Service Manual
UDP Helper with Subnet Broadcast Addresses
When the destination IP address of an incoming packet matches the subnet broadcast address of any interface, the system changes
the address to the congured broadcast address and sends it to matching interface.
In the following illustration, Packet 1 has the destination IP address 1.1.1.255, which matches the subnet broadcast address of VLAN
101. If you congured UDP helper and the packet matches the specied UDP port, the system changes the address to the
congured IP broadcast address and oods the packet on VLAN 101.
Packet 2 is sent from the host on VLAN 101. It has a broadcast MAC address and a destination IP address of 1.1.1.255. In this case, it
is ooded on VLAN 101 in its original condition as the forwarding process is Layer 2.
Figure 44. UDP Helper with Subnet Broadcast Addresses
UDP Helper with Congured Broadcast Addresses
Incoming packets with a destination IP address matching the congured broadcast address of any interface are forwarded to the
matching interfaces.
In the following illustration, Packet 1 has a destination IP address that matches the congured broadcast address of VLAN 100 and
101. If you enabled UDP helper and the UDP port number matches, the packet is ooded on both VLANs with an unchanged
destination address.
Packet 2 is sent from a host on VLAN 101. It has broadcast MAC address and a destination IP address that matches the congured
broadcast address on VLAN 101. In this case, Packet 2 is ooded on VLAN 101 with the destination address unchanged because the
forwarding process is Layer 2. If you enabled UDP helper, the packet is ooded on VLAN 100 as well.
Figure 45. UDP Helper with Congured Broadcast Addresses
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IPv4 Routing