Configuring Packet Parameters - Dell PowerConnect B-FCXs Configuration Manual

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Configuring IP parameters – Layer 3 Switches
NOTE
In the previousexample, 209.157.22.199 is the IP address of the domain name server (default DNS
gateway address), and 209.157.22.80 represents the IP address of the NYC02 host.

Configuring packet parameters

You can configure the following packet parameters on Layer 3 Switches. These parameters control
how the Layer 3 Switch sends IP packets to other devices on an Ethernet network. The Layer 3
Switch always places IP packets into Ethernet packets to forward them on an Ethernet port.
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Changing the encapsulation type
The Layer 3 Switch encapsulates IP packets into Layer 2 packets, to send the IP packets on the
network. (A Layer 2 packet is also called a MAC layer packet or an Ethernet frame.) The source
address of a Layer 2 packet is the MAC address of the Layer 3 Switch interface sending the packet.
The destination address can be one of the following:
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The entire IP packet, including the source and destination address and other control information
and the data, is placed in the data portion of the Layer 2 packet. Typically, an Ethernet network
uses one of two different formats of Layer 2 packet:
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The control portions of these packets differ slightly. All IP devices on an Ethernet network must use
the same format. Layer 3 Switches use Ethernet II by default. You can change the IP encapsulation
to Ethernet SNAP on individual ports if needed.
NOTE
All devices connected to the Layer 3 Switch port must use the same encapsulation type.
To change the IP encapsulation type on interface 5 to Ethernet SNAP, enter the following
commands.
PowerConnect(config)# interface ethernet 5
PowerConnect(config-if-e1000-5)# ip encapsulation snap
Syntax: ip encapsulation snap | ethernet_ii
806
Encapsulation type – The format for the Layer 2 packets within which the Layer 3 Switch sends
IP packets.
Maximum Transmission Unit (MTU) – The maximum length of IP packet that a Layer 2 packet
can contain. IP packets that are longer than the MTU are fragmented and sent in multiple
Layer 2 packets. You can change the MTU globally or an individual ports:
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Global MTU – The default MTU value depends on the encapsulation type on a port and is
1500 bytes for Ethernet II encapsulation and 1492 bytes for SNAP encapsulation.
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Port MTU – A port default MTU depends on the encapsulation type enabled on the port.
The MAC address of the IP packet destination. In this case, the destination device is directly
connected to the Layer 3 Switch.
The MAC address of the next-hop gateway toward the packet destination.
An Ethernet broadcast address.
Ethernet II
Ethernet SNAP (also called IEEE 802.3)
PowerConnect B-Series FCX Configuration Guide
53-1002266-01