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UDP Helper with No Configured Broadcast Addresses
• If the incoming packet has a broadcast destination IP address, then the unaltered packet is routed to all
Layer 3 interfaces.
• If the Incoming packet has a destination IP address that matches the subnet broadcast address of any
interface, then the unaltered packet is routed to the matching interfaces.
Troubleshooting UDP Helper
Display debugging information using the command debug ip udp-helper, as shown in Figure 21-17.
Figure 21-17. Debugging UDP Broadcast
Use the command debug ip dhcp when using the IP helper and UDP helper on the same interface, as shown
in Figure 21-18.
Figure 21-18. Debugging IP Helper with UDP Helper
FTOS(conf)# debug ip udp-helper
01:20:22: Pkt rcvd on Gi 5/0 with IP DA (0xffffffff) will be sent on Gi 5/1 Gi 5/2 Vlan 3
01:44:54: Pkt rcvd on Gi 7/0 is handed over for DHCP processing.
Packet 0.0.0.0:68 -> 255.255.255.255:67 TTL 128
2005-11-05 11:59:35 %RELAY-I-PACKET, BOOTP REQUEST (Unicast) received at interface
172.21.50.193 BOOTP Request, XID = 0x9265f901, secs = 0 hwaddr = 00:02:2D:8D:46:DC, giaddr =
0.0.0.0, hops = 2
2005-11-05 11:59:35 %RELAY-I-BOOTREQUEST, Forwarded BOOTREQUEST for 00:02:2D:8D:46:DC to
137.138.17.6
2005-11-05 11:59:36 %RELAY-I-PACKET, BOOTP REPLY (Unicast) received at interface
194.12.129.98 BOOTP Reply, XID = 0x9265f901, secs = 0 hwaddr = 00:02:2D:8D:46:DC, giaddr =
172.21.50.193, hops = 2
2005-07-05 11:59:36 %RELAY-I-BOOTREPLY, Forwarded BOOTREPLY for 00:02:2D:8D:46:DC to
128.141.128.90 Packet 0.0.0.0:68 -> 255.255.255.255:67 TTL 128