Protocol
UDP port number
TACACS (Terminal Access Controller Access Control System)
49
TFTP (Trivial File Transfer Protocol)
69
Time Service
37
Configuring UDP Helper
Follow these
configure UDP Hel
steps to
per:
To do…
Use the command…
Remarks
Enter system view
system-view
—
Enable UDP Helper
udp-helper enable
y default.
Required
Disabled b
Specify a UDP port number
|
tbios-ns
|
tacacs
|
tftp
|
time
}
y
of the six port numbers 53, 138,
9 and 37.
udp-helper port
{
port-number
dns
|
netbios-ds
|
ne
Optional
By default, the device enabled with
UDP Helper forwards the
broadcast packets containing an
137, 49, 6
Enable the UDP Helper TTL-keep
function
udp
-
helper ttl-keep enable
per does not forward IP
broadcasts with the TTL field being
Optional
Disabled by default. That is, UDP
Hel
1.
Enter VLAN interface view
interface Vlan-interface vlan-id
—
Specify the
which the UDP
destination server to
packets are to be
forwarded
udp-helper server
ip-address
n server is specified
by default.
Required
No destinatio
z
P helper function is disabled, all configured UDP
z
cify the same port.
z
belonging to the VLAN and having a matching UDP port will be unicast
to the destination server.
You need to enable UDP Helper before specifying any UDP port to match UDP broadcasts;
otherwise, the configuration fails. When the UD
ports are disabled, including the default ports.
The
dns
,
netbios-ds
,
netbios-ns
,
tacacs
,
tftp
, and
time
keywords correspond to the six default
ports. You can configure the default ports by specifying port numbers or the corresponding
parameters. For example,
udp-helper port
53 and
udp-helper port
dns
spe
z
You can specify up to 20 destination server addresses on a VLAN interface.
If UDP Helper is enabled after a destination server is configured for a VLAN interface, the
broadcasts from interfaces
51-2