[Dnsmasq-discuss] bug:DHCP Relay not responding with DHCP OFFER.
Jason Kary
jkary_98 at yahoo.com
Mon May 1 00:27:12 BST 2017
Hello,
The VLAN setup is pretty basic:
interface Vlan1001
no shutdown
mtu 9216
no ip redirects
ip address 10.168.101.1/24
interface Vlan1002
no shutdown
mtu 9216
no ip redirects
ip address 10.168.102.1/24
ip dhcp relay address 10.168.101.20
ip dhcp relay source-interface Vlan1002
Single host running ESXi connected to single router.
Take Care
Jason
> On Apr 28, 2017, at 5:36 PM, Simon Kelley <simon at thekelleys.org.uk> wrote:
>
> On 27/04/17 22:02, Jason Kary wrote:
>> Hi Folks,
>>
>> I have a basic setup for DHCP relay across VLANS in DNSMASQ.
>>
>> My configuration file looks like:
>>
>>
>> bogus-priv
>> interface=ens160
>> log-dhcp
>> dhcp-range=10.168.102.100,10.168.102.150,255.255.255.0,12h
>>
>>
>> The client and server are running on a VMs in separate VLANS. DHCP
>> requests appear to be coming across:
>>
>>
>> root at DHCP-UBUNTU-SERVER:~# tcpdump -i ens160 port 67 or port 68 -n
>> tcpdump: verbose output suppressed, use -v or -vv for full protocol
>> decode
>> listening on ens160, link-type EN10MB (Ethernet), capture size
>> 262144 bytes
>> 03:58:40.966944 IP 10.168.102.1.67 > 10.168.101.20.67: BOOTP/DHCP,
>> Request from 00:0c:29:65:e0:ea, length 322
>> 03:58:46.487767 IP 10.168.102.1.67 > 10.168.101.20.67: BOOTP/DHCP,
>> Request from 00:0c:29:65:e0:ea, length 322
>> 03:58:54.424895 IP 10.168.102.1.67 > 10.168.101.20.67: BOOTP/DHCP,
>> Request from 00:0c:29:65:e0:ea, length 322
>> 03:59:07.795712 IP 10.168.102.1.67 > 10.168.101.20.67: BOOTP/DHCP,
>> Request from 00:0c:29:65:e0:ea, length 322
>> 03:59:19.196022 IP 10.168.102.1.67 > 10.168.101.20.67: BOOTP/DHCP,
>> Request from 00:0c:29:65:e0:ea, length 322
>>
>> root at DHCP-UBUNTU-SERVER:~# iptables -L
>> Chain INPUT (policy ACCEPT)
>> target prot opt source destination
>>
>> Chain FORWARD (policy ACCEPT)
>> target prot opt source destination
>>
>> Chain OUTPUT (policy ACCEPT)
>> target prot opt source destination
>> root at DHCP-UBUNTU-SERVER:~#
>>
>>
>> The syslog log indicates the DCHP OFFERS are ‘supposed’ to be going out
>> however nothing is seen on the wire.
>>
>>
>> Apr 27 04:03:26 DHCP-UBUNTU-SERVER dnsmasq-dhcp[17767]: 1121794364
>> available DHCP range: 10.168.102.100 -- 10.168.102.150
>> Apr 27 04:03:29 DHCP-UBUNTU-SERVER dnsmasq-dhcp[17767]: 1121794364
>> DHCPDISCOVER(ens160) 00:0c:29:65:e0:ea
>> Apr 27 04:03:29 DHCP-UBUNTU-SERVER dnsmasq-dhcp[17767]: 1121794364
>> tags: ens160
>> Apr 27 04:03:29 DHCP-UBUNTU-SERVER dnsmasq-dhcp[17767]: 1121794364
>> DHCPOFFER(ens160) 10.168.102.128 00:0c:29:65:e0:ea
>> Apr 27 04:03:29 DHCP-UBUNTU-SERVER dnsmasq-dhcp[17767]: 1121794364
>> requested options: 1:netmask, 28:broadcast, 2:time-offset,
>> 121:classless-static-route,
>> Apr 27 04:03:29 DHCP-UBUNTU-SERVER dnsmasq-dhcp[17767]: 1121794364
>> requested options: 15:domain-name, 6:dns-server, 12:hostname,
>> Apr 27 04:03:29 DHCP-UBUNTU-SERVER dnsmasq-dhcp[17767]: 1121794364
>> requested options: 40:nis-domain, 41:nis-server, 42:ntp-server,
>> Apr 27 04:03:29 DHCP-UBUNTU-SERVER dnsmasq-dhcp[17767]: 1121794364
>> requested options: 26:mtu, 119:domain-search, 3:router,
>> 121:classless-static-route,
>> Apr 27 04:03:29 DHCP-UBUNTU-SERVER dnsmasq-dhcp[17767]: 1121794364
>> requested options: 249, 33:static-route, 252, 42:ntp-server
>> Apr 27 04:03:29 DHCP-UBUNTU-SERVER dnsmasq-dhcp[17767]: 1121794364
>> next server: 10.168.101.20
>> Apr 27 04:03:29 DHCP-UBUNTU-SERVER dnsmasq-dhcp[17767]: 1121794364
>> sent size: 1 option: 53 message-type 2
>> Apr 27 04:03:29 DHCP-UBUNTU-SERVER dnsmasq-dhcp[17767]: 1121794364
>> sent size: 4 option: 54 server-identifier 10.168.101.20
>> Apr 27 04:03:29 DHCP-UBUNTU-SERVER dnsmasq-dhcp[17767]: 1121794364
>> sent size: 4 option: 51 lease-time 12h
>> Apr 27 04:03:29 DHCP-UBUNTU-SERVER dnsmasq-dhcp[17767]: 1121794364
>> sent size: 4 option: 58 T1 6h
>> Apr 27 04:03:29 DHCP-UBUNTU-SERVER dnsmasq-dhcp[17767]: 1121794364
>> sent size: 4 option: 59 T2 10h30m
>> Apr 27 04:03:29 DHCP-UBUNTU-SERVER dnsmasq-dhcp[17767]: 1121794364
>> sent size: 4 option: 1 netmask 255.255.255.0
>> Apr 27 04:03:29 DHCP-UBUNTU-SERVER dnsmasq-dhcp[17767]: 1121794364
>> sent size: 4 option: 28 broadcast 10.168.102.255
>> Apr 27 04:03:29 DHCP-UBUNTU-SERVER dnsmasq-dhcp[17767]: 1121794364
>> sent size: 4 option: 3 router 10.168.102.1
>> Apr 27 04:03:29 DHCP-UBUNTU-SERVER dnsmasq-dhcp[17767]: 1121794364
>> sent size: 4 option: 6 dns-server 10.168.101.20
>> Apr 27 04:03:29 DHCP-UBUNTU-SERVER dnsmasq-dhcp[17767]: 1121794364
>> sent size: 20 option: 82 agent-id
>> 01:0a:01:08:00:06:00:4c:4f:2a:00:2f:02:06…
>>
>>
>> I’ve been trying to trace this issue and it is like the sendmsg system
>> call is not working properly. I believe routing is setup properly on
>> the DHCP server.
>>
>> root at DHCP-UBUNTU-SERVER:~# netstat -nr
>> Kernel IP routing table
>> Destination Gateway Genmask Flags MSS Window
>> irtt Iface
>> 0.0.0.0 172.31.13.1 0.0.0.0 UG 0 0
>> 0 ens192
>> 10.168.101.0 0.0.0.0 255.255.255.0 U 0 0
>> 0 ens160
>> 10.168.102.0 0.0.0.0 255.255.255.0 U 0 0
>> 0 ens160
>> 172.31.13.0 0.0.0.0 255.255.255.0 U 0 0
>> 0 ens192
>> root at DHCP-UBUNTU-SERVER:~#
>>
>> Can anyone seen something obvious that I am doing wrong?
>>
>>
>
>
> What's the interface/vlan configuration?
> Where is the DHCP relay running and how is it configured?
>
> Cheers,
>
> Simon.
>
>
>
>
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