Dell POWEREDGE M1000E - Manual (Page 907)

38-15
Cisco Catalyst Blade Switch 3130 and 3032 for Dell Software Configuration Guide
OL-13270-03
Chapter 38 Configuring IP Unicast Routing
Configuring IP Addressing
Configuring Broadcast Packet Handling
After configuring an IP interface address, you can enable routing and configure one or more routing
protocols, or you can configure the way the switch responds to network broadcasts. A broadcast is a data
packet destined for all hosts on a physical network. The switch supports these kinds of broadcasting:
• A directed broadcast packet sent to a specific network or series of networks. A directed broadcast
address includes the network or subnet fields.
• A flooded broadcast packet sent to every network.
Note You can also limit broadcast, unicast, and multicast traffic on Layer 2 interfaces by using the
storm-control interface configuration command to set traffic suppression levels. For more information,
see
Chapter 26, “Configuring Port-Based Traffic Control.”
Routers provide some protection from broadcast storms by limiting the extent to the local cable. Bridges
(including intelligent bridges), because they are Layer 2 devices, forward broadcasts to all network
segments, thus propagating broadcast storms. The best solution to the broadcast storm problem is to use
a single broadcast address scheme on a network. In most IP implementations, you can set the broadcast
address. Many implementations, including the one in the switch, support several addressing schemes for
forwarding broadcast messages.
Perform the tasks in these sections to enable these schemes:
• Enabling Directed Broadcast-to-Physical Broadcast Translation, page 38-15
• Forwarding UDP Broadcast Packets and Protocols, page 38-16
• Establishing an IP Broadcast Address, page 38-17
• Flooding IP Broadcasts, page 38-18
Enabling Directed Broadcast-to-Physical Broadcast Translation
By default, IP directed broadcasts are dropped; they are not forwarded. Dropping IP-directed broadcasts
makes routers less susceptible to denial-of-service attacks.
You can enable forwarding of IP-directed broadcasts on an interface when the broadcast becomes a
physical (MAC-layer) broadcast. Only those protocols configured by using the ip forward-protocol
global configuration command are forwarded.
You can specify an access control list (ACL) to control which broadcasts are forwarded. When an ACL
is specified, only those IP packets permitted by the ACL can be translated from directed broadcasts to
physical broadcasts. For more information on access lists, see
Chapter 34, “Configuring Network
Security with ACLs.”
Beginning in privileged EXEC mode, follow these steps to enable forwarding of IP-directed broadcasts
on an interface:
Command Purpose
Step 1 configure terminal Enter global configuration mode.
Step 2 interface interface-id Enter interface configuration mode, and specify the interface to
configure.