Testing DHCP Relay
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02-22-2013 02:22 PM - edited 03-04-2019 07:07 PM
We are constantly having DHCP problems on our network. The problem is not with the network tranports, it's with the system admins who maintains the DHCP server (scopes). Is there a way that I can stimulate a DHCP relay on a network to a remote dhcp server using an ip helper address?
I would then enable dhcp debugging to view the transaction. The debugging is simple, but I need to figure a way to test dhcp relay. Any solution would be appreciated so that I can tell the sysadmin its not the network, but the server.
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Routing Protocols
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02-22-2013 03:04 PM
Cisco IOS support dhcp relay agent.
You can configure ip helper-address on an interface or vlan.
Please find below Cisco Documentation that might help you.
http://www.cisco.com/en/US/docs/ios/12_4t/ip_addr/configuration/guide/htdhcpre.html
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02-22-2013 06:00 PM
Yes you can, and then the dhcp packet ( originating from the dhcp client) will be forwarded as unicast by the relay with a new define "giaddr ip" which is usually set to the svi interface on where you have applied this relay,
res
Paul
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Kind Regards
Paul
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02-22-2013 06:19 PM
Sorry, let me rephrase my question. How do I fake a client on my router or layer 3 switch?
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02-23-2013 02:24 AM
Hello David,
if you want a different router to act as a DHCP client you can use
ip address dhcp
in interface config mode
But it has to be a different router /router interface then the one performing DHCP relay function
Hope to help
Giuseppe

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02-23-2013 06:21 AM
You could look into configuring a IP SLA on the ciao for DHCP this will not solve the problem but it give you a better look at the process from the routers perspective and provide better logging from the network perspective.
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