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This chapter describes how to configure Gigabit Ethernet switching on the Catalyst enterprise LAN switches. The configuration tasks in this chapter apply to Gigabit Ethernet switch ports on switching modules and fixed-configuration switches, as well as to supervisor engine Gigabit Ethernet uplink ports.
This chapter consists of these sections:
These sections describe how Gigabit Ethernet works:
All Gigabit Ethernet ports can respond to flow-control frames (pause frames) received from neighboring devices by inhibiting the transmission of packets from each port for a period of time. When a pause frame is received on a port, it is processed internally; pause frames are not switched through the system.
Except for ports on the Gigabit EtherChannel module (WS-X5410), Gigabit Ethernet ports on the Catalyst 5000 and 2926G series switches can transmit pause frames to neighboring devices. If the receive buffer for a port becomes full, the module transmits a pause frame on that port that tells remote devices to delay sending more packets for a specified period of time.
Use the set port flow control command to configure flow control on Gigabit Ethernet ports. Table 6-1 describes the flow-control behavior of a Gigabit Ethernet port depending on the set port flowcontrol command keywords used to configure the port.
| Keywords | Gigabit Ethernet Ports | Gigabit EtherChannel Ports1 |
|---|---|---|
receive on | The port uses flow control dictated by the neighbor port. | The port operates with an attached device that is required to send flow-control frames, or with an attached device that is not required to but might send flow-control frames. |
receive desired | The port uses flow control if the neighbor port uses it, and does not use flow control if the neighbor port does not use it. | The port operates with an attached device that is required to send flow-control frames, or with an attached device that is not required to but might send flow-control frames. |
receive off | The port does not use flow control, regardless of whether flow control is requested by the neighbor port. | The port discards received flow-control frames without processing them. If negotiation is enabled, the port advertises that it refuses to accept flow-control frames. This can cause the remote device not to send flow-control frames, or if the attached device is configured to send flow-control frames unconditionally, it can prevent the link from coming up. |
send on | The port sends flow-control frames to the neighbor port. | The local port advertises that it will send flow-control frames. |
send desired | The port sends flow-control frames to the neighbor port if the neighbor port asks to use flow control. | The local port advertises that it will send flow-control frames if the attached device elects to receive them. |
send off | The port does not send flow-control frames to the neighbor port. | The local port advertises that it will never send flow-control frames. |
| 1Catalyst 5000 family WS-X5410 module and Catalyst 4000 family and 2948G Gigabit Ethernet ports only. |
 | Caution Unlike autonegotiation with 10/100 Fast Ethernet, Gigabit Ethernet link negotiation does not involve negotiating port speed. You cannot disable link negotiation on Gigabit Ethernet ports using the set port speed command. |
With Gigabit Ethernet ports, link negotiation is used to exchange flow-control parameters, remote fault information, and duplex information (even though Cisco Gigabit Ethernet ports only support full-duplex mode). With Gigabit Ethernet ports, you configure link negotiation using the set port negotiation command. Gigabit Ethernet port negotiation is enabled by default.
The ports on both ends of a Gigabit Ethernet link must have the same setting. The link will not come up if the ports at each end of the link are set inconsistently (link negotiation enabled on one port and disabled on the other). Table 6-2 shows the four possible link negotiation configurations for a Gigabit Ethernet link and the resulting link status for each configuration.
| Link Negotiation State | Link Status | ||
| Near End1 | Far End2 | Near End | Far End |
Off | Off | Up | Up |
On | On | Up | Up |
Off | On | Up | Down |
On | Off | Down | Up |
| 1Near End refers to the local Gigabit EtherChannel module port. 2Far End refers to the remote port at the other end of the Gigabit link. |
These sections describe how the Catalyst 4000 series oversubscribed Gigabit Ethernet modules work:
The Catalyst 4000 series 18-port server switching 1000BaseX Gigabit Ethernet module (WS-X4418-GB) offers two dedicated 1000BaseX (GBIC) Gigabit Ethernet ports and 16 oversubscribed (possibly blocking) 1000BaseX (GBIC) Gigabit Ethernet ports. The module provides a Gigabit Ethernet network backbone connection for multiple servers or high-end workstations.
Ports 1 and 2 on the module are uplink ports with 1-Gbps dedicated bandwidth for each port. These ports are typically used to connect to the network backbone.
The 16 oversubscribed ports (ports 3-18) are divided into four groups of four ports each. Each group of four ports shares 1 Gbps of bandwidth. Therefore, the average bandwidth required by clients and servers connected to ports in the same group of oversubscribed Gigabit ports should not exceed 1 Gbps. Table 6-3 shows how the oversubscribed Gigabit Ethernet ports are grouped.
.
3 5 7 9 | 11 13 15 17 |
4 6 8 10 | 12 14 16 18 |
Each group of four oversubscribed ports has a buffer for incoming frames to allow connected devices to transmit traffic simultaneously. Because the inbound buffer is small, the default (and recommended) flow-control configuration for the oversubscribed ports is receive desired and transmit on.
You can bundle multiple oversubscribed ports into a Gigabit EtherChannel link to connect to channel-capable servers. Bundling multiple oversubscribed ports in the same port group does not necessarily increase the total available bandwidth compared to using a single link. However, it does provide redundancy with quick failover for links to servers and hosts that support the Port Aggregation Protocol (PAgP).
Figure 6-1 shows an example of how the 18-port server switching module (WS-X4418-GB) can connect multiple network servers and high-end workstations to the Gigabit Ethernet network backbone. These configurations are shown:
Table 6-4 shows the Gigabit Ethernet default configuration.
| Feature | Default Value |
|---|---|
Port enable state | All ports are enabled |
Port name | None |
Port priority | Normal |
Duplex mode | Full duplex |
Flow control |
|
Link negotiation | Enabled |
Spanning-Tree Protocol | Enabled for VLAN 1 |
Native VLAN | VLAN 1 |
Spanning-tree port cost | 4 |
Gigabit EtherChannel | Disabled on all Gigabit Ethernet ports (auto mode) |
These sections describe how to configure Gigabit Ethernet switching ports on the Catalyst enterprise LAN switches:
You can assign names to the ports on Gigabit Ethernet modules to facilitate switch administration.
To assign a name to a port, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Assign a name to a port. | set port name mod_num/port_num [name_string] |
Step 2 Verify that the port name is configured. | show port [mod_num[/port_num]] |
This example shows how to set the name for ports 2/1 and 2/2 and how to verify that the port names are configured correctly:
Console> (enable) set port name 2/1 Backbone Connection Port 2/1 name set. Console> (enable) set port name 2/2 Wiring Closet Port 2/2 name set. Console> (enable) show port 2 Port Name Status Vlan Level Duplex Speed Type ----- ------------------ ---------- ---------- ------ ------ ----- ------------ 2/1 Backbone Connectio connected trunk normal full 1000 1000BaseSX 2/2 Wiring Closet notconnect 1 normal full 1000 1000BaseSX <...output truncated...> Last-Time-Cleared -------------------------- Tue Dec 22 1998, 13:42:04 Console> (enable)
You can configure the priority level of each port. When ports request access to the switching bus simultaneously, the switch uses the port priority level to determine the order in which ports are given access.
To set the port priority level, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Configure the priority level for a port. | set port level mod_num/port_num {normal | high} |
Step 2 Verify that the port priority level is configured correctly. | show port [mod_num[/port_num]] |
This example shows how to set the port priority level to high for port 2/1 and verify that the port priority is configured correctly:
Console> (enable) set port level 2/1 high Port 2/1 level set to high. Console> (enable) show port 2/1 Port Name Status Vlan Level Duplex Speed Type ----- ------------------ ---------- ---------- ------ ------ ----- ------------ 2/1 Backbone Connectio connected trunk high full 1000 1000BaseSX <...output truncated...> Last-Time-Cleared -------------------------- Tue Dec 22 1998, 13:42:04 Console> (enable)
To configure flow control on a Gigabit Ethernet port, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Set the flow-control parameters on a Gigabit Ethernet port. | set port flowcontrol {receive | send} mod_num/port_num {off | on | desired} |
Step 2 Verify the flow-control configuration. | show port flowcontrol |
This example shows how to turn transmit and receive flow control on and how to verify the flow-control configuration:
Console> (enable) set port flowcontrol send 2/1 on
Port 2/1 flow control send administration status set to on
(port will send flowcontrol to far end)
Console> (enable) set port flowcontrol receive 2/1 on
Port 2/1 flow control receive administration status set to on
(port will require far end to send flowcontrol)
Console> (enable) show port flowcontrol 2/1
Port Send FlowControl Receive FlowControl RxPause TxPause Unsupported
admin oper admin oper opcodes
----- -------- -------- -------- -------- ------- ------- -----------
2/1 on on on on 0 0 0
Console> (enable)
To enable link negotiation on a Gigabit Ethernet port, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Enable Gigabit Ethernet link negotiation. | set port negotiation mod_num/port_num enable |
Step 2 Verify the link negotiation configuration. | show port negotiation [mod_num/port_num] |
This example shows how to enable port negotiation and verify the configuration:
Console> (enable) set port negotiation 2/1 enable Port 2/1 negotiation enabled Console> (enable) show port negotiation 2/1 Port Link Negotiation ----- ---------------- 2/1 enabled Console> (enable)
To disable link negotiation on a Gigabit Ethernet port, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Disable Gigabit Ethernet link negotiation. | set port negotiation mod_num/port_num disable |
Step 2 Verify the link negotiation configuration. | show port negotiation [mod_num/port_num] |
This example shows how to disable port negotiation and verify the configuration:
Console> (enable) set port negotiation 2/1 disable Port 2/1 negotiation disabled Console> (enable) show port negotiation 2/1 Port Link Negotiation ----- ---------------- 2/1 disabled Console> (enable)
Use the ping and traceroute commands to test connectivity out Gigabit Ethernet ports.
To check connectivity out a port, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Ping a remote host that is located out the port you want to test. | ping [-s] host [packet_size] [packet_count] |
Step 2 Trace the hop-by-hop route of packets from the switch to a remote host located out the port you want to test. | traceroute host |
Step 3 If the host is unresponsive, check the IP address and default gateway configured on the switch. | show interface |
This example shows how to ping a remote host and how to trace the hop-by-hop path of packets through the network using traceroute:
Console> (enable) ping somehost somehost is alive Console> (enable) traceroute somehost traceroute to somehost.company.com (10.1.2.3), 30 hops max, 40 byte packets 1 engineering-1.company.com (173.31.192.206) 2 ms 1 ms 1 ms 2 engineering-2.company.com (173.31.196.204) 2 ms 3 ms 2 ms 3 gateway_a.company.com (173.16.1.201) 6 ms 3 ms 3 ms 4 somehost.company.com (10.1.2.3) 3 ms * 2 ms Console> (enable)
Posted: Fri Oct 1 13:09:41 PDT 1999
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