto In Figure 1-9, Host1 has a 10BASE-T card. The switch has a capability to operate in both 10BASE-T and 100BASE-T ... [full story]

239.1.1.1 Is Accepted by Ports 3/1 and 7/3Switch3 (enable) show cam static 2 * = Static Entry. + = Permanent Entry. # = System Entry. R = Router Entry. X = P ort Security Entry VLAN ... [full story]

A New Connection Between Switches The following steps outline how Switch3 chooses a new RP:Step 1. A new connection between Switch1 and Switch3 has been set up. Step 2. Switch3 receives a better BPDU from Switch1. It keeps the ... [full story]

Access Layer Link Failure Because traffic from Host 1 is being sent to the active HSRP address on SW-D1 to be routed, when the link between SW-A2 and SW-D1 fails, SW-D1 recognizes a path in its routing table to VLAN ... [full story]

Addition of a Link Between SW-D1 and SW-D2 The link between SW-D1 and SW-D2 continues the VLAN numbering convention by using VLAN 906, and a dynamic routing neighbor relationship is formed between SW-D1 and SW-D2 using this link. As a ... [full story]

Address Aliasing Address aliasing is defined as mapping 32 multicast IP addresses to a single Layer 2 MAC address. A multicast Layer 3 address could map to a system MAC address that is used by the switch, which is a potential ... [full story]

Adjacency Information Off the Routermsfc_15#show adjacency detail Protocol Interface Address IP Vlan3 ... [full story]

Advertisement Request An advertisement request is sent when a switch has rebooted, the domain name has been changed, or the VTP summary revision number is higher than what is locally on the switch. As noted in Example 4-4, the switch is ... [full story]

Aging In addition to the MAC address and the associated port, a bridge also records the time that the device was learned. Aging of learned MAC addresses allows the bridge to adapt to moves, adds, and changes of devices to the ... [full story]

An Ounce of Planning Everyone has probably heard the old joke "ready, fire, aim." Unfortunately, this phrase can sometimes describe the implementation of some networks given what appears to be a lack of basic planning prior to configuration. The daily operation ... [full story]

Assigning an IP Address to VLAN 10SW1-MSFC3#config terminal Enter configuration commands, one per line. End with CNTL/Z. SW1-MSFC3(config)#interface vlan10 SW1-MSFC3(config-if)#ip address 10.10.10.1 255.255.255.0 SW1-MSFC3(config-if)#no shut After the IP address is configured and the ... [full story]

Automated Conversion Tools The configuration conversion tool is available as a link from the Software Center page on cisco.com. This tool allows users to paste in the configuration of a switch running Catalyst OS and see the resulting command equivalents under ... [full story]

Autonegotiation Autonegotiation is a mechanism that allows two devices at either end to negotiate speed and duplex settings at physical layer. The benefits of autonegotiation include minimal configuration and operability between dissimilar Ethernet technologies. In today's networks, 10BASE-T and 100BASE-T are ubiquitous. ... [full story]

Autonegotiation Configurations for 10/100 Ethernet Configuration NIC (Speed/Duplex) Configuration Switch (Speed/Duplex) Resulting NIC Speed/Duplex Resulting Catalyst Speed/Duplex Comments AUTO AUTO 100 Mbps, Full duplex 100 Mbps, Full duplex Assuming maximum capability of Catalyst switch and NIC is 100 full duplex. 100 Mbps, Full duplex AUTO 100 Mbps, Full duplex 100 Mbps, Half duplex Duplex mismatch. AUTO 100 ... [full story]

Autonegotiations Configurations for Gigabit Ethernet Switch Port Gigabit Autonegotiation Setting NIC Gigabit Autonegotiation Setting Switch Link/NIC Link Enabled Enabled Up Up Disabled Disabled Up Up Enabled Disabled Down Up Disabled Enabled Up Down Network engineers still have heated discussions about whether to enable autonegotiation in the network. As mentioned earlier, autonegotiation is a big advantage for mobile users. A user ... [full story]

Autostate Hybrid and native switches have a feature called autostate. The feature is enabled by default and can only be disabled in hybrid. In hybrid, logical VLAN interfaces configured on the RSM/RSFC, MSFC, or Layer 3 module on the Catalyst 4000 ... [full story]

BackboneFast BackboneFast is a Maxage optimizer. (See Figure 10-6.) In other words, BackboneFast helps get rid of the 20 seconds that are associated with Maxage timer, which is used for indirect failures as mentioned in the previous section. BackboneFast does this ... [full story]

BPDU Entering MST Region The objective of having an IST is to make the MST region appear as a single bridge. This is an important distinction because it allows for MST to have large Layer 2 networks. For instance, Region ... [full story]

BPDU Traffic Seen on Portfast BPDU Guard PortSwitch2 (enable) 2003 Oct 07 15:30:32 %SPANTREE-2-RX_PORTFAST: Received BPDU on PortFast enable port. Disabling 3/1 Switch2 (enable) show port 3/1 Port Name ... [full story]

Bridge Protocol Data Unit Format [View full size image] Spanning Tree Port Transitions and Timers Part of the STP algorithm and process of building a loop-free network, as well as reconfiguration on a topology change, is to cycle the bridge ports through ... [full story]

Bridge1 Floods Traffic [full story]

Bridging Loop In this basic example, there are redundant links without STP. This creates a bridged loop. In this case, the redundant links cause the Ethernet data frame to have more than ... [full story]

Broadcasts and Multicasts With Ethernet, broadcasts are specialized frames that are destined for all devices on an Ethernet network. Broadcasts use a MAC address of FF-FF-FF-FF-FF-FF. This is a special MAC address because it is the highest number allowed in the ... [full story]

Buffering Data Frames must wait their turn for the central arbiter before being transmitted in shared bus architectures. Frames can also potentially be delayed when congestion occurs in a crossbar switch fabric. As a result, frames must be buffered until transmitted. ... [full story]

Building Blocks When designing a switched network, following a modular approach is a good practice. These modules can be thought of as the building blocks of an overall network. After the design and configuration of the basic building blocks are well ... [full story]

Calculating MAC Address for Multicast Group Port 10/1 is configured to accept the 239.1.1.1 stream on VLAN 3. (See Example 9-2.) All other ports should not receive this traffic anymore because the CAM table has only one port associated with ... [full story]

CAM and TCAM The terms CAM and ternary CAM (TCAM) have become almost interchangable with today's switches because all the switching architectures discussed in this chapter are capable of making switching decisions using Layer 3 and Layer 4 information, along with ... [full story]

CAM Entries Do Not Have Multicast MAC AddressesSwitch2 (enable) show cam system 3 * = Static Entry. + = Permanent Entry. # = System Entry. R = Router Entry. X = Port Security Entry $ = Dot1x Security ... [full story]

Campus Design Although it is difficult to capture a "typical" campus network design in a single illustration, campus networks, in general, experience many common demands including support of large numbers of end users, servers, and the need for WAN connectivity to ... [full story]

Catalyst 3750 (Lord of the Rings) Components and Architecture One of the newest members of the Catalyst family of switches is the 3750 series, codename Lord of the Rings. The 3750 series is made up of fixed-configuration switches allowing expansion through ... [full story]

Catalyst 3750 Redundancy The Catalyst 3750 switching platform is capable of high availability by design, given the stackable architecture. You can stack and interconnect up to nine switches in a self-healing ring. Failover on the 3750 series is less than 1 ... [full story]