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This chapter describes how to use the command-line interface (CLI) to configure the Fast Ethernet ports on the supervisor engine module, the Ethernet switching module, and the Fast Ethernet switching module. This chapter also contains information on such features as the Spanning-Tree Protocol and CLI Ethernet connectivity.
Ethernet and Fast Ethernet switching modules share the following features:
For additional information on all commands discussed in this chapter, refer to the Catalyst 5000 Series Command Reference publication.
The default values of the Ethernet and Fast Ethernet module features are as follows:
To customize the Ethernet ports, complete the tasks in the following sections.
You can assign names to all ports on the Ethernet and Fast Ethernet modules. It may be particularly useful to assign names to the Fast Ethernet ports on the supervisor engine module to facilitate switch administration.
To assign a name to a port, perform the following task in privileged mode:
| Task | Command |
|---|---|
| Assign a name to a port. | set port name mod_num/port_num [name_string] |
After entering the set port name command, you see a display similar to the following:
Console> (enable) set port name 1/1 Router Connection Port 1/1 name set. Console> (enable) set port name 1/2 Server 1 Port 1/2 name set.
To verify that you set the port name correctly, enter the show port mod_num/port_num command. You see this display:
Console> (enable) show port Port Name Status Vlan Level Duplex Speed Type ---- -------------------- -------- -------- ------ ------ ----- ------- 1/1 Router Connection ready 2 high half 100 100BaseTX 1/2 Server 1 ready 1 high half 100 100BaseTX 2/1 ready 10 normal half 10 10BaseT 2/2 disabled 10 normal half 10 10BaseT 2/3 connect 10 normal half 10 10BaseT 2/4 connect 10 normal half 10 10BaseT . . . 2/23 0 0 0 0 0 0 2/24 0 0 0 0 0 0 Port Align-Err FCS-Err Xmit-Err Rcv-Err ---- ---------- ---------- ---------- ---------- 1/1 0 0 0 0 1/2 1 0 0 0 2/1 0 0 0 0 2/2 0 0 0 0 2/3 0 0 0 0 2/4 30 0 0 0 2/5 0 0 0 0 2/6 0 0 0 0 2/7 0 0 0 0 2/8 0 0 0 0 2/9 0 0 0 0 2/10 0 0 0 0 2/11 0 0 0 0 2/12 0 0 0 0 Port Single-Col Multi-Coll Late-Coll Excess-Col Carri-Sens Giants ---- ---------- ---------- ---------- ---------- ---------- ---------- 1/1 0 0 0 0 0 0 1/2 680 418 0 1 0 - 2/1 756 99 0 0 0 0 2/2 0 0 0 0 0 0 2/3 0 0 0 0 0 0 2/4 409 403 0 11 0 1256 2/5 0 0 0 0 0 0 2/6 0 0 0 0 0 0 2/7 0 0 0 0 0 0 2/8 0 0 0 0 0 0 2/9 0 0 0 0 0 0 2/10 0 0 0 0 0 0 2/11 0 0 0 0 0 0 2/12 0 0 0 0 0 0 Last-Time-Cleared -------------------------- Thu Jun 8 1995, 07:58:06 Console> (enable)
To set the priority level, perform this task in privileged mode:
| Task | Command |
|---|---|
| Configure the priority level for each port. | set port level mod_num/port_num normal | high |
After entering the set port level command, you see this display:
Console> (enable) set port level 1/1 high Port 1/1 level set to high. Console> (enable) set port level 1/2 high Port 1/2 level set to high.
To verify that the port priority level is correct, enter the show port mod_num/port_num command. After entering this command, you see a display similar to the verification example in the section "Setting the Port Name."
To set the port speed for a port, perform this task in privileged mode:
| Task | Command |
|---|---|
| Set the port speed of a port. | set port speed mod num/port num [10 | 100 | auto] |
After entering the set port speed mod num/port num [10 | 100 | auto] command, you see this display:
Console> (enable) set port speed Usage: set port speed<10|100|auto> Console> (enable) set port speed 2/1 auto Port 2/1 speed set to auto-sensing mode. Console> (enable) set port speed 2/2 10 Port 2/2 speed set to 10 Mbps. Console> (enable) set port speed 2/3 100 Port 2/3 speed set to 100 Mbps.
To verify that you set the port speed correctly, enter the show port mod_num/port_num command. After entering this command, you see a display similar to the verification example in the section "Setting the Port Name."
Set the transmission type to full or half duplex for the ports that will be used.
To set the transmission type of a port, perform this task in privileged mode:
| Task | Command |
|---|---|
| Set the transmission type of a port. | set port duplex mod num/port num full | half |
After entering the set port duplex command, you see this display:
Console> (enable) set port duplex 2/1 half Port 2/1 set to half-duplex. Console> (enable) set port duplex 2/2 half Port 2/2 set to half-duplex.
To verify that you set the transmission type correctly, enter the show port mod_num/port_num command. After entering this command, you see a display similar to the verification example in the section "Setting the Port Name."
To check connectivity using the ping command, perform these steps:
| Task | Command |
|---|---|
| Step 1 Send an echo request from the Catalyst 5000 series switch to the host. | ping host |
| Step 2 If the host is unresponsive, check the configuration for the IP address of the Catalyst 5000 series switch and default IP route. | show interface
show ip route |
After entering the ping command, you see this display:
Console> (enable) ping 171.69.192.3 171.69.192.3 is alive
Sample results of using the ping command are as follows:
You can configure the specialized features in this section on your Ethernet and Fast Ethernet modules.
The packets are not forwarded by the switches participating in the Spanning-Tree Protocol, but instead are used by the switches to identify the loop-free path. Spanning-Tree Protocol performs this function for Catalyst 5000 series switches. The default configuration has all Spanning-Tree Protocols enabled.
To configure Spanning-Tree Protocol, perform this task:
| Task | Command |
|---|---|
| Enable Spanning-Tree Protocol. | set spantree enable [vlan] |
After enabling Spanning-Tree Protocol, you see this display:
Console> (enable) set spantree enable 1 VLAN1 bridge spanning tree enabled Console< (enable)
To disable Spanning-Tree Protocol, enter the set spantree disable command. To set the bridge forward delay for a VLAN, enter the set spantree fwddelay delay [vlan] command. For more information on Spanning-Tree Protocol commands, refer to the Catalyst 5000 Series Command Reference publication.
To display all spanning-tree information, enter the show spantree command.
Console> show spantree ?
Usage: show spantree [vlan]
show spantree
Console> (enable) show spantree 1 VLAN 1 Spanning tree enabled Designated Root 00-1f-00-40-0b-90-c9-00 Designated Root Priority 45 Designated Root Cost 0 Designated Root Port 1/0 Root Max Age 20 sec Hello Time 2 sec Forward Delay 20 sec Bridge ID MAC ADDR 00-40-0b-90-c9-00 Bridge ID Priority 45 Bridge Max Age 20 sec Hello Time 2 sec Forward Delay 20 sec Port Vlan Port-State Cost Priority Fast-Start -------- ---- ------------- ----- -------- ---------- 1/1 1 forwarding 19 32 disabled 2/3 1 not-connected 100 32 disabled 2/4 1 not-connected 100 32 disabled 2/5 1 not-connected 100 32 disabled 2/6 1 not-connected 100 32 disabled 2/7 1 not-connected 100 32 disabled 2/8 1 forwarding 100 32 disabled 2/9 1 not-connected 100 32 disabled 2/10 1 not-connected 100 32 disabled 2/11 1 not-connected 100 32 disabled 2/12 1 not-connected 100 32 disabled 2/13 1 Learning 100 32 disabled 2/14 1 not-connected 100 32 disabled 2/15 1 not-connected 100 32 disabled 2/16 1 not-connected 100 32 disabled 2/17 1 not-connected 100 32 disabled 2/18 1 not-connected 100 32 disabled 2/19 1 not-connected 100 32 disabled 2/20 1 not-connected 100 32 disabled 2/21 1 not-connected 100 32 disabled 2/22 1 not-connected 100 32 disabled 2/23 1 not-connected 100 32 disabled 2/24 1 not-connected 100 32 disabled 4/13-24 1 not-connected 100 32 disabled 4/25-36 1 not-connected 100 32 disabled 4/37-48 1 not-connected 100 32 disabled Console> (enable)
Use these commands to perform additional Spanning-Tree Protocol functions:
| Task | Command |
|---|---|
| Disable the Spanning-Tree Protocol algorithm for a VLAN. | set spantree disable [vlan] |
| Set the bridge forward delay for a VLAN. | set spantree fwddelay delay [vlan] |
| Set the bridge hello time for a VLAN. | set spantree hello interval [vlan] |
| List the available set spantree commands. | set spantree help |
| Set the bridge maximum aging time for a VLAN. | set spantree maxage agingtime [vlan] |
| Set the bridge path cost for a port. | set spantree portcost mod_num/port_num cost |
| Allow a port that is connected to a single workstation or PC to start faster. | set spantree portfast mod_num/port_num {enable | disable} |
| Set the bridge priority for a port in spanning-tree algorithm. | set spantree portpri mod_num/port_num priority |
| Assign a lower path cost to a set of VLANs on a port. | set spantree portvlancost mod_num/port_num [cost cost] [vlan_list] |
| Set the port priority for a subset of VLANs in the trunk port. | set spantree portvlanpri mod_num/port_num priority [vlans] |
| Set the bridge priority for a VLAN. | set spantree priority bridge_priority [vlan] |
| Set a primary or secondary root for specific VLANs or for all allowed VLANs on the switch. | set spantree root [secondary] [vlan_list] [dia network_diameter] [hello hello_time] |
| Enable/disable fast switchover to alternate ports when the root port fails. | set spantree uplinkfast {enable| disable} [rate station_update_rate] |
You can design fault-tolerant connections using Ethernet only or Ethernet combined with other topologies. Figure 4-1 and Figure 4-2 show fault-tolerant Fast Ethernet topologies using the Spanning-Tree Protocol.
Multiple active paths between stations cause loops in the network. If a loop exists in the network topology, the potential exists for duplicate messages. When loops occur, some switches see stations appear on both sides of the switch. This condition confuses the forwarding algorithm and allows duplicate frames to be forwarded.
To provide path redundancy, Spanning-Tree Protocol defines a tree that spans all switches in an extended network. Spanning-Tree Protocol forces certain redundant data paths into a standby (blocked) state. If one network segment in the Spanning-Tree Protocol becomes unreachable, or if Spanning-Tree Protocol costs change, the spanning-tree algorithm reconfigures the spanning-tree topology and reestablishes the link by activating the standby path.
Spanning-Tree Protocol operation is transparent to end stations, which are unaware whether they are connected to a single LAN segment or a switched LAN of multiple segments.
All switches in an extended LAN participating in Spanning-Tree Protocol gather information on other switches in the network through an exchange of data messages called Bridge Protocol Data Units (BPDUs). This exchange of messages results in the following actions:
The Spanning-Tree Protocol root switch is the logical center of the spanning-tree topology in a switched network. All paths that are not needed to reach the root switch from anywhere in the switched network are placed in Spanning-Tree Protocol backup mode. Table 4-1 describes the root switch variables that affect the entire spanning-tree performance.
| Variable | Description |
|---|---|
Hello Time | Determines how often the switch broadcasts its hello message to other switches. |
| Maximum Age Timer | Measures the age of the received protocol information recorded for a port and ensures that this information is discarded when its age limit exceeds the value to the maximum age parameter recorded by the switch. The timeout value for this timer is the maximum age parameter of the switches. |
| Forward Delay Timer | Monitors the time spent by a port in the learning and listening states. The timeout value is the forward delay parameter of the switches. |
BPDUs contain information about the transmitting switch and its ports, including switch and port Media Access Control (MAC) addresses, switch priority, port priority, and port cost. The Spanning-Tree Protocol uses this information to elect the root switch and root port for the switched network, as well as the root port and designated port for each switched segment.
Figure 4-3 shows how BDPUs enable a Spanning-Tree Protocol topology.
The stable active topology of a switched network is determined by the following:
Each configuration BPDU contains the following minimal information:
The switch sends configuration BPDUs to communicate and compute the spanning-tree topology. A MAC frame conveying a BPDU sends the switch group address to the destination address field. All switches connected to the LAN on which the frame is transmitted receive the BPDU. BPDUs are not directly forwarded by the switch, but the information contained in the frame can be used to calculate a BPDU by the receiving switch, and, if the topology changes, instigate a BPDU transmission.
A BPDU exchange results in the following:
If all switches are enabled with default settings, the switch with the lowest MAC address in the network becomes the root switch. The network in Figure 4-4 assumes that Switch A has the lowest MAC address and is therefore the root switch. However, due to traffic patterns, number of forwarding ports, or line types, Switch A might not be the ideal root switch. By increasing the priority (lowering the numerical priority number) of the ideal switch so that it becomes the root switch, you force a Spanning-Tree Protocol recalculation to form a new, stable topology.
When the stable Spanning-Tree Protocol topology is based on default parameters, the path between source and destination stations in a switched network might not be the most ideal. For instance, connecting higher speed links to a port that has a higher number than the current root port can cause a root-port change. The point is to make the fastest link the root port.
For example, assume that port 2 on Switch B in Figure 4-5 is a fiber-optic link, and that port 1 on Switch B (a UTP link) is the root port. Network traffic might be more efficiently handled over the high-speed fiber-optic link. By changing the Port Priority parameter for port 2 to a higher priority (lower numerical value) than port 1, port 2 becomes the root port. The same change can occur by changing the Port Cost parameter for port 2 to a lower value than that of port 1.
Each port on a switch using Spanning-Tree Protocol exists in one of the following five states:
A port moves through these five states as follows:
Figure 4-6 illustrates how a port moves through the five states.
You can modify each port state by using management software. When Spanning-Tree Protocol is enabled, every switch in the network goes through the blocking state and the transitory states of listening and learning at power up. If properly configured, the ports then stabilize to the forwarding or blocking state.
When the spanning-tree algorithm decides to place a port in the forwarding state, the following occurs:
A port in the blocking state does not participate in frame forwarding, as shown in Figure 4-7. After initialization, a BPDU is sent to each port in the switch. A switch initially assumes it is the root until it exchanges BPDUs with other switches. This exchange establishes which switch in the network is really the root. If only one switch resides in the network, no exchange occurs, the forward delay timer expires, and the ports move to the listening state. A switch always enters the blocking state following switch initialization.
A port in the blocking state performs as follows:
The listening state is the first transitional state a port enters after the blocking state, when Spanning-Tree Protocol determines that the port should participate in frame forwarding. Learning is disabled in the listening state. Figure 4-8 shows a port in the listening state.
A port in the listening state performs as follows:
A port in the learning state is preparing to participate in frame forwarding. This is the second transitional state through which a port moves in anticipation of frame forwarding. The port enters the learning state from the listening state through the operation of Spanning-Tree Protocol.
A port in the learning state performs as follows:
A port in the forwarding state forwards frames, as shown in Figure 4-9. The port enters the forwarding state from the learning state through the operation of Spanning-Tree Protocol.
A port in the forwarding state performs as follows:
 | Caution Use the immediate-forwarding (portfast) mode only on ports connected to individual workstations to allow these ports to come up and go directly to the forwarding state, rather than having to go through the entire spanning-tree initialization process. To prevent illegal topologies, enable Spanning-Tree Protocol on ports connected to switches or other devices that forward messages. |
A port in the disabled state does not participate in frame forwarding or the operation of Spanning-Tree Protocol, as shown in Figure 4-10. A port in the disabled state is virtually nonoperational.
A disabled port performs as follows:
The Spanning-Tree Protocol Fast Uplink Switchover feature, also called UplinkFast, provides fast convergence after a spanning-tree topology change and achieves load balancing between redundant links using uplink groups. An uplink group is a set of ports (per VLAN), only one of which is forwarding at any given time. Specifically, an uplink group consists of the root port (which is forwarding) and a set of blocked ports except for self-looping ports). The uplink group provides an alternate path in case the currently forwarding link fails.
Switches are normally connected hierarchically, as shown in Figure 4-11. In simpler networks, the upper two levels of the hierarchy may be collapsed into a single backbone layer. Figure 4-11 shows the network topology after spanning tree has converged into a loop-free topology. Spanning tree has blocked the redundant links to avoid loops. Every access switch and distribution switch in Figure 4-11 has a redundant uplink. If the switches begin using the alternate path as soon as they detect a link-down condition on the currently active link, cutover occurs immediately without going through the usual spanning-tree port states; that is, ports transition to the forwarding state immediately without going through the listening and learning states.
To achieve load balancing between redundant links, you can modify the path cost of the uplink ports on a per-VLAN basis using the set spantree portvlancost command. To determine the root path cost for a switch through a particular port, the path cost of the port is added to the root path cost defined in the configuration BPDU. You can also achieve load balancing by designating different backbone switches as the root switch for different VLANs.
Use the set spantree root command to configure a switch as the root switch. When a switch is selected to become the primary root, the default bridge priority is modified so that it becomes the root for the specified VLANs. The bridge priority is first set to 8192. If this does not result in the switch becoming a root, the bridge priority is then modified to be 100 less than that of the current root switch. Since different VLANs could potentially have different root switches, the bridge VLAN priority chosen is one which will make this switch the root for all the VLANs specified. If reducing the bridge priority as low as 1 still does not make the switch become the root switch, the system displays a message.
The set spantree root command reduces the bridge priority (the value associated with the switch) from the default (32,768) to a significantly lower value, which allows the switch to become the root switch. The following example shows how to specify a Catalyst 5000 series switch as the primary root switch for VLANs 1-10:
Console> (enable) set spantree root 1-10 dia 4 VLANs 1-10 bridge priority set to 8192 VLANs 1-10 bridge max aging time set to 14 seconds. VLANs 1-10 bridge hello time set to 2 seconds. VLANs 1-10 bridge forward delay set to 9 seconds. Switch is now the root switch for active VLANs 1-6. Console> (enable)
Use the set spantree root secondary command to configure a switch as the secondary root switch. This command reduces the bridge priority to 16,384, making it the probable candidate to become the root switch if the primary root switch fails. You can run this command on more than one switch to create multiple backup switches in case the primary root switch fails. The following example shows how to specify a Catalyst 5000 series switch as the secondary root switch for VLANs 22 and 24:
Console> (enable) set spantree root secondary 22,24 dia 5 hello 1 VLANs 22,24 bridge priority set to 16384. VLANs 22,24 bridge max aging time set to 10 seconds. VLANs 22,24 bridge hello time set to 1 second. VLANs 22,24 bridge forward delay set to 7 seconds. Console> (enable)
Use the set spantree uplinkfast command to enable and disable the Fast Uplink Switchover feature. This command increases the path cost of all ports on the switch, making it unlikely that the switch would become the root switch. The station_update_rate value represents the number of multicast packets transmitted per 100 milliseconds (the default is 15 packets per millisecond). The following example shows how to enable and verify the Fast Uplink Switchover feature with a station-update rate of 40 packets per 100 milliseconds:
Console> (enable) set spantree uplinkfast enable rate 40 VLANs 1-1000 bridge priority set to 49152. The port cost and portvlancost of all ports increased by 3000. Station update rate set to 40 packets/100ms. uplinkfast turned on for bridge. Console> (enable) Console> (enable) show spantree uplinkfast VLAN port list ------------------------------------------------ 1-20 1/1(fwd),1/2-1/5 21-50 1/9(fwd), 1/6-1/8, 1/10-1/12
Use the set spantree portvlancost command to assign a lower cost to a set of VLANs on a port. If you do not specify the VLANs, the command acts on the VLANs specified in prior instances of this command. If you do not specify a cost, the portvlancost value is set to one less than the current portcost value for the port. The following example shows how to assign a lower cost to a set of VLANs on a port:
Console> (enable) set spantree portvlancost 2/10 1-20 Port 2/10 VLANs 1-20 have a path cost of 9.
For complete descriptions of the commands used to configure the Spanning-Tree Fast Uplink Switchover feature, see the Catalyst 5000 Series Command Reference publication.
The Catalyst 5000 series switch allows you to group end stations with a common set of requirements into logical LAN segments called virtual LANs (VLANs). For example, several end stations in different physical locations attached to different switches can be grouped as a department, such as engineering or accounting. If the end stations are located near one another, they can be grouped into a LAN segment. If any of the end stations are on a different LAN segment, which is typically located in a different building or location, they can be grouped into a VLAN.
For more information about configuring VLANs, refer to "Configuring VLANs."
Fast EtherChannel provides parallel bandwidth of up to 800 Mbps (full duplex) between a Catalyst 5000 series switch and another switch or host by grouping multiple Fast Ethernet interfaces into a single logical transmission path.
Fast EtherChannel segments must be contiguous ports on a Fast Ethernet switching module. You can configure Fast Ethernet ports into Fast EtherChannel groups containing two or four segments, yielding 400- or 800-Mbps bidirectional bandwidth, respectively.
Inbound broadcast and multicast packets on one segment in a channel are blocked from returning on any other segment of the channel. Outbound broadcast and multicast packets are sent through only one channel segment.
If a segment within a channel fails, traffic previously carried over the failed link switches to the remaining segments within the channel. A trap is sent upon a failure identifying the switch, the channel, and the failed link.
Channels are configured using the standard CLI or Simple Network Management Protocol (SNMP).
Catalyst 5000 series software release 3.1 includes an enhancement to the Fast EtherChannel feature called the Port Aggregation Protocol (PAgP). PAgP facilitates the automatic creation of Fast EtherChannel links by sending packets between Fast EtherChannel-capable ports. The protocol learns and informs the neighbors and their group capabilities dynamically. Once PAgP identifies correctly paired Fast EtherChannel links, it groups the ports into a channel. The channel is then added to the spanning tree as a single bridge port.
PAgP includes four user-configurable channel modes: on, off, auto, and desirable. Each mode affects the way a port handles PAgP packets. By default, ports are in auto mode. Table 4-2 describes each of the four modes.
| Mode | Description |
|---|---|
| On | Forces the port to channel without negotiation. |
| Off | Prevents the port from channeling without negotiation. |
| Auto | Places a port into a passive negotiating state, in which the port will respond to PAgP packets it receives but will not initiate PAgP packet negotiation. (Default) |
| Desirable | Places a port into an active negotiating state, in which the port initiates negotiations with other ports by sending PAgP packets. |
Both the auto and desirable modes allow ports to negotiate with connected ports to determine if they can form a channel, based on criteria such as port speed, trunking state, VLAN numbers, and so on.
Channel ports can be in different channel modes as long as the modes are compatible. For instance, a port in desirable mode can form a channel successfully with another port that is in desirable, or auto mode. Similarly, a port in auto mode can form a channel with another port in desirable mode. However, a port in auto mode cannot form a channel with another port that is also in auto mode, since neither port will initiate the needed negotiations.
If improperly configured, some Fast EtherChannel ports will be disabled automatically to avoid network loops and other problems. Use the following guidelines to avoid configuration problems:
Use the set port channel port_list {on | off | auto | desirable} command to configure Fast EtherChannel.
To configure an Ethernet channel, perform the following steps:
| Task | Command |
|---|---|
| Step 1 Make sure that the ports you want to channel are configured correctly. (Refer to the Fast EtherChannel Configuration Guidelines earlier in this chapter.) | None |
| Step 2 Ensure a loop-free topology for all channeled VLANs. | None |
| Step 3 Create an Ethernet channel. | set port channel port_list on |
To set a channel port to auto mode, perform this task:
| Task | Command |
|---|---|
| Set a channel port to auto mode. | set port channel port_list auto |
To set a channel port to desirable mode, perform this task:
| Task | Command |
|---|---|
| Set a channel port to desirable mode. | set port channel port_list desirable |
To remove an Ethernet channel, perform this task:
| Task | Command |
|---|---|
| Remove an Ethernet channel. | set port channel port_list off |
This example shows how to enable Fast EtherChannel on ports 5-8 of Fast Ethernet module 2:
Console> (enable) set port channel 2/5-8 on Port(s) 2/5-8 channel mode set of on. Console> (enable)
To verify that Fast EtherChannel is configured correctly, enter the show port channel [mod_num[port_num]] command. After entering the command, you see this display:
Console> show port channel 4
Port Status Channel Channel Neighbor Neighbor
mode status device port
----- ---------- --------- ----------- ------------------------- ----------
4/1 connected desirable channel WS-C5000 012345678 5/5
4/2 connected desirable channel WS-C5000 012345678 5/6
----- ---------- --------- ----------- ------------------------- ----------
4/3 connected off not channel
4/4 connected off not channel
4/5 notconnect off not channel
4/6 notconnect off not channel
4/7 notconnect off not channel
4/8 notconnect off not channel
----- ---------- --------- ----------- ------------------------- ----------
4/9 connected on channel WS-C5000 987654321 3/1
4/10 connected on channel WS-C5000 987654321 3/2
4/11 notconnect on channel
4/12 connected on channel WS-C5000 987654321 3/4
----- ---------- --------- ----------- ------------------------- ----------
Console>
When using the channel as a trunk, follow these guidelines:
The two-port supervisor engine modules that support Fast EtherChannel (model numbers WS-X5505, WS-X5506, WS-X5509, and WS-X5530) on Catalyst 5000 series switches support a single configuration: one channel of two ports.
The 12-port 10/100BaseTX Fast EtherChannel Switching Module (model number WS-X5203) and the 12-port 100BaseFX Fast EtherChannel Switching Module (model number WS-X5201) support a number of configurations.
The 12 ports on these modules form three groups of four ports each (ports 1-4, 5-8, and 9-12). A Fast EtherChannel must be composed of contiguous ports from the same group. A channel cannot have some ports from one group and some ports from another. Each group of four ports can be channeled in any the following ways:
The Catalyst 5000 series switch increases network throughput by supporting simultaneous, parallel conversations between Ethernet segments. Switched connections between Ethernet segments last only for the duration of the packet. New connections can be made between different segments for the next packet.
The Catalyst 5000 series switch solves congestion problems caused by high bandwidth devices and a large number of users by assigning each of the devices, for example, servers, to its own 10- or 100-Mbps segment. Because each Ethernet port on the Catalyst 5000 series switch represents a separate Ethernet segment, servers in a properly configured switched environment achieve full access to the bandwidth.
Because the major bottleneck in Ethernet networks is usually due to collisions on devices, an effective solution is full-duplex communication, an option for each port on the Catalyst 5000 series switch. Normally, Ethernet operates in half-duplex communication mode, which means that stations can either receive or transmit. In full-duplex mode, two communicating stations can transmit and receive at the same time. When packets can flow in both directions simultaneously, effective Ethernet bandwidth doubles from 10 Mbps to 20 Mbps for 10BaseT ports and to 200 Mbps for Fast Ethernet ports.
Each Ethernet port on the Catalyst 5000 series switch can connect to a single workstation or server, or to a hub through which workstations or servers connect to the network.
Ports on a typical Ethernet hub are all connected to a common backplane within the hub, and the bandwidth of the network is shared by all devices attached to the hub. If two stations establish a session that uses a significant level of bandwidth, the network performance of all other stations attached to the hub is degraded.
To reduce degradation, the Catalyst 5000 series switch treats each port as an individual segment and when stations on different ports need to communicate, switches frames from one port to the other at wire speed. Switching ensures that each session receives the full 10-Mbps bandwidth.
To switch frames between ports efficiently, the Catalyst 5000 series switch maintains an address table. When a frame enters the Catalyst 5000 series switch, it associates the MAC address of the sending station with the port on which it was received.
The Catalyst 5000 series switch builds the address table by using the source address of the frames received. When the switch receives a frame for a destination address not yet listed in its address table, it floods the frame to all ports of the same VLAN except the port that received the frame. When the destination station replies, the switch adds its relevant source address and port ID to the address table. The Catalyst 5000 series switch then forwards subsequent frames to a single port without flooding to all ports.
The address table can store at least 16,000 address entries without flooding any entries. The Catalyst 5000 series switch uses an aging mechanism, defined by a configurable aging timer, so that, if an address remains inactive for a specified number of seconds, it is removed from the address table.
Figure 4-12 shows an example Ethernet configuration for a single Catalyst 5000 series switch. For simplicity, this example shows all devices on each module as either full duplex or half duplex. However, you can configure each port on each module independently for either full- or half-duplex operation. This example also shows a direct correlation between port speed and traffic priority, although the two parameters are completely independent.
The example configuration shown in Figure 4-12 is based on the following assumptions:
Step 1 Configure a name for the port by entering the set port name command. You see this display:
Step 2 Configure the priority level for the port by entering the set port level command. You see this display:
Step 3 Configure a name for the port by entering the port speed command. You see this display:
Step 4 Configure the transmission type of the port (half or full duplex) by entering the set port duplex command. You see this display:
To verify the Ethernet configuration, enter the show port command. After entering this command, you see a display similar to the verification example in the section "Setting the Port Name."
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