To view the configured broadcast address for an interface, use show interfaces command.Dell#show interfaces vlan 100Vlan 100 is up, line protocol is downAddress is 00:01:e8:0d:b9:7a, Current address is 00:01:e8:0d:b9:7aInterface index is 1107787876Internet address is 1.1.0.1/24IP UDP-Broadcast address is 1.1.255.255MTU 1554 bytes, IP MTU 1500 bytesLineSpeed autoARP type: ARPA, ARP Timeout 04:00:00Last clearing of "show interface" counters 00:07:44Queueing strategy: fifoInput Statistics:0 packets, 0 bytesTime since last interface status change: 00:07:44Configurations Using UDP HelperWhen you enable UDP helper and the destination IP address of an incoming packet is a broadcast address, Dell Networking OS suppressesthe destination address of the packet.The following sections describe various configurations that employ UDP helper to direct broadcasts.• UDP Helper with Broadcast-All Addresses• UDP Helper with Subnet Broadcast Addresses• UDP Helper with Configured Broadcast Addresses• UDP Helper with No Configured Broadcast AddressesUDP Helper with Broadcast-All AddressesWhen the destination IP address of an incoming packet is the IP broadcast address, Dell Networking OS rewrites the address to match theconfigured broadcast address.In the following illustration:1 Packet 1 is dropped at ingress if you did not configure UDP helper address.2 If you enable UDP helper (using the ip udp-helper udp-port command), and the UDP destination port of the packet matchesthe UDP port configured, the system changes the destination address to the configured broadcast 1.1.255.255 and routes the packetto VLANs 100 and 101. If you do not configure an IP broadcast address (using the ip udp-broadcast-address command) onVLANs 100 or 101, the packet is forwarded using the original destination IP address 255.255.255.255.Packet 2, sent from a host on VLAN 101 has a broadcast MAC address and IP address. In this case:1 It is flooded on VLAN 101 without changing the destination address because the forwarding process is Layer 2.2 If you enabled UDP helper, the system changes the destination IP address to the configured broadcast address 1.1.255.255 andforwards the packet to VLAN 100.3 Packet 2 is also forwarded to the ingress interface with an unchanged destination address because it does not have broadcastaddress configured.426 IPv4 Routing
