Subject: Re: how to use/find relay agent information - msg#00284

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Re: how to use/find relay agent information

*** From dhcp-server -- To unsubscribe, see the end of this message. *** On Sat, May 24, 2003 at 12:20:31AM +1000, Glenn Satchell wrote: > > > Date: Fri, 23 May 2003 15:52:27 +0200 > > From: Arni Ingimundarson <arning@xxxxxxxxxxxxxxxxxxxxxx> > > > > Hello, > > > > On Tue, May 20, 2003 at 10:02:20AM +1000, Glenn Satchell wrote: > > > > > > The relay agent fills in the giaddr field with the address of the > > > interface where the dhcpdiscover was received. This is automatically > > > decoded by the dhcp server so that it knows which subnet the request > > > came from originally. You only need specify all the subnets and a > > > suitable range in each. > > > > I did this and it didn't work, the server offered to a client from the > > last subnet an address from the first subnet (see dhcpd.conf and log > > file at the end of this mail). > > > > Any hints appreciated. > > Unless all your subnets are shared on the same physical network segment > remove the shared-network statement. This statement tells the dhcp > server that all the subnets are on the same physical segment, therefore > the dhcp server can assign an address from any range in the > shared-network to those clients. All the subnets share (indirectly) the same interface, so I do need the shared network statement. DHCP requests from subnets other than the one physicly connected to the server get forwarded by the router. All subnets are connected to this router. Best regards, Arni > regards, > -glenn > > > Best regards, > > Arni > > > > > > > regards, > > > -glenn > > > > > > > From: Arni Ingimundarson <arning@xxxxxxxxxxxxxxxxxxxxxx> > > > > To: dhcp-server@xxxxxxx > > > > Subject: how to use/find relay agent information > > > > > > > > Hello, > > > > > > > > I am in the process of upgrading our DHCP server to version 3.0.1 > > > > (rc11 for now). > > > > > > > > We have a big network with 10 subnets and about 6-700 users (its a big > > > > student home). Each room has a fixed IP Address and we went with DHCP > > > > with a fixed MAC <--> IP relation to ease configuration for the users. > > > > > > > > To reduce the work on collecting the MAC-Addresses from each user I > > > > want to have a small pool of addresses for unknown MACs but I need to > > > > know on wich subnet the discover request came from. > > > > > > > > I know I can use the agent.circuit-id option but I dont know exactly > > > > what ID the cisco router we have uses. Is there a way to find out > > > > what circuit-id the router uses when relaying DHCP requests ? > > > > > > > > > > > > Any help would be much appreciated. > > > > > > > > Best regards, > > > > Arni > > > > > > My config file looks like this: > > > > # dhcpd.con ################################ > > # Globals # > > option domain-name "karlshof.wh.tu-darmstadt.de"; > > option subnet-mask 255.255.255.128; > > option domain-name-servers 130.83.218.222, 130.83.219.101, > > > > shared-network KARLSHOF { > > > > # Subnet 1 > > Subnet 130.83.217.128 netmask 255.255.255.128 { > > option routers 130.83.217.254; > > option broadcast-address 130.83.217.255; > > > > # > > # it didn't matter if the range statement > > # was in a pool or not (I tried both) > > # > > pool { > > default-lease-time 120; > > max-lease-time 240; > > range 130.83.217.230 130.83.217.239; > > allow unknown clients; > > } > > > > > > host C5107 { > > fixed-address 130.83.217.135; > > hardware ethernet 00:10:5A:97:BB:10; > > option host-name "Bicker"; > > } > > > > # Subnet 2 > > Subnet 130.83.218.0 netmask 255.255.255.128 { > > #subnet options > > } > > . > > . > > . > > # Subnet 7 > > Subnet 130.83.220.128 netmask 255.255.255.128 { > > #subnet options > > } > > > > # End of Configfile ############################# > > > > > > from /var/log/daemon.log > > > > May 23 14:57:01 nameholder dhcpd: DHCPDISCOVER from 00:20:ed:37:63:04 > > via 130.83.220.254 > > May 23 14:57:01 nameholder dhcpd: DHCPOFFER on 130.83.217.239 to > > 00:20:ed:37:63:04 (HALUX) via 130.83.220.254 > > May 23 14:57:03 nameholder dhcpd: DHCPDISCOVER from 00:20:ed:37:63:04 > > (HALUX) via 130.83.220.254 > > May 23 14:57:03 nameholder dhcpd: DHCPOFFER on 130.83.217.239 to > > 00:20:ed:37:63:04 (HALUX) via 130.83.220.254 > > May 23 14:57:11 nameholder dhcpd: DHCPDISCOVER from 00:20:ed:37:63:04 > > (HALUX) via 130.83.220.254 > > May 23 14:57:11 nameholder dhcpd: DHCPOFFER on 130.83.217.239 to > > 00:20:ed:37:63:04 (HALUX) via 130.83.220.254 > > > > > > > > ----------------------------------------------------------------------- > > List Archives : http://www.isc.org/ml-archives/dhcp-server/ > > Unsubscribe : http://www.isc.org/dhcp-lists.html > > -or- : mailto:dhcp-server-request@xxxxxxx?Subject=unsubscribe > > ----------------------------------------------------------------------- > > > > > ----------------------------------------------------------------------- > List Archives : http://www.isc.org/ml-archives/dhcp-server/ > Unsubscribe : http://www.isc.org/dhcp-lists.html > -or- : mailto:dhcp-server-request@xxxxxxx?Subject=unsubscribe > ----------------------------------------------------------------------- ----------------------------------------------------------------------- List Archives : http://www.isc.org/ml-archives/dhcp-server/ Unsubscribe : http://www.isc.org/dhcp-lists.html -or- : mailto:dhcp-server-request@xxxxxxx?Subject=unsubscribe -----------------------------------------------------------------------

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Re: how to use/find relay agent information

*** From dhcp-server -- To unsubscribe, see the end of this message. *** > All the subnets share (indirectly) the same interface, so I do need > the shared network statement. DHCP requests from subnets other than > the one physicly connected to the server get forwarded by the router. > All subnets are connected to this router. That is not what a "shared network" statement implies. Stating that your networks are shared is telling the server that they are part of a single broadcast domain. Since the initial DISCOVER request is broadcast by a system that does not yet have an IP address, your router would not be able to tell which subnet it is supposed to be on. It uses a single relay address (the primary) for all requests. The DHCP server then maps the relay address to a broadcast domain (physical network or VLAN) and hence to a set of address pools. Since you have your various subnets on separate router interfaces or VLANs, the router is putting in different relay addresses for each subnet, Remove the shared network statement. It is telling your DHCP server that all of your relay addresses are equivalent since they are all part of a single large network. -- Bruce A. Hudson | Bruce.Hudson@xxxxxx UCIS, Networks and Systems | Dalhousie University | Halifax, Nova Scotia, Canada | (902) 494-3405 ----------------------------------------------------------------------- List Archives : http://www.isc.org/ml-archives/dhcp-server/ Unsubscribe : http://www.isc.org/dhcp-lists.html -or- : mailto:dhcp-server-request@xxxxxxx?Subject=unsubscribe -----------------------------------------------------------------------

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Re: how to use/find relay agent information

*** From dhcp-server -- To unsubscribe, see the end of this message. *** On Sat, May 24, 2003 at 12:20:31AM +1000, Glenn Satchell wrote: > > > Date: Fri, 23 May 2003 15:52:27 +0200 > > From: Arni Ingimundarson <arning@xxxxxxxxxxxxxxxxxxxxxx> > > > > Hello, > > > > On Tue, May 20, 2003 at 10:02:20AM +1000, Glenn Satchell wrote: > > > > > > The relay agent fills in the giaddr field with the address of the > > > interface where the dhcpdiscover was received. This is automatically > > > decoded by the dhcp server so that it knows which subnet the request > > > came from originally. You only need specify all the subnets and a > > > suitable range in each. > > > > I did this and it didn't work, the server offered to a client from the > > last subnet an address from the first subnet (see dhcpd.conf and log > > file at the end of this mail). > > > > Any hints appreciated. > > Unless all your subnets are shared on the same physical network segment > remove the shared-network statement. This statement tells the dhcp > server that all the subnets are on the same physical segment, therefore > the dhcp server can assign an address from any range in the > shared-network to those clients. All the subnets share (indirectly) the same interface, so I do need the shared network statement. DHCP requests from subnets other than the one physicly connected to the server get forwarded by the router. All subnets are connected to this router. Best regards, Arni > regards, > -glenn > > > Best regards, > > Arni > > > > > > > regards, > > > -glenn > > > > > > > From: Arni Ingimundarson <arning@xxxxxxxxxxxxxxxxxxxxxx> > > > > To: dhcp-server@xxxxxxx > > > > Subject: how to use/find relay agent information > > > > > > > > Hello, > > > > > > > > I am in the process of upgrading our DHCP server to version 3.0.1 > > > > (rc11 for now). > > > > > > > > We have a big network with 10 subnets and about 6-700 users (its a big > > > > student home). Each room has a fixed IP Address and we went with DHCP > > > > with a fixed MAC <--> IP relation to ease configuration for the users. > > > > > > > > To reduce the work on collecting the MAC-Addresses from each user I > > > > want to have a small pool of addresses for unknown MACs but I need to > > > > know on wich subnet the discover request came from. > > > > > > > > I know I can use the agent.circuit-id option but I dont know exactly > > > > what ID the cisco router we have uses. Is there a way to find out > > > > what circuit-id the router uses when relaying DHCP requests ? > > > > > > > > > > > > Any help would be much appreciated. > > > > > > > > Best regards, > > > > Arni > > > > > > My config file looks like this: > > > > # dhcpd.con ################################ > > # Globals # > > option domain-name "karlshof.wh.tu-darmstadt.de"; > > option subnet-mask 255.255.255.128; > > option domain-name-servers 130.83.218.222, 130.83.219.101, > > > > shared-network KARLSHOF { > > > > # Subnet 1 > > Subnet 130.83.217.128 netmask 255.255.255.128 { > > option routers 130.83.217.254; > > option broadcast-address 130.83.217.255; > > > > # > > # it didn't matter if the range statement > > # was in a pool or not (I tried both) > > # > > pool { > > default-lease-time 120; > > max-lease-time 240; > > range 130.83.217.230 130.83.217.239; > > allow unknown clients; > > } > > > > > > host C5107 { > > fixed-address 130.83.217.135; > > hardware ethernet 00:10:5A:97:BB:10; > > option host-name "Bicker"; > > } > > > > # Subnet 2 > > Subnet 130.83.218.0 netmask 255.255.255.128 { > > #subnet options > > } > > . > > . > > . > > # Subnet 7 > > Subnet 130.83.220.128 netmask 255.255.255.128 { > > #subnet options > > } > > > > # End of Configfile ############################# > > > > > > from /var/log/daemon.log > > > > May 23 14:57:01 nameholder dhcpd: DHCPDISCOVER from 00:20:ed:37:63:04 > > via 130.83.220.254 > > May 23 14:57:01 nameholder dhcpd: DHCPOFFER on 130.83.217.239 to > > 00:20:ed:37:63:04 (HALUX) via 130.83.220.254 > > May 23 14:57:03 nameholder dhcpd: DHCPDISCOVER from 00:20:ed:37:63:04 > > (HALUX) via 130.83.220.254 > > May 23 14:57:03 nameholder dhcpd: DHCPOFFER on 130.83.217.239 to > > 00:20:ed:37:63:04 (HALUX) via 130.83.220.254 > > May 23 14:57:11 nameholder dhcpd: DHCPDISCOVER from 00:20:ed:37:63:04 > > (HALUX) via 130.83.220.254 > > May 23 14:57:11 nameholder dhcpd: DHCPOFFER on 130.83.217.239 to > > 00:20:ed:37:63:04 (HALUX) via 130.83.220.254 > > > > > > > > ----------------------------------------------------------------------- > > List Archives : http://www.isc.org/ml-archives/dhcp-server/ > > Unsubscribe : http://www.isc.org/dhcp-lists.html > > -or- : mailto:dhcp-server-request@xxxxxxx?Subject=unsubscribe > > ----------------------------------------------------------------------- > > > > > ----------------------------------------------------------------------- > List Archives : http://www.isc.org/ml-archives/dhcp-server/ > Unsubscribe : http://www.isc.org/dhcp-lists.html > -or- : mailto:dhcp-server-request@xxxxxxx?Subject=unsubscribe > ----------------------------------------------------------------------- ----------------------------------------------------------------------- List Archives : http://www.isc.org/ml-archives/dhcp-server/ Unsubscribe : http://www.isc.org/dhcp-lists.html -or- : mailto:dhcp-server-request@xxxxxxx?Subject=unsubscribe -----------------------------------------------------------------------

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Re: how to use/find relay agent information

*** From dhcp-server -- To unsubscribe, see the end of this message. *** > All the subnets share (indirectly) the same interface, so I do need > the shared network statement. DHCP requests from subnets other than > the one physicly connected to the server get forwarded by the router. > All subnets are connected to this router. That is not what a "shared network" statement implies. Stating that your networks are shared is telling the server that they are part of a single broadcast domain. Since the initial DISCOVER request is broadcast by a system that does not yet have an IP address, your router would not be able to tell which subnet it is supposed to be on. It uses a single relay address (the primary) for all requests. The DHCP server then maps the relay address to a broadcast domain (physical network or VLAN) and hence to a set of address pools. Since you have your various subnets on separate router interfaces or VLANs, the router is putting in different relay addresses for each subnet, Remove the shared network statement. It is telling your DHCP server that all of your relay addresses are equivalent since they are all part of a single large network. -- Bruce A. Hudson | Bruce.Hudson@xxxxxx UCIS, Networks and Systems | Dalhousie University | Halifax, Nova Scotia, Canada | (902) 494-3405 ----------------------------------------------------------------------- List Archives : http://www.isc.org/ml-archives/dhcp-server/ Unsubscribe : http://www.isc.org/dhcp-lists.html -or- : mailto:dhcp-server-request@xxxxxxx?Subject=unsubscribe -----------------------------------------------------------------------