Network Topology
independent DHCP server -- leaf -- border -- dhcp relay-- dhcp client
Problem Description
the dhcp client and relay sent out a dhcp discover packet and the DHCP server didn"t receive it. So dhcp process fail even we disable dhcp sserver and dhcp to the controller for this private network in ADDC.
Process Analysis
the dhcp discover will send to the border and border will forward it via flow-table or routing-table.
And the Border have this default flow-table:
Flow entry 4 information:
COOKIE: 0x2c324757415057, priority: 61000, hard time: 0, idle time: 0, flags:
flow_send_rem, byte count: 25415600, packet count: 76215
Create time:18:12:35 07/26/2023, Last modified time:18:12:35 07/26/2023
Match information:
Ethernet type: 0x0800
IP protocol: 17
UDP source port: 68, mask: 0xffff
UDP destination port: 67, mask: 0xffff
Experimenter:
FlowFlag: 0x6
Instruction information:
Write actions:
Output interface: Controller, send length: 65509 bytes
And the Border have this high priority flow-table for a private network:
Flow entry 12 information:
COOKIE: 0x2c324757415057, priority: 61500, hard time: 0, idle time: 0, flags:
flow_send_rem, byte count: 4550, packet count: 13
Create time:15:48:43 09/20/2023, Last modified time:15:48:43 09/20/2023
Match information:
Ethernet type: 0x0800
IP protocol: 17
UDP source port: 68, mask: 0xffff
UDP destination port: 67, mask: 0xffff
Tunnel ID: 1095, mask: 0xffffffffffffffff
Experimenter:
FlowFlag: 0x4
Instruction information:
Write actions:
Output interface: Normal
but the port which this traffic in is a normal route port and this traffic will not match a tunnel id in the detail flow-table, and will match the default flow-table.
Solution
Enable the dhcp to controller for all the private networks which need the ADDC contoller act as a dhcp server.
and the addc will deploy a flow-table for it:
Flow entry 12 information:
COOKIE: 0x2c324757415057, priority: 61500, hard time: 0, idle time: 0, flags:
flow_send_rem, byte count: 4550, packet count: 13
Create time:15:48:43 09/20/2023, Last modified time:15:48:43 09/20/2023
Match information:
Ethernet type: 0x0800
IP protocol: 17
UDP source port: 68, mask: 0xffff
UDP destination port: 67, mask: 0xffff
Tunnel ID: 1094, mask: 0xffffffffffffffff
Experimenter:
FlowFlag: 0x4
Instruction information:
Write actions:
Output interface: Controller, send length: 65509 bytes #packet send to contoller.
And disable the dhcp to contoller under the Fabric. ADDC will delete the default flow-table for DHCP, and if A dhcp discover packet don"t match the specified private network flow-table, it will be forward via the routing-table
T