3Com SuperStack II 3300, User Manual

Page: 74 / 172

74 C
HAPTER
8: S
ETTING
IP P
ARAMETERS
Querying Name
Servers
You can check the resolution between IP addresses and host names on a
Name Server. You enter either the host name or the IP address, and the
DNS client displays the pair.
To query a name server:
1 Enter the following at the top-level menu:
ip dns nslookup
The following prompt is displayed:
Enter host information (IP address/name):
2 Enter the host name or an IP address at the prompt.
The module returns the associated host name or IP address.
Administering UDP
Helper
UDP Helper permits the routing of UDP broadcast frames between VLANs
when these broadcasts are not normally routed between VLANs. With
UDP Helper, protocols such as the Bootstrap Protocol (BOOTP) and the
Dynamic Host Configuration Protocol (DHCP) are available so that you
can boot hosts through this router.
The UDP services that are mentioned in this section on UDP Helper use
the following ports:
■
BOOTP and DHCP = 67
■
TIME = 37
■
DNS = 53
UDP Helper allows you to set the number of times a UDP packet is
forwarded between subnetworks. In addition, UDP packets are discarded
based on the hop count and the seconds value for BOOTP and DHCP
packets. The forwarding address that the UDP Helper uses is either the IP
broadcast address, for example, 10.255.255.255, or the IP addresses of
the relevant DHCP, BOOTP, TIME or DNS servers.
Displaying UDP
Helper Information
To display the hop count, threshold configuration and list the ports and
the IP forwarding addresses that are defined for each port, enter the
following at the top-level menu:
ip udpHelper display