[Dnsmasq-discuss] DHCP Relay, assign address from other vlan, with no dhcp listening on it
Simon Kelley
simon at thekelleys.org.uk
Mon Sep 12 13:09:50 BST 2011
SpiderX wrote:
>> I think what's happening is that the relay adds its 172.... address to
>> the relayed DHCP packet
> Thanks for reply, Simon.
> Are you talking about giaddr field?
That's the one.
>If no, then there is no any other
> 172... in the packet:
> IP: 172.16.33.50 (1c:bd:b9:9b:68:5c) > 172.16.33.252 (0:1e:67:2:ad:6a)
> OP: 1 (BOOTPREQUEST)
> HTYPE: 1 (Ethernet)
> HLEN: 6
> HOPS: 1
> XID: 830b9708
> SECS: 0
> FLAGS: 0
> CIADDR: 0.0.0.0
> YIADDR: 0.0.0.0
> SIADDR: 0.0.0.0
> GIADDR: 172.16.33.50
> CHADDR: 48:5b:39:36:a2:73:00:00:00:00:00:00:00:00:00:00
> SNAME: .
> FNAME: .
> OPTION: 53 ( 1) DHCP message type 1 (DHCPDISCOVER)
> OPTION: 50 ( 4) Request IP address 172.16.33.121
> OPTION: 12 ( 6) Host name laptop
> OPTION: 55 ( 13) Parameter Request List 1 (Subnet mask)
> 28 (Broadcast address)
> 2 (Time offset)
> 3 (Routers)
> 15 (Domainname)
> 6 (DNS server)
> 119 (Domain Search)
> 12 (Host name)
> 44 (NetBIOS name server)
> 47 (NetBIOS scope)
> 26 (Interface MTU)
> 121 (Classless Static Route)
> 42 (NTP servers)
>
> OPTION: 82 ( 18) Relay Agent Information
> Circuit-ID 00:04:00:02:00:10
> Remote-ID 00:06:1c:bd:b9:9b:68:5c
> ---------------------------------------------------------------------------
So, you need persuade your relay to add a sub-option 5 (subnet select)
to the relay agent information, along with the circuit-id and remote-id.
The subnet-select option holds the 10....... network address and tells
dnsmasq it should allocate addresses there, even thought the giaddr is
on 172....
HTH
Simon.
More information about the Dnsmasq-discuss
mailing list