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3. Troubleshooting Functional Failures in Operation
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2. Execute the show ip route command to check the route information acquired by this system.
3. Go to "3.7 IPv4 Unicast Routing Communication Failure" if the route information on the failed interface is missing
in the route information acquired by this system or if the next hop address is invalid.
4. If the route information acquired by this system contains the route information on the failed interface, the following
functions set for the interface may have problem. Check these functions.
• Filtering/QoS function
Go to "(f)Checking filtering/QoS setting information."
• DHCP/BOOTP function
Go to "(g)Checking DHCP/BOOTP setting information."
(f) Checking filtering/QoS setting information
It may have been set to discard only certain packets by filtering, or packets may have been discarded through
bandwidth monitoring, discarding control, or shaper of the QoS control.
Check to see if the conditions of filtering and QoS control in the configuration have been set up correctly and if
bandwidth monitoring, discarding control, or shaper has been set up appropriately for system operation. For the
procedure, see "3.23.1 Checking Filtering/QoS Setting Information."
(g) Checking DHCP/BOOTP setting information
If there are sufficient lease IP addresses remaining in the DHCP/BOOTP server, IP addresses may not be assigned to
clients due to configuration setting errors for the DHCP/BOOTP relay. The followings are the steps to check the
configuration:
1. Confirm that the IP address of the DHCP/BOOTP server or that of a neighboring router with the DHCP/BOOTP
relay agent function has been assigned for ip helper-address.
2. Confirm that ip helper-address has been assigned for the client interface.
3. Confirm that ip bootp-hops is set to a correct "bootp hops" value for the client.
4. For multi-homed configuration, confirm that the "ip relay-agent-address" value matches the IP address subnet
distributed by the DHCP/BOOTP server.
(h) Checking when the DCCP relay and VRRP are operated on the same interface
If the DHCP/BOOTP relay and VRRP are operated on the same interface, the DHCP/BOOTP client gateway address
(router option) must be set to the virtual router address specified in the VRRP configuration on the DHCP/BOOTP
server. Otherwise, communication of the DHCP/BOOTP client may be disabled after master/standby router switching
by VRRP. Follow the checking method for each DHCP/BOOTP server.
(2) DHCP server communication trouble
The following are three possible causes for DHCP server communication failures (address not distributed to clients).
1. Configuration error
2. Network configuration has changed
3. DHCP server failure
First, check 1 above. This section describes configurations that are easily misconfigured. For 2 above, check for the
differences in the network configuration provided before and after the change. Check for any difference disabling
communication. If the configuration and network configuration are correct but IP communications are unavailable
because IP addresses cannot be assigned to clients, described in 3 above, see "(b)Checking the log message and
interface" through "(e)Checking filtering/QoS setting information" for details.
To locate the failed part and cause, follow the flow below.