difference between behavior after pxe and normal request and their definitions
Meike Stone
meike.stone at googlemail.com
Fri Jul 18 16:11:28 UTC 2014
Hello,
we set up a Citrix VDI environment and a few virtual desktops (PVS
Target devices) boots Windows from network (normally via pxe).
1) So at first, the (virtual) NIC from the PVS target device discovers
and request an IP address and getting the boot image via tftp
2) Second, during later booting the OS (Windows), the client network
stack discover and request an IP address again (same mac).
a) Normaly, the DHCP Server should hand out two different IP
addresses, if the first lease (from 1)) is not expired.
That works as expected (normal network boot without pxe).
b) With a PXE request in 1), the client gets in 2) the same address
like in 1), regardless whether the lease in 1) is expired or not.
Both are normal, but my question is, where can I find the definitions
(RFC) for this behavior regarding pxe in the dhcp protocol? I did
nothing found until now?
The manual page from dhcp.conf does nothing write about this...
Citrix only made a small comment in their knowledge base :
http://support.citrix.com/article/CTX139873
Thanks Meike, have nice weekend!
===============================================
Examples (only Discover and Offer)
(hope, I made no mistake during clean up ...)
===============================================
-----------------------------------------
Example without PXE for a)
-----------------------------------------
* NIC
15:43:27.390642 192.168.128.12.bootpc > dhcpsrv.vdi.test.bootps: [udp
sum ok] BOOTP/DHCP, Request from 42:b1:60:11:23:12 (oui Unknown),
length 260, hops 1,
xid 0x574fe450, Flags [none]
Gateway-IP 192.168.128.12
Client-Ethernet-Address 42:b1:60:11:23:12 (oui Unknown)
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message Option 53, length 1: Discover
Client-ID Option 61, length 7: ether 42:b1:60:11:23:12
Parameter-Request Option 55, length 5:
Subnet-Mask, Default-Gateway, Domain-Name-Server, Domain-Name
Server-ID
END Option 255, length 0
15:43:27.391136 IP dhcpsrv.vdi.test.bootps > 192.168.128.12.bootps:
[udp sum ok] BOOTP/DHCP, Reply, length 300, hops 1,
xid 0x574fe450, Flags [none]
Your-IP 192.168.129.215
Gateway-IP 192.168.128.12
Client-Ethernet-Address 42:b1:60:11:23:12 (oui Unknown)
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message Option 53, length 1: Offer
Server-ID Option 54, length 4: dhcpsrv.vdi.test
Lease-Time Option 51, length 4: 360
Subnet-Mask Option 1, length 4: 255.255.255.0
Default-Gateway Option 3, length 4: 192.168.129.1
Domain-Name-Server Option 6, length 8: dns01.vdi.test,dns02.vdi.test
Domain-Name Option 15, length 11: "d.vdi.test."
END Option 255, length 0
PAD Option 0, length 0, occurs 9
**** WINDOWS OS Stack ****
15:46:42.656691 192.168.128.12.bootpc > dhcpsrv.vdi.test.bootps:
[udp sum ok] BOOTP/DHCP, Request from 42:b1:60:11:23:12 (oui Unknown),
length 300, hops 1,
xid 0x42f613d, secs 768, Flags [Broadcast]
Gateway-IP 192.168.128.12
Client-Ethernet-Address 42:b1:60:11:23:12 (oui Unknown)
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message Option 53, length 1: Discover
CLASS Option 77, length 7: "vditest"
Client-ID Option 61, length 7: ether 42:b1:60:11:23:12
Hostname Option 12, length 11: "pvs-pd-t-04"
Vendor-Class Option 60, length 8: "MSFT 5.0"
Parameter-Request Option 55, length 12:
Subnet-Mask, Domain-Name, Default-Gateway, Domain-Name-Server
Netbios-Name-Server, Netbios-Node, Netbios-Scope, Router-Discovery
Static-Route, Classless-Static-Route,
Classless-Static-Route-Microsoft, Vendor-Option
END Option 255, length 0
PAD Option 0, length 0
15:46:43.658587 dhcpsrv.vdi.test.bootps > 192.168.128.12.bootps: [udp
sum ok] BOOTP/DHCP, Reply, length 300, hops 1,
xid 0x42f613d, secs 768, Flags [Broadcast]
Your-IP 192.168.129.184
Gateway-IP 192.168.128.12
Client-Ethernet-Address 42:b1:60:11:23:12 (oui Unknown)
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message Option 53, length 1: Offer
Server-ID Option 54, length 4: dhcpsrv.vdi.test
Lease-Time Option 51, length 4: 3600
Subnet-Mask Option 1, length 4: 255.255.255.0
Domain-Name Option 15, length 11: "d.vdi.test."
Default-Gateway Option 3, length 4: 192.168.129.1
Domain-Name-Server Option 6, length 8: dns01.vdi.test,dns02.vdi.test
END Option 255, length 0
PAD Option 0, length 0, occurs 9
-----------------------------------------
Example with PXE for b)
-----------------------------------------
**** NIC ****
16:09:23.366919 192.168.128.12.bootps > dhcpsrv.vdi.test.bootps: [udp
sum ok] BOOTP/DHCP, Request from d6:12:16:ef:ab:32 (oui Unknown),
length 384, hops 2,
xid 0x16dae42a, secs 4, Flags [none] (0x0000)
Gateway-IP 192.168.128.12
Client-Ethernet-Address d6:12:16:ef:ab:32 (oui Unknown)
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message Option 53, length 1: Discover
MSZ Option 57, length 2: 1260
ARCH Option 93, length 2: 0
NDI Option 94, length 3: 1.2.1
Vendor-Class Option 60, length 32:
"PXEClient:Arch:00000:UNDI:002001"
CLASS Option 77, length 4: "gPXE"
Parameter-Request Option 55, length 13:
Subnet-Mask, Default-Gateway, Domain-Name-Server, LOG
Hostname, Domain-Name, RP, Vendor-Option
Vendor-Class, TFTP, BF, Option 175
Option 203
T175 Option 175, length 42:
45317,272,60545,14616,257,8705,281,257,8449,272,258,4609,275,257,4353,491,769,0,5889,277,257
Client-ID Option 61, length 7: ether d6:12:16:ef:ab:32
GUID Option 97, length 17:
0.76.160.173.120.214.79.202.71.138.35.67.120.117.143.246.52
END Option 255, length 0
16:09:24.367470 dhcpsrv.vdi.test.bootps > 192.168.128.12.bootps: [udp
sum ok] BOOTP/DHCP, Reply, length 300, hops 2,
xid 0x16dae42a, secs 4, Flags [none] (0x0000)
Your-IP 192.168.129.34
Gateway-IP 192.168.128.12
Client-Ethernet-Address d6:12:16:ef:ab:32 (oui Unknown)
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message Option 53, length 1: Offer
Server-ID Option 54, length 4: dhcpsrv.vdi.test
Lease-Time Option 51, length 4: 360
Subnet-Mask Option 1, length 4: 255.255.255.0
Default-Gateway Option 3, length 4: 192.168.129.1
Domain-Name-Server Option 6, length 8: dns01.vdi.test,dns02.vdi.test
Domain-Name Option 15, length 11: "d.vdi.test."
END Option 255, length 0
PAD Option 0, length 0, occurs 9
**** WINDOWS OS Stack ****
16:10:05.079842 192.168.128.12.bootps > dhcpsrv.vdi.test.bootps: [udp
sum ok] BOOTP/DHCP, Request from d6:12:16:ef:ab:32 (oui Unknown),
length 300, hops 2,
xid 0x5ba369f0, Flags [Broadcast] (0x8000)
Gateway-IP 192.168.128.12
Client-Ethernet-Address d6:12:16:ef:ab:32 (oui Unknown)
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message Option 53, length 1: Discover
CLASS Option 77, length 5: "vdipc"
Client-ID Option 61, length 7: ether d6:12:16:ef:ab:32
Hostname Option 12, length 12: "vdisk-04-002"
Vendor-Class Option 60, length 8: "MSFT 5.0"
Parameter-Request Option 55, length 12:
Subnet-Mask, Domain-Name, Default-Gateway, Domain-Name-Server
Netbios-Name-Server, Netbios-Node, Netbios-Scope, Router-Discovery
Static-Route, Classless-Static-Route,
Classless-Static-Route-Microsoft, Vendor-Option
END Option 255, length 0
PAD Option 0, length 0, occurs 2
16:10:05.080139 dhcpsrv.vdi.test.bootps > 192.168.128.12.bootps: [udp
sum ok] BOOTP/DHCP, Reply, length 300, hops 2,
xid 0x5ba369f0, Flags [Broadcast] (0x8000)
Your-IP 192.168.129.34
Gateway-IP 192.168.128.12
Client-Ethernet-Address d6:12:16:ef:ab:32 (oui Unknown)
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message Option 53, length 1: Offer
Server-ID Option 54, length 4: dhcpsrv.vdi.test
Lease-Time Option 51, length 4: 3600
Subnet-Mask Option 1, length 4: 255.255.255.0
Domain-Name Option 15, length 11: "d.vdi.test."
Default-Gateway Option 3, length 4: 192.168.129.1
Domain-Name-Server Option 6, length 8: dns01.vdi.test,dns02.vdi.test
END Option 255, length 0
PAD Option 0, length 0, occurs 9
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