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8-6
Troubleshooting
Unusual Network Activity
Troubleshooting
One indication of a duplicate IP address in a DHCP network is this Event Log
message:
ip: Invalid ARP source:
IP address
on
IP address
where: both instances of
IP address
are the same address, indicating the
IP address that has been duplicated somewhere on the network.
The Switch Has Been Configured for DHCP/Bootp Operation, But Has
Not Received a DHCP or Bootp Reply. When the switch is first config-
ured for DHCP/Bootp operation, or if it is rebooted with this configuration, it
immediately begins sending request packets on the network. If the switch does
not receive a reply to its DHCP/Bootp requests, it continues to periodically
send request packets, but with decreasing frequency. Thus, if a DHCP or Bootp
server is not available or accessible to the switch when DHCP/Bootp is first
configured, the switch may not immediately receive the desired configuration.
After verifying that the server has become accessible to the switch, reboot the
switch to re-start the process.
Automatic Broadcast Control Problems
After Enabling ABC, Some Clients in a DHCP Network Using a Router
as a Gateway Cannot Communicate with their Servers or Other
Devices. When ABC is enabled in IP or IP-IPX networks, the default
Auto Gateway parameter is set to Ye s . Generally, this should be used only where
you want client-server traffic to remain in the client’s broadcast domain. In a
DHCP network this causes the switch to intercept DHCP server reply packets,
change the default router option field within the these packets to match the
clients’ IP addresses, then forward the modified reply packets to the clients.
This effectively configures the clients to be their own gateways. In a DHCP
network where a router must serve as a gateway, this causes clients to lose
contact with devices that are reached through the router. Possible solutions
include:
• Disable the Auto Gateway parameter. (See the procedure on page
6-109.)
• On the gateway router, enable Proxy ARP if available.
Note that the Auto Gateway and IP RIP Control are not functional without an
IP address and subnet mask.