A network engineer is configuring a routed interface to forward broadcasts of UDP 69, 53, and 49 to 172.20.14.225.
Which command should be applied to the configuration to allow this?
A . router(config-if)#ip helper-address 172.20.14.225
B . router(config-if)#udp helper-address 172.20.14.225
C . router(config-if)#ip udp helper-address 172.20.14.225
D . router(config-if)#ip helper-address 172.20.14.225 69 53 49
Answer: A
Explanation:
To let a router forward broadcast packet the command ip helper-address can be used. The broadcasts will be forwarded to the unicast address which is specified with the ip helper command.
ip helper-address {ip address}
When configuring the ip helper-address command, the following broadcast packets will be forwarded by the router by default:
TFTP ― UDP port 69
Domain Name System (DNS) C UDP port 53
Time service ― port 37
NetBIOS Name Server ― port 137
NetBIOS Datagram Server ― port 138
Bootstrap Protocol (BOOTP) ― port 67
TACACS C UDP port 49
Reference: http://www.cisco-faq.com/163/forward_udp_broadcas.html