host-identifier and option 82

[Simon Hobson]

Michal Vanão wrote:

>The only problem I've seen so far is that the 
>client fails to renew its IP after T1 passes 
>(because RENEWING DHCPREQUEST is sent directly 
>to server bypassing agent relay). If I 
>understand the RFC correctly, client should 
>"succeed" in REBIND (after T2 passes) because 
>REBINDING DHCPREQUEST is broadcasted hence seen 
>by relay agent. Relay agent shall add opt 82 
>into DHCPREQUEST in this stage. With properly 
>inserted opt 82, server should be able to match 
>static host decl again.
>
>Is this the way it is supposed to work?

I suspect it's one of those "grey areas" ! If a 
relay agent only adds Option 82 to packets it 
picks up through "normal" operation, then what 
you've observed is correct.

While it's not something I've used myself, from 
comments on this list I get the impression that 
some equipment will snoop traffic and still add 
Option 82 to non-broadcast DHCP packets. That 
does of course require that the relay agent is in 
the same path as the normal unicast packets - ie 
a unicast DHCP packet will pass through the same 
interface, and thus get the same Option 82 value 
as it would if broadcast.

-- 
Simon Hobson

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