PCs Connected to an S9300 (DHCP Server) Obtain IP Addresses After a Long Delay

Publication Date:  2015-06-09 Views:  281 Downloads:  0
Issue Description
A PC is connected to an S9300. When the PC goes online for the first time, the PC quickly obtains an IP address. However, when the network cable connected to the PC is removed and reinstalled, the PC obtains an IP address after a one-minute delay.
Handling Process
1. Connect the PC to another DHCP server with the same network cable. The PC quickly obtains an IP address. Therefore, the network cable is normal.

2. Check CPCAR statistics on the S9300. No DHCP packet is discarded.

[Switch]display cpu-defend dhcp-client statistics all
CPCAR on slot 1
-------------------------------------------------------------------------------
Packet Type         Pass(Bytes)  Drop(Bytes)   Pass(Packets)   Drop(Packets)
dhcp-client            16773680            0           49335               0
-------------------------------------------------------------------------------
CPCAR on slot 2
-------------------------------------------------------------------------------
Packet Type         Pass(Bytes)  Drop(Bytes)   Pass(Packets)   Drop(Packets)
dhcp-client              169866            0             473               0
-------------------------------------------------------------------------------
[Switch]display cpu-defend dhcp-server statistics all
CPCAR on slot 1
-------------------------------------------------------------------------------
Packet Type         Pass(Bytes)  Drop(Bytes)   Pass(Packets)   Drop(Packets)
dhcp-server                   0            0               0               0
-------------------------------------------------------------------------------
CPCAR on slot 2
-------------------------------------------------------------------------------
Packet Type         Pass(Bytes)  Drop(Bytes)   Pass(Packets)   Drop(Packets)
dhcp-server                   0            0               0               0

3. Capture packets on the S9300. The S9300 does not return ACK packet after receiving a DHCP request packet. If a PC does not receive an ACK packets after sending three DHCP request packets, the PC waits for 30 seconds, and then sends a DHCP DISCOVER packet again to trigger the DHCP interaction process.

4. Enable DHCP debugging on the S9300. The S9300 does not correctly receive packets.

*0.69201741 HIQH-JHA-S9306 DHCP/7/INFO:
[STACK PKT]:    DHCP_Process_PktParse packet form OriginIfIndex = 84, slot = 2, port = 32
*0.69201742 HIQH-JHA-S9306 DHCP/7/INFO:
[STACK PKT]:    DHCP_Process_DhcpPkt Receive packet info:SRC/DST IF=GigabitEthernet2/0/32/GigabitEthernet2/0/32, VPN=0, SRC/DST MAC=0016-363c-ac53/3333-0001-0002, VLAN=21/0, VLAN_IF=23, SRC/DST IP=0.0.0.0/0.0.0.0, SRC/DST PORT=0/0, OP=0, GIADDR/Clientip/DhcpServerip/Requsetip=0.0.0.0/0.0.0.0/60.26.3.61/60.26.3.61(LEN=161)!

This problem has been rectified in V100R006C00SPC800. Upgrade the software to fix it.
Root Cause
1. Network quality is poor or network cable is loose.

2. Too many packets are sent to the CPU of the S9300, causing a delay to process DHCP packets.

3. The S9300 has a bug in software or hardware chip.
Suggestions
Upgrade the software version and install the latest patch.

END