Example: Configuring IP Directed Broadcast on an EX Series Switch
IP directed broadcast provides a method of sending broadcast packets to hosts on a specified subnet without broadcasting those packets to hosts on the entire network.
This example shows how to enable a subnet to receive IP directed broadcast packets so you can perform backups and other network management tasks remotely:
Requirements
This example uses the following software and hardware components:
- Junos OS Release 9.4 or later for EX Series switches
- One PC
- One EX Series switch
Before you configure IP directed broadcast for a subnet:
- Ensure that the subnet does not have a direct connection to the Internet.
- Configure routed VLAN interfaces (RVIs) for the ingress and egress VLANs on the switch. See Configuring Routed VLAN Interfaces (CLI Procedure) or Configuring VLANs for EX Series Switches (J-Web Procedure).
Overview and Topology
You might want to perform remote administration tasks such as backups and wake-on-LAN (WOL) application tasks to manage groups of clients on a subnet. One way to do this is to send IP directed broadcast packets targeted at the hosts in a particular target subnet.
The network forwards IP directed broadcast packets as if they were unicast packets. When the IP directed broadcast packet is received by a VLAN that is enabled for targeted-broadcast, the switch broadcasts the packet to all the hosts in its subnet.
In this topology (see Figure 1), a host is connected to an interface on an EX Series switch to manage the clients in subnet 10.1.2.1/24. When the switch receives a packet with the broadcast IP address of the target subnet as its destination address, it forwards the packet to the subnet’s Layer 3 interface and broadcasts it to all the hosts within the subnet.
Figure 1: Topology for IP Directed Broadcast
Table 1 shows the settings of the components in this example.
Table 1: Components of the IP Directed Broadcast Topology
| Property | Settings |
|---|---|
Switch hardware | EX Series switch |
Ingress VLAN name | v0 |
Ingress VLAN IP address | 10.1.1.1/24 |
Egress VLAN name | v1 |
Egress VLAN IP address | 10.1.2.1/24 |
Interfaces in VLAN v0 | ge-0/0/3.0 |
Interfaces in VLAN v1 | ge-0/0/0.0 and ge-0/0/1.0 |
Configuration
To configure IP directed broadcast on a subnet to enable remote management of its hosts:
CLI Quick Configuration
To quickly configure the switch to accept IP directed broadcasts targeted at subnet 10.1.2.1/24, copy the following commands and paste them into the switch’s terminal window:
[edit] set interfaces ge-0/0/0.0
family ethernet-switching vlan members v1
set interfaces ge-0/0/1.0
family ethernet-switching vlan members v1
set interfaces vlan.1
family inet address 10.1.2.1/24 set interfaces ge-0/0/3.0
family ethernet-switching vlan members v0
set interfaces vlan.0
family inet address 10.1.1.1/24 set vlans v1 l3-interface
vlan.1 set vlans v0 l3-interface
vlan.0 set interfaces vlan.1
family inet targeted-broadcast Step-by-Step Procedure
To configure the switch to accept IP directed broadcasts targeted at subnet 10.1.2.1/24:
- Add logical interface ge-0/0/0.0 to VLAN v1:
[edit interfaces]
user@switch# set ge-0/0/0.0 family ethernet-switching vlan members v1 - Add logical interface ge-0/0/1.0 to VLAN v1:
[edit interfaces]
user@switch# set ge-0/0/1.0 family ethernet-switching vlan members v1 - Configure the IP address for the egress VLAN, v1:
[edit interfaces]
user@switch# set vlan.1 family inet address 10.1.2.1/24 - Add logical interface ge-0/0/3.0 to VLAN v0:
[edit interfaces]
user@switch# set ge-0/0/3.0 family ethernet-switching vlan members v0 - Configure the IP address for the ingress VLAN:
[edit interfaces]
user@switch# set vlan.0 family inet address 10.1.1.1/24 - To route traffic between the ingress and egress
VLANs, associate a Layer 3 interface with each VLAN:
[edit vlans]
user@switch# set v1 l3-interface (VLANs)vlan.1
user@switch# set v0 l3–interface vlan.0 - Enable the Layer 3 interface for the egress VLAN
to receive IP directed broadcasts:
[edit interfaces]
user@switch# set vlan.1 family inet targeted-broadcast
Results
Check the results:
