[Dnsmasq-discuss] bug:DHCP Relay not responding with DHCP OFFER.
Dan Sneddon
dsneddon at redhat.com
Mon May 1 19:35:24 BST 2017
Your routing table is wrong. You have both 10.168.101.0/24 and
10.168.102.0/24 both set up as local subnets (see the 0.0.0.0 gateway).
The remote subnet should be routed through the local router, so your
route would appear something like this:
10.168.101.0 0.0.0.0 255.255.255.0 U 0 0 0 ens160
10.168.102.0 10.168.101.1 255.255.255.0 U 0 0 0 ens160
--
Dan Sneddon | Senior Principal Software Engineer
dsneddon at redhat.com | redhat.com/openstack
dsneddon:irc | @dxs:twitter
On 04/27/2017 02:02 PM, 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?
>
> Take Care
> Jason
>
>
> _______________________________________________
> Dnsmasq-discuss mailing list
> Dnsmasq-discuss at lists.thekelleys.org.uk
> http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
>
More information about the Dnsmasq-discuss
mailing list