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Subject: [ActiveDir] [OT] DHCP Relay

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ifconfig

Posts:49

03/15/2010 8:04 PM
Begging your collective pardons for this OT question. I've setup a superscope to provide addressing capabilities to two subnets separated by a firewall thusly: [subnet A] <-----> (fwIPA) [Firewall] (fwIPB)(fwIPC) <------> DHCP server in subnetB Subnet A is 192.0.0.0/24 fwIPA is the gateway IP address on the subnet A side and is 192.0.0.1--This subnet is where the DHCP client is located. fwIPB is the gateway IP address on the subnetB side of the firewall is 10.0.0.1--This subnet is where the DHCP server is located with IP address 10.0.0.2 Special note: the firewall also has fwIPC which is 163.0.0.1, its default IP address. It all works via routing, but as I'm not the networking expert, I can't explain. The firewall's been setup to relay DHCP from subnetA to subnetB. The firewall's DHCP relay agent has been setup to forward requests to the DHCP server in subnetB The problem: I see packets arriving on the interface to the DHCP server in subnetB (DHCPDISCOVER) but nothing going back. In other words, the DHCP never sends an offer back. The contents of the packet are: Frame 124 (342 bytes on wire, 342 bytes captured) Ethernet II, Src: Cisco_a3:a0:3f (00:12:da:a3:a0:3f), Dst: Vmware_9a:2c:f3 (00:0c:29:9a:2c:f3) Internet Protocol, Src: 163.0.0.1 (fwIPC), Dst: 10.0.0.2 (DHCP Server) User Datagram Protocol, Src Port: bootps (67), Dst Port: bootps (67) Bootstrap Protocol Message type: Boot Request (1) Hardware type: Ethernet Hardware address length: 6 Hops: 1 Transaction ID: 0xbda66acf 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: 192.0.0.1 (fwIPA) Client MAC address: Dell_cd:37:5d (00:24:e8:cd:37:5d) Client hardware address padding: 00000000000000000000 Server host name not given Boot file name not given Magic cookie: (OK) Option: (t=53,l=1) DHCP Message Type = DHCP Discover Option: (53) DHCP Message Type Length: 1 Value: 01 Option: (t=61,l=7) Client identifier Option: (61) Client identifier Length: 7 Value: 010024E8CD375D Hardware type: Ethernet Client MAC address: Dell_cd:37:5d (00:24:e8:cd:37:5d) Option: (t=12,l=10) Host Name = "ADM08MC" Option: (12) Host Name Length: 10 Value: 41444D3038534C414952 Option: (t=60,l=8) Vendor class identifier = "MSFT 5.0" Option: (60) Vendor class identifier Length: 8 Value: 4D53465420352E30 Option: (t=55,l=12) Parameter Request List Option: (55) Parameter Request List Length: 12 Value: 010F03062C2E2F1F2179F92B 1 = Subnet Mask 15 = Domain Name 3 = Router 6 = Domain Name Server 44 = NetBIOS over TCP/IP Name Server 46 = NetBIOS over TCP/IP Node Type 47 = NetBIOS over TCP/IP Scope 31 = Perform Router Discover 33 = Static Route 121 = Classless Static Route 249 = Private/Classless Static Route I hope this makes sense. My question is, does the firewall (fwIPC address) have to connect to the DHCP server with fwIPA so that the server can respond or is it simply sufficient to have the relay agent IP address in the packet? If this doesn't make sense, can you tell me what your setup is, with IP addresses for the relay agent, the DHCP server, etc.? Please feel free to substitute any IP address you choose, I'd like to simply see what the setup is in general. Thanks a bunch.

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