First lets talk about option 82. What is it? It is a DHCP option that was created because of relay-agents (like your router doing an "ip helper-address"). When the relay-agent forwards the DHCP request to the server it includes in that packet option 82 which tells the DHCP server information about the client so it knows what address range it is coming from.
So,what happens is that your L3 switch by default will insert option 82 information. When the router sees that it is not trusted by default and it gets rejected. There are 2 ways to get around this. You can turn off the option 82 insertion on the switch, or you can tell the router to trust the inserted option 82 information. Check out this doc: http://www.cisco.com/en/US/docs/switches/lan/catalyst3550/software/release/12.1_13_ea1/configuration/guide/swdhcp82.html On Wed, Jul 22, 2009 at 4:00 AM, Jowi Nkwe (JM) <[email protected]> wrote: > > Good Day, > > Can someone clarify the problem encountered with switch relaying > information to the DHCP server ( a router) and the server does not > allocate an address due to error message "inconsistent relay > information". The debug also mention something about the giaddr.. > > Secondly what is option 82, with regards to the DHCP errors.? > > Kind Regards, > Jowi > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > This e-mail is subject to the Telkom SA electronic communication legal > notice, available at : > http://www.telkom.co.za/TelkomEMailLegalNotice.PDF > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > _______________________________________________ > For more information regarding industry leading CCIE Lab training, please > visit www.ipexpert.com > -- Regards, Joe Astorino - CCIE #24347 R&S Technical Instructor - IPexpert, Inc. Cell: +1.586.212.6107 Fax: +1.810.454.0130 Mailto: [email protected]
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