Interacting With Baby Giants - Cisco Catalyst 4500 series Administration Manual

Chapter 8 Configuring Interfaces
This example shows how to configure the MTU size on Gigabit Ethernet port 1/1:
switch# conf terminal
switch(config)# interface gi1/1
switch(config-if)# mtu 9198
switch(config-if)# end
switch(config)# end
switch# show interface gigabitethernet 1/2
GigabitEthernet1/2 is administratively down, line protocol is down
Hardware is C6k 1000Mb 802.3, address is 0030.9629.9f88 (bia 0030.9629.9f88)
MTU 9216 bytes, BW 1000000 Kbit, DLY 10 usec,
<...Output Truncated...>
switch#

Interacting with Baby Giants

The baby giants feature, introduced in Cisco IOS Release 12.1(12c)EW, uses the global command
system mtu size to set the global baby giant MTU. This feature also allows certain interfaces to support
Ethernet payload size of up to 1552 bytes.
Both the system mtu command and the per-interface mtu command can operate on interfaces that can
support jumbo frames, but the per-interface mtu command takes precedence.
For example, before setting the per-interface MTU for interface gi1/1, you enter the system mtu 1550
command to change the MTU for gi1/1 to 1550 bytes. You enter the per-interface mtu command to
change the MTU for gi1/1 to 9198 bytes. If you change the baby giant MTU to 1540 bytes with the
command system mtu 1540, the MTU for gi1/1 remains unchanged at 9198 bytes.
Configuring the Port Debounce Timer
You can only configure port debounce on 10-Gigabit Ethernet ports.
Note
The port debounce timer suppresses notification of short link-down events. Link-down events that are
shorter than the port debounce timer are not notified to Layer 2 or Layer 3 protocols, decreasing traffic
loss due to network reconfiguration. You can configure the port debounce timer separately on each LAN
port.
Caution Enabling the port debounce timer causes a delay in link down detections, resulting in loss of traffic
during the debouncing period. This situation might affect the convergence and reconvergence of some
Layer 2 and Layer 3 protocols.
To configure the debounce timer on a port, perform this task:
Command
Step 1
Switch(config)# interface tengigabitethernet
slot/port
OL-30933-01
Purpose
Selects the port to configure.
Software Configuration Guide—Release IOS XE 3.6.0E and IOS 15.2(2)E
Configuring Optional Interface Features
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