DHCPD and option-82 problem
Chuck Anderson
cra at WPI.EDU
Thu May 22 12:58:15 UTC 2014
If your capture was from the DHCP server end, and it shows the
Option-82 in the capture for the packet coming in from the client
through the relay, but the server doesn't log anything about the
match, then I don't think the problem could be with the switch or
router or relay-agent. It sounds like a code problem (bug) with
dhcpd.
On Thu, May 22, 2014 at 07:53:12AM -0400, Denis Laventure wrote:
> Good catch Glenn! :)
>
> Yeah this was my fault, I had log from RESD-4D but capture from RESD-4B... I changed the MAC on the capture log to post it here so no one would see it, but I forgot to change the option-82 string. I should have double-checked before posting :)
>
> Anyway the problem is the same with the right string.
>
> I will continue to investigate with the "ip dhcp snooping trust" like Joseph suggested, perhaps this is a case for a TAC call... I have the problem with 2 type of cisco switches with different IOS version (12.x vs 15.x)...
>
> Thanks,
> Denis
>
> -----Message d'origine-----
> De : dhcp-users-bounces at lists.isc.org [mailto:dhcp-users-bounces at lists.isc.org] De la part de Glenn Satchell
> Envoyé : 22 mai 2014 04:11
> À : Users of ISC DHCP
> Objet : RE: DHCPD and option-82 problem
>
> The circuit-id is different between the dhcpd.conf and the packet capture.
> Last number is 44 in dhcpd.conf and 42 in tcpdump output. Is that just a copy/paste error or might be significant?
>
> class "RESD-4D" {
> match if option agent.circuit-id=1:7:52:45:53:44:2d:34:44;
>
> Agent Circuit ID: 0107524553442d3442
>
> regards,
> -glenn
>
> On Thu, May 22, 2014 3:19 am, Denis Laventure wrote:
> > Just to clarify, I have done this for several years now. I used Method
> > 1 and/or Method 2 without problem. I just found out by some clients
> > that sometimes it doesn't work with there device (about 20 clients /
> > PC, Mac, Router, etc).
> >
> > When the packet get to the dhcp server, it contains option-82 (checked
> > by
> > tcpdump) but I get no log from my dhcp daemon using this log statement
> > in dhcpd.conf :
> >
> > if exists agent.circuit-id {
> > log (info, concat("DEBUG: (option-82 raw) ", client-mac-address, " -
> > ", binary-to-ascii (16, 8, ":", option agent.circuit-id))); }
> >
> > When option-82 get used and the client get an IP, I see the log from
> > this statement, but when I get the no free leases error, there's no
> > option-82 log... The daemon doesn't seems to recognize option-82...
> > But tcpdump/wireshark decodes the option-82 from the same DHCPDISCOVER
> > without problem.
> >
> > Thanks,
> > Denis Laventure
> >
> > De : dhcp-users-bounces at lists.isc.org
> > [mailto:dhcp-users-bounces at lists.isc.org] De la part de Denis
> > Laventure Envoyé : 21 mai 2014 12:08 À : dhcp-users at lists.isc.org
> > Objet : DHCPD and option-82 problem
> >
> > Hi,
> >
> > We have about 300 connections on our university dormitory and we use
> > option-82 to assign one fixed IP to every chamber.
> > Everything works fine but I sometimes find that some clients don't get
> > an IP and keep sending DHCPDISCOVER continually. Sometimes it's a
> > Windows 7 client, sometimes it's a D-LINK Router or a Mac.
> >
> > I captured the requests from one client and everything seems normal,
> > it even have option-82 inserted by the relay.
> > In my dhcpd log, the dhcpd daemon doesn't decode it option-82 and the
> > option agent.circuit-id is empty. (tcpdump/wireshark capture below) I
> > get the usual "no free leases" since option-82 isn't recognized.
> > (dhcpd log below)
> >
> > Is there a way to debug received DHCPDICOVER packets (other than log
> > or
> > tcpdump) that I could check to make sure option-82 is present and
> > decoded by the daemon?
> > Why dhcp daemon doesn't decode option-82 if it's in the packet?
> >
> > I'm on Linux RHEL 5.10 and using ISC DHCPD version 4.3.0 (in
> > failover). I tried downgrading to version 4.2.0 and I have the same problem.
> >
> > For now, I'm using a Cisco 3560 as dhcp server with option-82 and all
> > the clients (even the ones that don't work with isc dhcpd) works. I
> > don't want to keep using the Cisco router for dhcp, I want to return
> > to my isc dhcp server but I can't because of that problem...
> >
> > Thanks,
> > Denis Laventure
> >
> > ======================================================================
> > ==========================================
> >
> > Aditional informations:
> >
> > Client Switch: cisco WS-C2960S-F48TS-L
> >
> > sh ver
> > Cisco IOS Software, C2960S Software (C2960S-UNIVERSALK9-M), Version
> > 15.2(1)E2, RELEASE SOFTWARE (fc1)
> >
> > interface FastEthernet2/0/17
> > ip dhcp snooping vlan 261 information option format-type circuit-id
> > string RESD-4D
> >
> >
> > ======================================================================
> > ==========================================
> >
> > Method 1 (Class and Pool):
> >
> > subnet 172.17.11.0 netmask 255.255.255.0 {
> > ...
> > pool { range 172.17.11.80; allow members of "RESD-4D"; }
> > ...
> > }
> >
> > set client-mac-address = concat (
> > suffix (concat ("0", binary-to-ascii (16, 8, "",
> > substring(hardware,1,1))),2), ":",
> > suffix (concat ("0", binary-to-ascii (16, 8, "",
> > substring(hardware,2,1))),2), ":",
> > suffix (concat ("0", binary-to-ascii (16, 8, "",
> > substring(hardware,3,1))),2), ":",
> > suffix (concat ("0", binary-to-ascii (16, 8, "",
> > substring(hardware,4,1))),2), ":",
> > suffix (concat ("0", binary-to-ascii (16, 8, "",
> > substring(hardware,5,1))),2), ":",
> > suffix (concat ("0", binary-to-ascii (16, 8, "",
> > substring(hardware,6,1))),2)
> > );
> >
> > class "RESD-4D" {match if option
> > agent.circuit-id=1:7:52:45:53:44:2d:34:44; log(info,concat("DEBUG:
> > RESD-4D ",client-mac-address));}
> >
> > Result:
> > ...
> > May 6 16:41:23 dhcpa dhcpd: DHCPDISCOVER from 74:d0:2b:e9:82:0d via
> > 172.17.11.1: network 172.17.11.0/24: no free leases May 6 16:41:54
> > dhcpa dhcpd: DHCPDISCOVER from 74:d0:2b:e9:82:0d via
> > 172.17.11.1: network 172.17.11.0/24: no free leases May 6 16:41:59
> > dhcpa dhcpd: DHCPDISCOVER from 74:d0:2b:e9:82:0d via
> > 172.17.11.1: network 172.17.11.0/24: no free leases ...
> >
> > Working client get:
> > May 6 08:14:07 dhcpa dhcpd: DEBUG: (client info) 172.17.11.79 -
> > 74:86:7a:2b:90:16 - MSFT 5.0 - 1,f,3,6,2c,2e,2f,1f,21,79,f9,fc,2b
> > May 6 08:14:07 dhcpa dhcpd: DEBUG: (option-82 raw) 74:86:7a:2b:90:16
> > -
> > 1:7:52:45:53:44:2d:34:43
> > May 6 08:14:07 dhcpa dhcpd: DEBUG: RESD-4C 74:86:7a:2b:90:16 May 6
> > 08:14:07 dhcpa dhcpd: DHCPDISCOVER from 74:86:7a:2b:90:16 via
> > 172.17.11.1
> > May 6 08:14:07 dhcpa dhcpd: DHCPOFFER on 172.17.11.79 to
> > 74:86:7a:2b:90:16 (Inspiron3521) via 172.17.11.1 May 6 08:14:07 dhcpa
> > dhcpd: DEBUG: (client info) 172.17.11.79 -
> > 74:86:7a:2b:90:16 - MSFT 5.0 - 1,f,3,6,2c,2e,2f,1f,21,79,f9,fc,2b
> > May 6 08:14:07 dhcpa dhcpd: DEBUG: (option-82 raw) 74:86:7a:2b:90:16
> > -
> > 1:7:52:45:53:44:2d:34:43
> > May 6 08:14:07 dhcpa dhcpd: DEBUG: (option-82 cid) IP:172.17.11.79,
> > MAC:74:86:7a:2b:90:16, CID:1:7:52:45:53:44:2d:34:43 May 6 08:14:07
> > dhcpa dhcpd: DEBUG: RESD-4C 74:86:7a:2b:90:16 May 6 08:14:07 dhcpa
> > dhcpd: DHCPREQUEST for 172.17.11.79 (192.168.1.10) from
> > 74:86:7a:2b:90:16 (Inspiron3521) via 172.17.11.1 May 6 08:14:07 dhcpa
> > dhcpd: DHCPACK on 172.17.11.79 to 74:86:7a:2b:90:16
> > (Inspiron3521) via 172.17.11.1
> >
> > ======================================================================
> > ==========================================
> >
> > Method 2 (host-identifier):
> >
> > host RESD-4D { host-identifier option agent.circuit-id
> > 1:7:52:45:53:44:2d:34:44; fixed-address 172.17.11.80; }
> >
> > Result:
> > ...
> > May 6 17:02:37 dhcpa dhcpd: DHCPDISCOVER from 74:d0:2b:e9:82:0d via
> > 172.17.11.1: network 172.17.11.0/24: no free leases May 6 17:02:54
> > dhcpa dhcpd: DHCPDISCOVER from 74:d0:2b:e9:82:0d via
> > 172.17.11.1: network 172.17.11.0/24: no free leases May 6 17:03:26
> > dhcpa dhcpd: DHCPDISCOVER from 74:d0:2b:e9:82:0d via
> > 172.17.11.1: network 172.17.11.0/24: no free leases ...
> >
> > ======================================================================
> > ==========================================
> >
> > TCPDUMP/WIRESHARK LOG (5 DHCPDISCOVER)
> >
> > No. Time Source Destination Protocol
> > Length Info
> > 1 0.000000 172.17.11.1 192.168.1.10 DHCP
> > 352 DHCP Discover - Transaction ID 0xcab50e69
> >
> > Frame 1: 352 bytes on wire (2816 bits), 352 bytes captured (2816 bits)
> > Ethernet II, Src: 10:8c:cf:28:5a:40 (10:8c:cf:28:5a:40), Dst:
> > 00:1e:c9:d7:2c:d8 (00:1e:c9:d7:2c:d8)
> > Internet Protocol Version 4, Src: 172.17.11.1 (172.17.11.1), Dst:
> > 192.168.1.10 (192.168.1.10)
> > User Datagram Protocol, Src Port: 67 (67), Dst Port: 67 (67) Bootstrap
> > Protocol
> > Message type: Boot Request (1)
> > Hardware type: Ethernet (0x01)
> > Hardware address length: 6
> > Hops: 1
> > Transaction ID: 0xcab50e69
> > Seconds elapsed: 0
> > Bootp flags: 0x8000 (Broadcast)
> > Client IP address: 0.0.0.0 (0.0.0.0)
> > Your (client) IP address: 0.0.0.0 (0.0.0.0)
> > Next server IP address: 0.0.0.0 (0.0.0.0)
> > Relay agent IP address: 172.17.11.1 (172.17.11.1)
> > Client MAC address: 74:d0:2b:e9:82:0d (74:d0:2b:e9:82:0d)
> > Client hardware address padding: 00000000000000000000
> > Server host name not given
> > Boot file name not given
> > Magic cookie: DHCP
> > Option: (53) DHCP Message Type
> > Length: 1
> > DHCP: Discover (1)
> > Option: (61) Client identifier
> > Length: 7
> > Hardware type: Ethernet (0x01)
> > Client MAC address: 74:d0:2b:e9:82:0d (74:d0:2b:e9:82:0d)
> > Option: (12) Host Name
> > Length: 7
> > Host Name: SAMSUNG
> > Option: (60) Vendor class identifier
> > Length: 8
> > Vendor class identifier: MSFT 5.0
> > Option: (55) Parameter Request List
> > Length: 13
> > Parameter Request List Item: (1) Subnet Mask
> > Parameter Request List Item: (15) Domain Name
> > Parameter Request List Item: (3) Router
> > Parameter Request List Item: (6) Domain Name Server
> > Parameter Request List Item: (44) NetBIOS over TCP/IP Name Server
> > Parameter Request List Item: (46) NetBIOS over TCP/IP Node Type
> > Parameter Request List Item: (47) NetBIOS over TCP/IP Scope
> > Parameter Request List Item: (31) Perform Router Discover
> > Parameter Request List Item: (33) Static Route
> > Parameter Request List Item: (121) Classless Static Route
> > Parameter Request List Item: (249) Private/Classless Static
> > Route
> > (Microsoft)
> > Parameter Request List Item: (252) Private/Proxy autodiscovery
> > Parameter Request List Item: (43) Vendor-Specific Information
> > Option: (82) Agent Information Option
> > Length: 21
> > Option 82 Suboption: (1) Agent Circuit ID
> > Length: 9
> > Agent Circuit ID: 0107524553442d3442
> > Option 82 Suboption: (2) Agent Remote ID
> > Length: 8
> > Agent Remote ID: 0006f84f5742d700
> > Option: (255) End
> > Option End: 255
> >
> > No. Time Source Destination Protocol
> > Length Info
> > 2 4.944200 172.17.11.1 192.168.1.10 DHCP
> > 352 DHCP Discover - Transaction ID 0xcab50e69
> >
> > Frame 2: 352 bytes on wire (2816 bits), 352 bytes captured (2816 bits)
> > Ethernet II, Src: 10:8c:cf:28:5a:40 (10:8c:cf:28:5a:40), Dst:
> > 00:1e:c9:d7:2c:d8 (00:1e:c9:d7:2c:d8)
> > Internet Protocol Version 4, Src: 172.17.11.1 (172.17.11.1), Dst:
> > 192.168.1.10 (192.168.1.10)
> > User Datagram Protocol, Src Port: 67 (67), Dst Port: 67 (67) Bootstrap
> > Protocol
> > Message type: Boot Request (1)
> > Hardware type: Ethernet (0x01)
> > Hardware address length: 6
> > Hops: 1
> > Transaction ID: 0xcab50e69
> > Seconds elapsed: 4
> > Bootp flags: 0x8000 (Broadcast)
> > Client IP address: 0.0.0.0 (0.0.0.0)
> > Your (client) IP address: 0.0.0.0 (0.0.0.0)
> > Next server IP address: 0.0.0.0 (0.0.0.0)
> > Relay agent IP address: 172.17.11.1 (172.17.11.1)
> > Client MAC address: 74:d0:2b:e9:82:0d (74:d0:2b:e9:82:0d)
> > Client hardware address padding: 00000000000000000000
> > Server host name not given
> > Boot file name not given
> > Magic cookie: DHCP
> > Option: (53) DHCP Message Type
> > Length: 1
> > DHCP: Discover (1)
> > Option: (61) Client identifier
> > Length: 7
> > Hardware type: Ethernet (0x01)
> > Client MAC address: 74:d0:2b:e9:82:0d (74:d0:2b:e9:82:0d)
> > Option: (12) Host Name
> > Length: 7
> > Host Name: SAMSUNG
> > Option: (60) Vendor class identifier
> > Length: 8
> > Vendor class identifier: MSFT 5.0
> > Option: (55) Parameter Request List
> > Length: 13
> > Parameter Request List Item: (1) Subnet Mask
> > Parameter Request List Item: (15) Domain Name
> > Parameter Request List Item: (3) Router
> > Parameter Request List Item: (6) Domain Name Server
> > Parameter Request List Item: (44) NetBIOS over TCP/IP Name Server
> > Parameter Request List Item: (46) NetBIOS over TCP/IP Node Type
> > Parameter Request List Item: (47) NetBIOS over TCP/IP Scope
> > Parameter Request List Item: (31) Perform Router Discover
> > Parameter Request List Item: (33) Static Route
> > Parameter Request List Item: (121) Classless Static Route
> > Parameter Request List Item: (249) Private/Classless Static
> > Route
> > (Microsoft)
> > Parameter Request List Item: (252) Private/Proxy autodiscovery
> > Parameter Request List Item: (43) Vendor-Specific Information
> > Option: (82) Agent Information Option
> > Length: 21
> > Option 82 Suboption: (1) Agent Circuit ID
> > Length: 9
> > Agent Circuit ID: 0107524553442d3442
> > Option 82 Suboption: (2) Agent Remote ID
> > Length: 8
> > Agent Remote ID: 0006f84f5742d700
> > Option: (255) End
> > Option End: 255
> >
> > No. Time Source Destination Protocol
> > Length Info
> > 3 17.047575 172.17.11.1 192.168.1.10 DHCP
> > 352 DHCP Discover - Transaction ID 0xa2024d9e
> >
> > Frame 3: 352 bytes on wire (2816 bits), 352 bytes captured (2816 bits)
> > Ethernet II, Src: 10:8c:cf:28:5a:40 (10:8c:cf:28:5a:40), Dst:
> > 00:1e:c9:d7:2c:d8 (00:1e:c9:d7:2c:d8)
> > Internet Protocol Version 4, Src: 172.17.11.1 (172.17.11.1), Dst:
> > 192.168.1.10 (192.168.1.10)
> > User Datagram Protocol, Src Port: 67 (67), Dst Port: 67 (67) Bootstrap
> > Protocol
> > Message type: Boot Request (1)
> > Hardware type: Ethernet (0x01)
> > Hardware address length: 6
> > Hops: 1
> > Transaction ID: 0xa2024d9e
> > Seconds elapsed: 0
> > Bootp flags: 0x0000 (Unicast)
> > Client IP address: 0.0.0.0 (0.0.0.0)
> > Your (client) IP address: 0.0.0.0 (0.0.0.0)
> > Next server IP address: 0.0.0.0 (0.0.0.0)
> > Relay agent IP address: 172.17.11.1 (172.17.11.1)
> > Client MAC address: 74:d0:2b:e9:82:0d (74:d0:2b:e9:82:0d)
> > Client hardware address padding: 00000000000000000000
> > Server host name not given
> > Boot file name not given
> > Magic cookie: DHCP
> > Option: (53) DHCP Message Type
> > Length: 1
> > DHCP: Discover (1)
> > Option: (61) Client identifier
> > Length: 7
> > Hardware type: Ethernet (0x01)
> > Client MAC address: 74:d0:2b:e9:82:0d (74:d0:2b:e9:82:0d)
> > Option: (12) Host Name
> > Length: 7
> > Host Name: SAMSUNG
> > Option: (60) Vendor class identifier
> > Length: 8
> > Vendor class identifier: MSFT 5.0
> > Option: (55) Parameter Request List
> > Length: 13
> > Parameter Request List Item: (1) Subnet Mask
> > Parameter Request List Item: (15) Domain Name
> > Parameter Request List Item: (3) Router
> > Parameter Request List Item: (6) Domain Name Server
> > Parameter Request List Item: (44) NetBIOS over TCP/IP Name Server
> > Parameter Request List Item: (46) NetBIOS over TCP/IP Node Type
> > Parameter Request List Item: (47) NetBIOS over TCP/IP Scope
> > Parameter Request List Item: (31) Perform Router Discover
> > Parameter Request List Item: (33) Static Route
> > Parameter Request List Item: (121) Classless Static Route
> > Parameter Request List Item: (249) Private/Classless Static
> > Route
> > (Microsoft)
> > Parameter Request List Item: (252) Private/Proxy autodiscovery
> > Parameter Request List Item: (43) Vendor-Specific Information
> > Option: (82) Agent Information Option
> > Length: 21
> > Option 82 Suboption: (1) Agent Circuit ID
> > Length: 9
> > Agent Circuit ID: 0107524553442d3442
> > Option 82 Suboption: (2) Agent Remote ID
> > Length: 8
> > Agent Remote ID: 0006f84f5742d700
> > Option: (255) End
> > Option End: 255
> >
> > No. Time Source Destination Protocol
> > Length Info
> > 4 20.667474 172.17.11.1 192.168.1.10 DHCP
> > 352 DHCP Discover - Transaction ID 0xa2024d9e
> >
> > Frame 4: 352 bytes on wire (2816 bits), 352 bytes captured (2816 bits)
> > Ethernet II, Src: 10:8c:cf:28:5a:40 (10:8c:cf:28:5a:40), Dst:
> > 00:1e:c9:d7:2c:d8 (00:1e:c9:d7:2c:d8)
> > Internet Protocol Version 4, Src: 172.17.11.1 (172.17.11.1), Dst:
> > 192.168.1.10 (192.168.1.10)
> > User Datagram Protocol, Src Port: 67 (67), Dst Port: 67 (67) Bootstrap
> > Protocol
> > Message type: Boot Request (1)
> > Hardware type: Ethernet (0x01)
> > Hardware address length: 6
> > Hops: 1
> > Transaction ID: 0xa2024d9e
> > Seconds elapsed: 3
> > Bootp flags: 0x0000 (Unicast)
> > Client IP address: 0.0.0.0 (0.0.0.0)
> > Your (client) IP address: 0.0.0.0 (0.0.0.0)
> > Next server IP address: 0.0.0.0 (0.0.0.0)
> > Relay agent IP address: 172.17.11.1 (172.17.11.1)
> > Client MAC address: 74:d0:2b:e9:82:0d (74:d0:2b:e9:82:0d)
> > Client hardware address padding: 00000000000000000000
> > Server host name not given
> > Boot file name not given
> > Magic cookie: DHCP
> > Option: (53) DHCP Message Type
> > Length: 1
> > DHCP: Discover (1)
> > Option: (61) Client identifier
> > Length: 7
> > Hardware type: Ethernet (0x01)
> > Client MAC address: 74:d0:2b:e9:82:0d (74:d0:2b:e9:82:0d)
> > Option: (12) Host Name
> > Length: 7
> > Host Name: SAMSUNG
> > Option: (60) Vendor class identifier
> > Length: 8
> > Vendor class identifier: MSFT 5.0
> > Option: (55) Parameter Request List
> > Length: 13
> > Parameter Request List Item: (1) Subnet Mask
> > Parameter Request List Item: (15) Domain Name
> > Parameter Request List Item: (3) Router
> > Parameter Request List Item: (6) Domain Name Server
> > Parameter Request List Item: (44) NetBIOS over TCP/IP Name Server
> > Parameter Request List Item: (46) NetBIOS over TCP/IP Node Type
> > Parameter Request List Item: (47) NetBIOS over TCP/IP Scope
> > Parameter Request List Item: (31) Perform Router Discover
> > Parameter Request List Item: (33) Static Route
> > Parameter Request List Item: (121) Classless Static Route
> > Parameter Request List Item: (249) Private/Classless Static
> > Route
> > (Microsoft)
> > Parameter Request List Item: (252) Private/Proxy autodiscovery
> > Parameter Request List Item: (43) Vendor-Specific Information
> > Option: (82) Agent Information Option
> > Length: 21
> > Option 82 Suboption: (1) Agent Circuit ID
> > Length: 9
> > Agent Circuit ID: 0107524553442d3442
> > Option 82 Suboption: (2) Agent Remote ID
> > Length: 8
> > Agent Remote ID: 0006f84f5742d700
> > Option: (255) End
> > Option End: 255
> >
> > No. Time Source Destination Protocol
> > Length Info
> > 5 28.074747 172.17.11.1 192.168.1.10 DHCP
> > 352 DHCP Discover - Transaction ID 0xa2024d9e
> >
> > Frame 5: 352 bytes on wire (2816 bits), 352 bytes captured (2816 bits)
> > Ethernet II, Src: 10:8c:cf:28:5a:40 (10:8c:cf:28:5a:40), Dst:
> > 00:1e:c9:d7:2c:d8 (00:1e:c9:d7:2c:d8)
> > Internet Protocol Version 4, Src: 172.17.11.1 (172.17.11.1), Dst:
> > 192.168.1.10 (192.168.1.10)
> > User Datagram Protocol, Src Port: 67 (67), Dst Port: 67 (67) Bootstrap
> > Protocol
> > Message type: Boot Request (1)
> > Hardware type: Ethernet (0x01)
> > Hardware address length: 6
> > Hops: 1
> > Transaction ID: 0xa2024d9e
> > Seconds elapsed: 11
> > Bootp flags: 0x0000 (Unicast)
> > Client IP address: 0.0.0.0 (0.0.0.0)
> > Your (client) IP address: 0.0.0.0 (0.0.0.0)
> > Next server IP address: 0.0.0.0 (0.0.0.0)
> > Relay agent IP address: 172.17.11.1 (172.17.11.1)
> > Client MAC address: 74:d0:2b:e9:82:0d (74:d0:2b:e9:82:0d)
> > Client hardware address padding: 00000000000000000000
> > Server host name not given
> > Boot file name not given
> > Magic cookie: DHCP
> > Option: (53) DHCP Message Type
> > Length: 1
> > DHCP: Discover (1)
> > Option: (61) Client identifier
> > Length: 7
> > Hardware type: Ethernet (0x01)
> > Client MAC address: 74:d0:2b:e9:82:0d (74:d0:2b:e9:82:0d)
> > Option: (12) Host Name
> > Length: 7
> > Host Name: SAMSUNG
> > Option: (60) Vendor class identifier
> > Length: 8
> > Vendor class identifier: MSFT 5.0
> > Option: (55) Parameter Request List
> > Length: 13
> > Parameter Request List Item: (1) Subnet Mask
> > Parameter Request List Item: (15) Domain Name
> > Parameter Request List Item: (3) Router
> > Parameter Request List Item: (6) Domain Name Server
> > Parameter Request List Item: (44) NetBIOS over TCP/IP Name Server
> > Parameter Request List Item: (46) NetBIOS over TCP/IP Node Type
> > Parameter Request List Item: (47) NetBIOS over TCP/IP Scope
> > Parameter Request List Item: (31) Perform Router Discover
> > Parameter Request List Item: (33) Static Route
> > Parameter Request List Item: (121) Classless Static Route
> > Parameter Request List Item: (249) Private/Classless Static
> > Route
> > (Microsoft)
> > Parameter Request List Item: (252) Private/Proxy autodiscovery
> > Parameter Request List Item: (43) Vendor-Specific Information
> > Option: (82) Agent Information Option
> > Length: 21
> > Option 82 Suboption: (1) Agent Circuit ID
> > Length: 9
> > Agent Circuit ID: 0107524553442d3442
> > Option 82 Suboption: (2) Agent Remote ID
> > Length: 8
> > Agent Remote ID: 0006f84f5742d700
> > Option: (255) End
> > Option End: 255
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