Cisco 7604 Configuration Manual page 135

Chapter 9 Configuring Interfaces
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Bridged and Routed Traffic Size Check at Ingress 10, 10/100, and 100 Mbps Ethernet and 10-Gigabit Ethernet Ports
Jumbo frame support compares ingress traffic size with the global LAN port MTU size at ingress 10,
10/100, and 100 Mbps Ethernet and 10-Gigabit Ethernet LAN ports that have a nondefault MTU size
configured. The port drops traffic that is oversized. You can configure the global LAN port MTU size
(see the
Bridged and Routed Traffic Size Check at Ingress Gigabit Ethernet Ports
Gigabit Ethernet LAN ports configured with a nondefault MTU size accept frames containing packets
of any size larger than 64 bytes. With a nondefault MTU size configured, Gigabit Ethernet LAN ports
do not check for oversize ingress frames.
Routed Traffic Size Check on the PFC
For traffic that needs to be routed, Jumbo frame support on the PFC compares traffic sizes to the
configured MTU sizes and provides Layer 3 switching for jumbo traffic between interfaces configured
with MTU sizes large enough to accommodate the traffic. Between interfaces that are not configured
with large enough MTU sizes, if the "do not fragment bit" is not set, the PFC sends the traffic to the
MSFC to be fragmented and routed in software. If the "do not fragment bit" is set, the PFC drops the
traffic.
Bridged and Routed Traffic Size Check at Egress 10, 10/100, and 100 Mbps Ethernet Ports
10, 10/100, and 100 Mbps Ethernet LAN ports configured with a nondefault MTU size transmit frames
containing packets of any size larger than 64 bytes. With a nondefault MTU size configured, 10, 10/100,
and 100 Mbps Ethernet LAN ports do not check for oversize egress frames.
Bridged and Routed Traffic Size Check at Egress Gigabit Ethernet and 10-Gigabit Ethernet Ports
Jumbo frame support compares egress traffic size with the global egress LAN port MTU size at egress
Gigabit Ethernet and 10-Gigabit Ethernet LAN ports that have a nondefault MTU size configured. The
port drops traffic that is oversized. You can configure the global LAN port MTU size (see the
"Configuring the Global Egress LAN Port MTU Size" section on page
Ethernet Ports
These sections describe configuring nondefault MTU sizes on Ethernet ports:
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Ethernet Port Overview
Configuring a nondefault MTU size on a 10, 10/100, or 100 Mbps Ethernet port limits ingress packets
to the global LAN port MTU size and permits egress traffic of any size larger than 64 bytes.
Configuring a nondefault MTU size on a Gigabit Ethernet port permits ingress packets of any size larger
than 64 bytes and limits egress traffic to the global LAN port MTU size.
OL-4266-08
Jumbo frame support fragments routed traffic in software on the MSFC.
Jumbo frame support does not fragment bridged traffic.
"Configuring the Global Egress LAN Port MTU Size" section on page
Ethernet Port Overview, page 9-11
Layer 3 Ethernet Ports, page 9-12
Layer 2 Ethernet Ports, page 9-12
Cisco 7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX
Configuring Optional Interface Features
9-13).
9-13).
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