Strange renew unicast - help needed

[Nikolay P]

----- "Peter Rathlev" <peter at rathlev.dk> wrote:

Peter, thank you for reply.

> That looks like a malformed request. CIADDR is supposed to contain
> the
> clients current IP address. From RFC 2131:
> 
>    : ciaddr  4  Client IP address; only filled in if client is in
>    :            BOUND, RENEW or REBINDING state and can respond
>    :            to ARP requests.
> 
> If on the other hand it was an initial request (i.e. the client has
> no
> valid IP address) then either GIADDR should contian something or the
> client is assumed to connected to the same segment as the server.

Definitely it was not initial request. It was renewal request.
The client and server are connected to different VLANs.


> The server apparently does what it's supposed to cf. RFC 2131 4.1
> regarding destination IP address and MAC address:
> 
>    : [...] If 'giaddr' is zero and 'ciaddr' is zero, and the
>    : broadcast bit is set, then the server broadcasts
>    : DHCPOFFER and DHCPACK messages to 0xffffffff. If the
>    : broadcast bit is not set and 'giaddr' is zero and
>    : 'ciaddr' is zero, then the server unicasts DHCPOFFER
>    : and DHCPACK messages to the client's hardware address
>    : and 'yiaddr' address.  In all cases, when 'giaddr' is
>    : zero, the server broadcasts any DHCPNAK messages to
>    : 0xffffffff.
> 

OK. I am glad the server works as it should.


> Yup. But it's the client that misbehaves. GIADDR is supposed to be
> zeroed out on a regular "renew" request, but CIADDR is supposed to
> contain the currently held IP address.
> 

This is what made me to think there is something wrong. I have never seen this behavior before. This problem occurred after I connected this station via wireless bridge. When this station was connected with cable it operated fine. But cable gone bad and I had to temporarily connect the station with wireless Level 2 bridge. This is the only change I made. Anyway for the station nothing should really change - it has Ethernet connection and wireless stuff should be absolutely transparent to the station. It is connected to the same VLAN as it was before.

I had problem with DHCP snooping after I connected wireless bridge (requests from client would be blocked), so I disabled DHCP snooping entirely.

> 
> Does the client then get the same address again?
>

Yes, it does - I have static DHCP lease assignment for this station, so it will get the same address anyway.

What else I can tell is if I issue 'dhcpcd -n' command it successfully rebinds the address with first attempt (because it broadcasts it)