[Dnsmasq-discuss] ignore mac address for one of the dhcp

Petr Menšík pemensik at redhat.com
Mon May 11 10:44:31 BST 2020


Hi John and Geert,

I think it has possible workaround with dnsmasq 2.81 release. Since
commit 52ec7836139[1], it is possible to define dhcp-host with a tag.
Therefore it should work defining the host with mac address of your
switch differently for both interfaces. Have not tested it on any my
setup however. If you do, please let us know. I were unable to find
version of used dnsmasq.

Examples are below in Geert's text.

1.
http://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=commit;h=52ec7836139e7a11374971905e5ac0d2d02e32c0

On 4/13/20 4:18 PM, John Siu wrote:
> On Mon, Apr 13, 2020 at 4:54 AM Geert Stappers <stappers at stappers.nl> wrote:
> 
>> On Sun, Apr 12, 2020 at 03:14:33PM -0400, John Siu wrote:
>>> I am running dnsmasq on a multiple port box. Following are dhcp config
>> for
>>> the lan and dmz ports:
>>>
>>> ---
>>>
>>> ## LAN
>>> dhcp-range=tag:lan,::1,constructor:lan,ra-names,72h # IPv6
>>> dhcp-range=tag:lan,172.16.168.130,172.16.168.250,72h # IPv4
>>> dhcp-option=tag:lan,option:router,172.16.168.1 # option 3 default gw
>>> dhcp-option=tag:lan,option:dns-server,172.16.168.1

>>>
>>> ## DMZ
>>> dhcp-range=tag:dmz,::1,constructor:dmz,ra-names,72h # IPv6
>>> dhcp-range=tag:dmz,10.10.10.100,10.10.10.120,72h # IPv4
>>> dhcp-option=tag:dmz,option:router,10.10.10.1 # option 3 default gw
>>> dhcp-option=tag:dmz,option:dns-server,10.10.10.1

>>>
>>> ---
>>>
>>> They work correctly for network connected to those ports.
>>
>> I wonder how.
>>
>> I mean: The provided information looks incomplete to me.
>> Might be due an attempt to make the config more generic.
>>
>>
>>
> Following is the complete 92-dhcp.conf file I am using. It is not generic.
> I have interface name "lan" and "dmz" setup in network config.
> ---
> log-dhcp
> quiet-dhcp
> quiet-dhcp6
> quiet-ra
> 
> enable-ra
> 
> ## LAN
> dhcp-range=tag:lan,::1,constructor:lan,ra-names,72h # IPv6
> dhcp-range=tag:lan,172.16.168.130,172.16.168.250,72h # IPv4
> dhcp-option=tag:lan,option:router,172.16.168.1 # option 3 default gw
> dhcp-option=tag:lan,option:dns-server,172.16.168.1 # option 6 dns
> #dhcp-option=tag:lan,option:ntp-server,172.16.168.1
dhcp-host=tag:lan,01:00:18:4D:C0:3F:0E,172.16.168.251,12h
> 
> ## DMZ
> dhcp-range=tag:dmz,::1,constructor:dmz,ra-names,72h # IPv6
> dhcp-range=tag:dmz,10.10.10.100,10.10.10.120,72h # IPv4
> dhcp-option=tag:dmz,option:router,10.10.10.1 # option 3 default gw
> dhcp-option=tag:dmz,option:dns-server,10.10.10.1 # option 6 dns
> #dhcp-option=tag:dmz,option:ntp-server,10.10.10.1
dhcp-host=tag:dmz,01:00:18:4D:C0:3F:0E,ignore
> 
> ## Lease
> dhcp-hostsfile=/etc/dnsmasq.d/extra/dhcp.hosts
> dhcp-leasefile=/etc/dnsmasq.d/extra/dhcp.lease
> ---
> 
>> However, I am having issue with the switch which connect to both dmz
>>> and lan ports with different VLANs. As those VLAN ports share the same
>>> mac address, sometimes the switch will pick up IP from the lan side,
>>> and sometimes from the dmz side.
>>>
>>> How can I make dnsmasq only serve IP on the lan side for this specific
>> mac
>>> address?
>>
>> Tell more about what you have.
>>
>> The switch is a Netgear GS908E. It has 8 ports. I setup 2 vlan, one for
> dmz, one for lan. So there is one cable from my server dmz port to the dmz
> vlan, same for lan. The switch is configure to use dhcp for its ip.
> However, it requests dhcp from all ports. As a result, sometime it pick up
> 172.x.x.x, and sometimes it pickup 10.x.x.x address.
> 
> 
>> Regards
>> Geert Stappers
>> --
>> Silence is hard to parse

Regards,
Petr

-- 
Petr Menšík
Software Engineer
Red Hat, http://www.redhat.com/
email: pemensik at redhat.com
PGP: DFCF908DB7C87E8E529925BC4931CA5B6C9FC5CB




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