Reference Guide

IPv4 Addressing | 473
Figure 24-5. UDP Helper with Configured Broadcast Addresses
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 the following
example.
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.
Use the command debug ip dhcp when using the IP helper and UDP helper on the same interface, as shown
in the following example.
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
P
acket 1
D
estination Address:
1
.1.255.255
1/1
Ingress interface
IP Address: 2.1.1.1/24
UDP helper enabled
1/2
1/3
VLAN 100
IP address: 1.1.0.1/24
Subnet broadcast address: 1.1.0.255
Configured broadcast address: 1.1.255.2
55
Hosts on VLAN 100: 1.1.0.2, 1.1.0.3, 1.1.0.4
VLAN 101
IP address: 1.11.1/24
Subnet broadcast address: 1.1.1.255
Configured broadcast address: 1.1.255.255
Hosts on VLAN 100: 1.1.1.2, 1.1.1.3, 1.1.1.4
fnC0048m
p
Packet 2
Switched Packet
Destination Address:
1.1.255.255