Brocade Communications Systems Layer 3 Routing Configuration ICX 6650 - Manual (Page 53)

Brocade ICX 6650 Layer 3 Routing Configuration Guide 35
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Configuring IP parameters – Layer 3 Switches
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 stack-unit/slotnum/portnum | loopback num | ve
num | management num
The num variable is a loopback interface, virtual interface or management interface number.
SNMP packets
To specify a loopback interface as the SNMP single source trap, enter commands such as the
following.
Brocade(config)# interface loopback 1
Brocade(config-lbif-1)# ip address 10.0.0.1/24
Brocade(config-lbif-1)# exit
Brocade(config)# snmp-server trap-source loopback 1
The commands in this example configure loopback interface 1, assign IP address 10.0.0.1/24 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 stack-unit/slotnum/portnum | loopback num | ve
num
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. The description in “How ARP works” also applies to ARP
on Brocade Layer 2 Switches. 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.