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Today's Topics:
1. To send DHCPINFORM: from dhclient (Divakar Y)
2. Re: Reg: dhcp service unresponsive frequently (Purva Rawan)
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Message: 1
Date: Wed, 12 Feb 2020 18:26:24 +0530
From: Divakar Y <divakar.yadava...@gmail.com>
To: dhcp-users@lists.isc.org
Subject: To send DHCPINFORM: from dhclient
Message-ID:
<CAJRxWU0T4k=mw+5lmkdm_1fjr6-rhb06vr5y3zcmiyb0nsy...@mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"
Hello,
I am using isc-dhcp stack version dhcp-4.3.5.
I am intending to use DHCPINFORM to get vendor-options from the DHCP
server that has offered me the ip.
My dhclient.conf is as below:
#Option 50 (Address Request) - Previously used IP Address (if available)
# automatically sent
#Option 53 (Message Type) - Includes all applicable Client -->
Server Options
# automatically sent
#sending vendor class in option 60
send vendor-class-identifier \""$VENDOR_ID"\";
#option 61 sends the backplane id as client identifier, used
at server to provide specific attrs
send dhcp-client-identifier \""$CLIENT_ID"\";
#request the params from server
#request subnet-mask, routers, broadcast-address,
vendor-encapsulated-options;
request vendor-encapsulated-options;
#dhcp inform
send dhcp-message-type 8;
>From tcpdump, i am able to see that dhclient is sending:
[root@in-nelnx-dt ~]# tcpdump -i enp16s0 -vvXn port 67
tcpdump: listening on enp16s0, link-type EN10MB (Ethernet), capture
size 65535 bytes
17:15:50.369748 IP (tos 0x10, ttl 128, id 0, offset 0, flags [none],
proto UDP (17), length 328)
0.0.0.0.bootpc > 255.255.255.255.bootps: [udp sum ok] BOOTP/DHCP,
Request from 00:90:0b:76:00:cb, length 300, xid 0x94ab6216, Flags
[none] (0x0000)
Client-Ethernet-Address 00:90:0b:76:00:cb
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message Option 53, length 1: Inform
Lease-Time Option 51, length 4: 3600
Requested-IP Option 50, length 4: 192.168.2.213
Parameter-Request Option 55, length 1:
Vendor-Option
Vendor-Class Option 60, length 12: "MYDEPT%CARDTYPE"
Client-ID Option 61, length 18: hardware-type 50,
31:32:39:36:25:4d:41:39:30:31:33:35:31:30:30:38:39
0x0000: 4510 0148 0000 0000 8011 3996 0000 0000 E..H......9.....
0x0010: ffff ffff 0044 0043 0134 fcce 0101 0600 .....D.C.4......
0x0020: 94ab 6216 0000 0000 0000 0000 0000 0000 ..b.............
0x0030: 0000 0000 0000 0000 0090 0b76 00cb 0000 ...........v....
0x0040: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0x0050: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0x0060: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0x0070: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0x0080: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0x0090: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0x00a0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0x00b0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0x00c0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0x00d0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0x00e0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0x00f0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0x0100: 0000 0000 0000 0000 6382 5363 3501 0833 ........c.Sc5..3
0x0110: 0400 000e 1032 04c0 a802 d537 012b 3c0c .....2.....7.+<.
0x0120: 496e 6669 6e65 7261 254f 4c41 3d12 3231 MYDEPT%CARDTYPE=.21
0x0130: 3239 3625 4d41 3930 3133 3531 3030 3839 296%<SERIALNUM>
On checking the dhcpserver logs:
lnx-dt log]# tail -f messages
Feb 11 17:24:49 in-nelnx-dt dhcpd: DHCPREQUEST for 192.168.2.225 from
00:90:0b:4c:c8:e8 via enp16s0
Feb 11 17:24:49 in-nelnx-dt dhcpd: DHCPACK on 192.168.2.225 to
00:90:0b:4c:c8:e8 via enp16s0
Feb 11 17:25:00 in-nelnx-dt systemd-logind: Removed session 2838.
Feb 11 17:25:12 in-nelnx-dt systemd-logind: Removed session 2839.
Feb 11 17:25:19 in-nelnx-dt dhcpd: DHCPREQUEST for 192.168.2.213 from
00:90:0b:76:00:cb via enp16s0
Feb 11 17:25:19 in-nelnx-dt dhcpd: DHCPACK on 192.168.2.213 to
00:90:0b:76:00:cb via enp16s0
Feb 11 17:25:27 in-nelnx-dt dhcpd: DHCPINFORM from 0.0.0.0 via
enp16s0: ignored (null source address).
Feb 11 17:25:31 in-nelnx-dt dhcpd: DHCPINFORM from 0.0.0.0 via
enp16s0: ignored (null source address).
Feb 11 17:25:43 in-nelnx-dt dhcpd: DHCPINFORM from 0.0.0.0 via
enp16s0: ignored (null source address).
Feb 11 17:25:56 in-nelnx-dt dhcpd: DHCPINFORM from 0.0.0.0 via
enp16s0: ignored (null source address).
Feb 11 17:26:06 in-nelnx-dt dhcpd: DHCPINFORM from 0.0.0.0 via
enp16s0: ignored (null source address).
I observe the ciaddr is coming as 0.0.0.0 , which as RFC2131/2132,
should be valid value that contains the already offered IP.
I dont have relay, so I cant fill, giaddr.
But how do ensure to fill the ciaddr, from the dhclient.conf.
Also the script file:
https://github.com/greearb/dhcp-ct/blob/master/dhclient-script
Can you please guide me how I can do that.
Thanks,
divakar
------------------------------
Message: 2
Date: Thu, 13 Feb 2020 14:29:39 +0530 (IST)
From: Purva Rawan <pur...@cdac.in>
To: "Niall O'Reilly" <niall.orei...@ucd.ie>, Users of ISC DHCP
<dhcp-users@lists.isc.org>
Subject: Re: Reg: dhcp service unresponsive frequently
Message-ID:
<1791273153.550.1581584379534.javamail.open-xcha...@webmail.cdac.in>
Content-Type: text/plain; charset="utf-8"
On January 25, 2020 at 10:57 PM Niall O'Reilly <niall.orei...@ucd.ie> wrote:
> On 24 Jan 2020, at 7:14, Purva Rawan wrote:
>
> > We have not configured dhcp relay agent in both dhcp server's
> > configuration .
>
> That would be right; see below: the relay belongs to the network, not to
> the
> server.
>
> > In one of the server ,dhcp service listening on each interfaces.
> > For another dhcp server ,dhcp relay agent is serving through Layer 3
> > switch.
> >
> > But we are facing this issue for both the servers.
>
> It may help to think about this from the client back to the server,
> rather than from the server(s) outwards.
>
> I don't have a good picture of your network topology, or where the
> relays and servers are sitting, or what experience you have, so I may
> be explaining at the wrong level. If so, apologies.
>
> Each client is connected to a layer-2 network, and needs a local DHCP
> service on this network.
>
> The local DHCP service must be provided either by a relay or by a
> server;
> it's unusual to have a server connected to every client network.
>>>> Yes ,clients are connected to layer-2 network.
>
> The relay is typically part of the router configuration.
>
> Each relay must be configured with the address of one or more servers;
> one is enough; a second gives resilience; I wouldn't suggest more.
>
> The server(s) can be on a network where no clients are connected; except
> for very simple topologies, I prefer to keep the server on a non-client
> network.
>
> Each relay must be able to reach, and be reachable from, the server(s);
> access lists and routing errors can obstruct reachability, perhaps
> asymmetrically.
>
> Each client network must be specified in the server configuration.
>
> Log entries on the server will show you what the server thinks is going
> on.
> You should see the DORA sequence: DISCOVER, OFFER, REQUEST, ACK; for
> renewals, you'll normally just see REQUEST, ACK.
> >>>>>>> We are able to see DORA sequence in logs
> If you know or expect that the client is sending DISCOVER, but don't see
> it in the server log, then you'll need to look at your network and work
> out why the DISCOVER is not reaching the server either from the relay or
> from a client on the same network as the server.
>
> If you see OFFER in the server logs, but no REQUEST, you'll need to look
> at the network in the opposite direction, and work out why the OFFER is
> not reaching the client or relay.
>
It was working fine since last 6-7 years.But from last 3 4 months ,dhcp service
stops intermittently.
Point to be noted that the configuration of DHCP is in LDAP database.
We have observed following things when dhcp service stopped working suddenly
1. slapd service remains working and logs captured in slapd.logs file
2. dhcp logs not getting populated.
Regards,
Purva Rawan
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