Yes, I did notice that. I was a bit surprised to see it request its old IP address, but I had heard that Windows does that. It was running Windows 98.
By the way, this was a lab network and I really shouldn't have used network 36.0.0.0 which is Stanford's IP address I think. Please ignore it! ;-) Priscilla At 08:01 PM 10/5/01, Leigh Anne Chisholm wrote: >Priscilla, I'm wondering if you caught part of your trace? Specifically >this part: > > Requested IP AddressDHCP Option > Option Code: 50 Requested IP Address > Option Length: 4 > Address: 36.1.1.2 > >It's not common knowledge that DHCP has an option to request the IP address >during the original IP address request used the last time the end-host was >on the network. Microsoft's implementation definitely includes this. > >Just a bit of trivia... > > > -- Leigh Anne > > > -----Original Message----- > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of > > Priscilla Oppenheimer > > Sent: Friday, October 05, 2001 5:45 PM > > To: [EMAIL PROTECTED] > > Subject: Re: DHCP communication [7:22272] > > > > > > You are in luck, sort of. In one of our previous tirades ;-) > > about DHCP, I > > sent the following message, which includes a DHCP Discover relayed by a > > router near the end. I can't send you the trace file, however, because it > > has some confidential stuff in it. > > > > > > Here's my config. The client is on the 36.1.1.0 network. > > > > I was sitting with my EtherPeek protocol analyzer on the > > 10.10.0.0 network. > > I could see the DHCP Discover come through to 10.10.0.1 as long as I used > > "ip helper-address 10.10.0.1." > > > > charlotte#s run > > Building configuration... > > > > Current configuration: > > ! > > version 11.0 > > service udp-small-servers > > service tcp-small-servers > > ! > > hostname charlotte > > ! > > enable password xxxx > > ! > > interface Ethernet0 > > ip address 10.10.0.2 255.255.255.0 > > ! > > interface Ethernet1 > > ip address 36.1.1.1 255.255.255.0 > > ip helper-address 10.10.0.1 > > ! > > interface Serial0 > > ip address 192.168.40.2 255.255.255.0 > > no fair-queue > > ! > > interface Serial1 > > no ip address > > shutdown > > ! > > interface TokenRing1 > > no ip address > > shutdown > > ! > > interface TokenRing0 > > no ip address > > shutdown > > ! > > router ospf 100 > > network 192.168.0.0 0.0.255.255 area 2 > > network 10.10.0.0 0.0.255.255 area 0 > > network 36.1.1.0 0.0.0.255 area 2 > > ! > > line con 0 > > line aux 0 > > transport input all > > line vty 0 4 > > password cisco > > login > > ! > > end > > > > > > The DHCP Discover from the client that I captured might be informative for > > people learning about how DHCP Relay works. Notice that the packet is a > > unicast, rather than a broadcast. Also, notice at the IP layer that the > > source address is the router, not the client's 0.0.0.0 address that you > > normally see with DHCP. The router also put its address in the DHCP server > > under "Gateway IP Address." The DHCP server needs to see this to > > know which > > subnet the client's request came from. > > > > Ethernet Header > > Destination: 00:00:0C:05:3E:80 > > Source: 00:00:0C:00:2E:75 > > Protocol Type:0x0800 IP > > IP Header - Internet Protocol Datagram > > Version: 4 > > Header Length: 5 (20 bytes) > > Type of Service: %00000000 > > Precedence: Routine, Normal Delay, Normal Throughput, Normal > > Reliability > > Total Length: 328 > > Identifier: 12800 > > Fragmentation Flags: %000 May Fragment Last Fragment > > Fragment Offset: 0 (0 bytes) > > Time To Live: 127 > > Protocol: 17 UDP > > Header Checksum: 0xD998 > > Source IP Address: 36.1.1.1 > > Dest. IP Address: 10.10.0.1 > > No IP Options > > UDP - User Datagram Protocol > > Source Port: 68 Bootstrap (BOOTP Client) > > Destination Port: 67 Bootstrap Protocol Server > > Length: 308 > > Checksum: 0x3159 > > BootP - Bootstrap Protocol > > Operation: 1 Boot Request > > Hardware Address Type: 1 Ethernet (10Mb) > > Hardware Address Length: 6 bytes > > Hops: 0 > > Transaction ID: 678970121 > > Seconds Since Boot Start: 0 > > Flags: 0x0000 > > IP Address Known By Client: 0.0.0.0 IP Address Not Known By Client > > Client IP Addr Given By Srvr: 0.0.0.0 > > Server IP Address: 0.0.0.0 > > Gateway IP Address: 36.1.1.1 > > Client Hardware Address: 00:E0:98:89:52:FA > > Unused: 0x00000000000000000000 > > Server Host Name: > > ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > > Boot File Name: > > ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > > DHCP - Dynamic Host Configuration Protocol > > DHCP Magic Cookie: 0x63825363 > > Message TypeDHCP Option > > Option Code: 53 Message Type > > Option Length: 1 > > Message Type: 1 Discover > > Client IdentifierDHCP Option > > Option Code: 61 Client Identifier > > Option Length: 7 > > Hardware Type: 1 > > Hardware Address: 00:E0:98:89:52:FA > > Requested IP AddressDHCP Option > > Option Code: 50 Requested IP Address > > Option Length: 4 > > Address: 36.1.1.2 > > Host Name AddressDHCP Option > > Option Code: 12 Host Name Address > > Option Length: 8 > > String: MACTEAM. > > Vendor Class IdentifierDHCP Option > > Option Code: 60 Vendor Class Identifier > > Option Length: 7 > > Option Data: > > MSFT 98 4D 53 46 54 20 39 38 > > Parameter Request ListDHCP Option > > Option Code: 55 Parameter Request List > > Option Length: 9 > > Requested Option: 1 Subnet Mask > > Requested Option: 15 Domain Name > > Requested Option: 3 Routers > > Requested Option: 6 Domain Name Servers > > Requested Option: 44 NetBIOS (TCP/IP) Name Servers > > Requested Option: 46 NetBIOS (TCP/IP) Node Type > > Requested Option: 47 NetBIOS (TCP/IP) Scope > > Requested Option: 43 Vendor Specific Information > > Requested Option: 77 User Class Information > > DHCP Option End > > Option Code: 255 End > > Extra bytes (Padding): > > ........... 00 00 00 00 00 00 00 00 00 00 00 > > Frame Check Sequence: 0x00000000 > > > > > > Priscilla > > > > > > At 05:44 PM 10/5/01, Lists Wizard wrote: > > >Hi Group, > > > > > >I am interested in the details (at the packet level) of DHCP > > communication > > >between the client and a DHCP server when there is a router in > > the middle. > > >Can any body provide me with sniffer trace of this kind of > > communication? I > > >use SnifferPro. > > > > > >Thanks > > > > > >Lists Wizard > > ________________________ > > > > Priscilla Oppenheimer > > http://www.priscilla.com ________________________ Priscilla Oppenheimer http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=22296&t=22272 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
