Chapter 5 Troubleshooting Bootp/Dhcp/Udp Relay; Use A Network Diagram; Use The Osi Model To Guide Your Troubleshooting; Udp Relay Configuration Problems - Alcatel OmniSwitch 6624 Troubleshooting Manual

Starting the Troubleshooting Procedure

Use a Network Diagram

It is extremely important to know where the server is in relation to the client, which switch both the client
and the server is directly connected to and their port numbers. A network diagram presents this kind of
information, for example, in an easily understood matter.
Switch VLAN IP Addresses:
10.10.10.200
20.20.20.200
Sample Diagram Showing the Relay Point, Client, and Server

Use the OSI Model to Guide Your Troubleshooting

Note that bridging cannot work unless the physical layer is working. The same is true for all layers above
the physical. Start with this layer first then work your way up through the other layers.

UDP Relay Configuration Problems

Incorrect Server IP Address

Specifying the incorrect IP address for the server is a simple and common mistake that causes UDP relay
to fail. The show ip helper CLI command lists the IP address (s) of all DHCP servers. This is the most
useful command to determine if the IP address for the server is correct.
The following is a sample of the show ip helper CLI command:
-> show ip helper
Ip helper :
Forward Delay(seconds) = 3,
Max number of hops
Forward option
Forwarding Address :
10.10.10.58
Note that if the forward option is set to any thing other than standard, there will be restrictions as to which
UDP frames will be forwarded via the UDP relay function. the "DHCP Relay" chapter from the appropri-
ate OmniSwitch Network Configuration Guide.
page 5-2
VLAN 10
Client
VLAN 20
= 4,
= standard
Troubleshooting BOOTP/DHCP/UDP Relay
DHCP Server
IP Address: 10.10.10.58
OmniSwitch 7800
Client
OmniSwitch Troubleshooting Guide September 2005