System information

Troubleshooting Booting Problems
Book Title
3-52
Booting: Undefined Load Module Error When Netbooting
Symptom: An undefined load module error occurs during a netboot. The console display indicates
an “undefined load module” error, and the router is unable to boot.
Table 3-18 outlines the problem that might cause this symptom and describes solutions to that
problem.
Possible Problem Solution
Intermediate routers
have ARP filtering enabled
Step 1 Boot the router from ROM.
Step 2 Make sure you can ping the server from the router.
Step 3 Use the copy running-config tftp privileged exec command to test TFTP
connectivity to the server.
Step 4 If the preceding steps are successful, check the configuration at the
intermediate router using the show arp exec command.
Step 5 Enable the debug arp privileged exec command to determine whether
neighbor proxy ARP responses are being generated.
Caution: Because debugging output is assigned high priority in the CPU
process, it can render the system unusable. For this reason, use debug
commands only to troubleshoot specific problems or during
troubleshooting sessions with Cisco technical support staff. Moreover, it
is best to use debug commands during periods of lower network traffic
and fewer users. Debugging during these periods decreases the likelihood
that increased debug command processing overhead will affect system
use.
Step 6 If the neighbor is not sending proxy ARP responses and its configuration
contains the no ip proxy-arp interface configuration command, disable
ARP filtering by removing the entry.
Note that proxy ARP is enabled by default.
Step 7 If you need to have a no ip proxy-arp entry in the neighbor router
configurations, use the ip default-gateway global configuration
command on the router to specify a default gateway.
Missing or misconfigured IP
helper address on intermediate
router
Step 1 Check the configurations of all routers in the path. Make sure that all
intermediate routers have an IP helper address specified that points to the
TFTP server.
Syntax:
ip helper-address address
Syntax Description:
• address—Destination broadcast or host address to be used when
forwarding UDP
1
broadcasts. You can have more than one helper
address per interface.
Step 2 Include helper addresses as required using the ip helper-address
interface configuration command.
If you are unicasting to your server, you do not need to use the
IP helper address, but if you are broadcasting to 255.255.255.255 (by
omitting the IP address of the server), add the ip helper-address
command on the neighboring router interface used in the netbooting
broadcast.
1 UDP = User Datagram Protocol