Re: R/S giaddr

!
ip dhcp excluded-address 10.10.1.1 10.10.1.10
!
ip dhcp pool OK
   network 10.10.1.0 255.255.255.0
   domain-name ccie.net
   default-router 10.10.1.1
   lease 0 0 10
!

2012/3/28 Israel Ogongo <ohio38jr_at_gmail.com>:
> Hi,
>
> Perhaps you would want to post your config on the DHCP router?
>
>
> On Wed, Mar 28, 2012 at 11:56 AM, Hasse <eriksson.hans_at_gmail.com> wrote:
>>
>> Topology:
>> R1-DHCP-Server------SW1---------SW2-------R3-CLIENT
>> |
>> R2-Client
>>
>> R1 DHCP Server connected to SW1
>> R2 DHCP Client connected to SW1
>> R3 DHCP Client Connected to SW2
>> SW1 and SW2 dot1q trunk
>> Vlan 10 on all
>>
>> Question 1:
>> Where or when does DHCP snooping interrupt and write to the Snooping DB?
>> Does Snooping place a place holder in the DB when the switch see the
>> DHCPREG?
>> and writing the DB when seeing the ACK?
>>
>> Question 2:
>>
>> When using a cisco router as a DHCP server in my case R1 connected to
>> SW1 and Client R2.
>> I recive the following error:
>> *Mar 28 07:37:53.462: DHCPD: inconsistent relay information.
>> *Mar 28 07:37:53.462: DHCPD: relay information option exists, but
>> giaddr is zero.
>> Why?
>> My options are as follow
>>
>> 1) Turn off option 82 on the switch
>> (no ip dhcp snooping information option)
>> 2) On the DHCP server R1
>> (ip dhcp relay information trusted)
>> 3) ?
>> 4) ?
>>
>> Question 3:
>> I do not understand this problem fully, about giaddr.
>>
>>
>> This server and Client are sitting on the same subnet. That is why I
>> get the error. According to RFC I should be able to use following.
>>
>> The server SHOULD select the IP address the server is using for
>> communication on that subnet as the 'server identifier'.
>>
>> Giaddr = Relay agent ip address used in booting via a relay agent.
>>
>> Giaddr from RFC 2131
>>
>>
>> If 'giaddr' is 0x0 in the DHCPREQUEST message, the client is on
>> the same subnet as the server. The server MUST
>> broadcast the DHCPNAK message to the 0xffffffff broadcast address
>> because the client may not have a correct network address or subnet
>> mask, and the client may not be answering ARP requests.
>> Otherwise, the server MUST send the DHCPNAK message to the IP
>> address of the BOOTP relay agent, as recorded in 'giaddr'. The
>> relay agent will, in turn, forward the message directly to the
>> client's hardware address, so that the DHCPNAK can be delivered even
>> if the client has moved to a new network.
>>
>>
>> The 'server identifier' field is used both to identify a DHCP server
>> in a DHCP message and as a destination address from clients to
>> servers. A server with multiple network addresses MUST be prepared
>> to to accept any of its network addresses as identifying that server
>> in a DHCP message. To accommodate potentially incomplete network
>> connectivity, a server MUST choose an address as a 'server
>> identifier' that, to the best of the server's knowledge, is reachable
>> from the client. For example, if the DHCP server and the DHCP client
>> are connected to the same subnet (i.e., the 'giaddr' field in the
>> message from the client is zero), the server SHOULD select the IP
>> address the server is using for communication on that subnet as the
>> 'server identifier'. If the server is using multiple IP addresses on
>> that subnet, any such address may be used. If the server has
>> received a message through a DHCP relay agent, the server SHOULD
>> choose an address from the interface on which the message was
>> recieved as the 'server identifier' (unless the server has other,
>> better information on which to make its choice). DHCP clients MUST
>> use the IP address provided in the 'server identifier' option for any
>> unicast requests to the DHCP server.
>>
>> DHCP messages broadcast by a client prior to that client obtaining
>> its IP address must have the source address field in the IP header
>> set to 0.
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> On R1 DHCP Server
>>
>> *Mar 28 07:37:57.462: DHCPD: inconsistent relay information.
>> *Mar 28 07:37:57.462: DHCPD: relay information option exists, but
>> giaddr is zero.
>> *Mar 28 07:38:15.462: DHCPD: inconsistent relay information.
>> *Mar 28 07:38:15.462: DHCPD: relay information option exists, but
>> giaddr is zero.
>> *Mar 28 07:38:18.462: DHCPD: inconsistent relay information.
>> *Mar 28 07:38:18.462: DHCPD: relay information option exists, but
>> giaddr is zero.
>> *Mar 28 07:38:22.462: DHCPD: inconsistent relay information.
>> *Mar 28 07:38:22.462: DHCPD: relay information option exists, but
>> giaddr is zero.
>>
>> On Switch1
>> 0x52 0x12 0x1 0x6 0x0 0x4 0x0 0xA 0x1 0x4 0x2 0x8 0x0 0x6 0x0 0x1A
>> 0xE3 0x31 0xF 0x0
>> *Mar 6 15:13:28.826: DHCP_SNOOPING_SW: bridge packet get invalid mat
>> entry: FFFF.FFFF.FFFF, packet
>> is flooded to ingress VLAN: (10)
>> *Mar 6 15:13:32.358: DHCPSNOOP(hlfm_set_if_input): Setting if_input
>> to Fa1/0/2 for pak. Was not set
>> *Mar 6 15:13:32.358: DHCPSNOOP(hlfm_set_if_input): Clearing if_input
>> for pak. Was Fa1/0/2
>> *Mar 6 15:13:32.358: DHCPSNOOP(hlfm_set_if_input): Setting if_input
>> to Fa1/0/2 for pak. Was not set
>> *Mar 6 15:13:32.358: DHCP_SNOOPING: received new DHCP packet from
>> input interface (FastEthernet1/0/2)
>> *Mar 6 15:13:32.366: DHCP_SNOOPING: process new DHCP packet, message
>> type: DHCPDISCOVER, input interface: Fa1/0/2, MAC da: ffff.ffff.ffff,
>> MAC sa: 001d.46d1.fc68, IP da: 255.255.255.255, IP sa: 0.0.0.0, DHCP
>> ciaddr: 0.0.0.0, DHCP yiaddr: 0.0.0.0, DHCP siaddr: 0.0.0.0, DHCP
>> giaddr: 0.0.0.0, DHCP chaddr: 001d.46d1.fc68
>> *Mar 6 15:13:32.366: DHCP_SNOOPING: add relay information option.
>> *Mar 6 15:13:32.366: DHCP_SNOOPING_SW: Encoding opt82 CID in
>> vlan-mod-port format
>> *Mar 6 15:13:32.366: DHCP_SNOOPING_SW: Encoding opt82 RID in MAC address
>> format
>> *Mar 6 15:13:32.366: DHCP_SNOOPING: binary dump of relay info option,
>> length: 20 data:
>> 0x52 0x12 0x1 0x6 0x0 0x4 0x0 0xA 0x1 0x4 0x2 0x8 0x0 0x6 0x0 0x1A
>> 0xE3 0x31 0xF 0x0
>> *Mar 6 15:13:32.366: DHCP_SNOOPING_SW: bridge packet get invalid mat
>> entry: FFFF.FFFF.FFFF, packet is flooded to ingress VLAN: (10)
>> *Mar 6 15:13:36.359: DHCPSNOOP(hlfm_set_if_input): Setting if_input
>> to Fa1/0/2 for pak. Was not set
>> *Mar 6 15:13:36.359: DHCPSNOOP(hlfm_set_if_input): Clearing if_input
>> for pak. Was Fa1/0/2
>> *Mar 6 15:13:36.359: DHCPSNOOP(hlfm_set_if_input): Setting if_input
>> to Fa1/0/2 for pak. Was not set
>> *Mar 6 15:13:36.359: DHCP_SNOOPING: received new DHCP packet from
>> input interface (FastEthernet1/0/2)
>> *Mar 6 15:13:36.359: DHCP_SNOOPING: process new DHCP packet, message
>> type: DHCPDISCOVER, input interfac
>>
>>
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Received on Wed Mar 28 2012 - 14:15:56 ART