Brocade FastIron Ethernet Switch Layer 3 Routing Configuration Guide - Manual (Page 53)

The commands in this example configure loopback interface 2, assign IP address 10.0.0.2/24 to the
interface, then designate the interface as the source for all SSH packets from the Layer 3 switch.
Syntax: no ip ssh source-interface ethernet { [slotnum/]portnum | loopback num | venum }
The slotnum parameter is required on chassis devices.
The portnum parameter is a valid port number.
The num parameter is a loopback interface or virtual interface number.
SNMP packets
To specify a loopback interface as the SNMP single source trap, enter commands such as the following.
device(config)# interface loopback 1
device(config-lbif-1)# ip address 10.0.0.1/24
device(config-lbif-1)# exit
device(config)# snmp-server trap-source loopback 1
The commands in this example configure loopback interface 1, assign IP address 10.00.1/24 to the
loopback interface, then designate the interface as the SNMP trap source for this device. Regardless of
the port the Brocade device uses to send traps to the receiver, the traps always arrive from the same
source IP address.
Syntax: no snmp-server trap-source ethernet { [slotnum/]portnum | loopback num | venum }
The slotnum variable is required on chassis devices.
The portnum variable is a valid port number.
The num variable is a loopback interface or virtual interface number.
ARP parameter configuration
Address Resolution Protocol (ARP) is a standard IP protocol that enables an IP Layer 3 switch to obtain
the MAC address of another device interface when the Layer 3 switch knows the IP address of the
interface. ARP is enabled by default and cannot be disabled.
NOTE
Brocade Layer 2 switches also support ARP. However, the configuration options described later in this
section apply only to Layer 3 switches, not to Layer 2 switches.
How ARP works
A Layer 3 switch needs to know a destination MAC address when forwarding traffic, because the Layer
3 switch encapsulates the IP packet in a Layer 2 packet (MAC layer packet) and sends the Layer 2
packet to a MAC interface on a device directly attached to the Layer 3 switch. The device can be the
packet final destination or the next-hop router toward the destination.
The Layer 3 switch encapsulates IP packets in Layer 2 packets regardless of whether the ultimate
destination is locally attached or is multiple router hops away. Since the Layer 3 switch IP route table
and IP forwarding cache contain IP address information but not MAC address information, the Layer 3
switch cannot forward IP packets based solely on the information in the route table or forwarding cache.
The Layer 3 switch needs to know the MAC address that corresponds with the IP address of either the
packet locally attached destination or the next-hop router that leads to the destination.
For example, to forward a packet whose destination is multiple router hops away, the Layer 3 switch
must send the packet to the next-hop router toward its destination, or to a default route or default
ARP parameter configuration
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