Involved Products and Versions
S7700 V200R010
Networking
As shown in Figure 1-1, the S7706 functions as the core switch. A user uses the WOL server to send directed broadcast packets to dormant Samsung boxes to awaken them. There are about 170 Samsung boxes.
Figure 1-1 Networking diagram for the failure to awaken some Samsung boxes under a switch through WOL
Fault Symptom
When about 170 Samsung boxes are added to the same group, less than half of the boxes are awakened in batches and the boxes awakened are not fixed.
Cause Analysis
The default CPCAR value 64 kbit/s is used on the core switch S7706. When the S7706 receives a large number of directed broadcast packets (UDP packets) from the WOL server within a short period, the S7706 drops packets due to the rate limit.
Troubleshooting Procedure
Step 1 In the scenario where about 170 Samsung boxes are added to the same group, collect traffic statistics during the process of awakening the boxes from the dormant state.
l The WOL server sends 3040 directed broadcast packets. Ten packets with the UDP port being 7 and another ten packets with the UDP port being 9 are sent to the MAC address of each Samsung box at a time.
l The S5720HI connected to the WOL server receives 3040 packets and sends 3040 packets.
l The inbound interface Eth-Trunk12 of the core switch S7706 receives 3040 UDP packets. However, the outbound interface Eth-Trunk15 of the S7706 sends only 183 packets out.
<S7706> display
traffic policy statistics interface Eth-Trunk 12 inbound
Interface: Eth-Trunk12
Traffic policy inbound: a1
Rule number: 2
Current status: success
Statistics interval: 300
---------------------------------------------------------------------
Board : 1/1
---------------------------------------------------------------------
Matched
|
Packets:
3,020
|
Bytes:
459,040
|
Rate(pps):
0
|
Rate(bps):
0
---------------------------------------------------------------------
Passed
|
Packets:
3,020
|
Bytes:
459,040
|
Rate(pps):
0
|
Rate(bps):
0
---------------------------------------------------------------------
Dropped
|
Packets:
0
|
Bytes:
0
|
Rate(pps):
0
|
Rate(bps):
0
---------------------------------------------------------------------
Filter
|
Packets:
0
|
Bytes:
0
---------------------------------------------------------------------
Car
|
Packets:
0
|
Bytes:
0
---------------------------------------------------------------------
Board : 2/1
---------------------------------------------------------------------
Matched
|
Packets:
20
| Bytes: 3,040
|
Rate(pps):
0
|
Rate(bps):
0
---------------------------------------------------------------------
Passed
| Packets:
20
|
Bytes:
3,040
|
Rate(pps):
0
|
Rate(bps):
0
---------------------------------------------------------------------
Dropped
|
Packets:
0
|
Bytes:
0
|
Rate(pps):
0
| Rate(bps): 0
---------------------------------------------------------------------
Filter
|
Packets:
0
|
Bytes:
0
---------------------------------------------------------------------
Car
|
Packets:
0
|
Bytes:
0
---------------------------------------------------------------------
<S7706>
display traffic policy statistics interface Eth-Trunk 15 outbound
Interface: Eth-Trunk15
Traffic policy outbound: a1
Rule number: 2
Current status: success
Statistics interval: 300
---------------------------------------------------------------------
Board : 1/1
---------------------------------------------------------------------
Matched
|
Packets:
0
|
Bytes:
0
|
Rate(pps):
0
|
Rate(bps):
0
---------------------------------------------------------------------
Passed
|
Packets:
0
|
Bytes:
0
|
Rate(pps):
0
|
Rate(bps):
0
---------------------------------------------------------------------
Dropped
|
Packets:
0
|
Bytes:
0
|
Rate(pps):
0
|
Rate(bps):
0
---------------------------------------------------------------------
Filter
|
Packets:
0
|
Bytes:
0
---------------------------------------------------------------------
Car
|
Packets:
0
|
Bytes:
0
---------------------------------------------------------------------
Board : 2/1
---------------------------------------------------------------------
Matched
| Packets: 183
|
Bytes:
27,816
|
Rate(pps):
0
|
Rate(bps):
736
---------------------------------------------------------------------
Passed
|
Packets:
183
|
Bytes:
27,816
|
Rate(pps):
0
|
Rate(bps): 736
---------------------------------------------------------------------
Dropped
|
Packets:
0
|
Bytes:
0
| Rate(pps): 0
|
Rate(bps):
0
---------------------------------------------------------------------
Filter
|
Packets:
0
|
Bytes: 0
---------------------------------------------------------------------
Car
|
Packets:
0
|
Bytes:
0
---------------------------------------------------------------------
Step 2 Run the display cpu-defend statistics all command. It is found that a large number of ARP Miss packets are lost in slot 1/1.
<S7706> display cpu-defend
statistics all
Statistics on slot 1/1:
--------------------------------------------------------------------------------
Packet Type
Pass(Packet/Byte) Drop(Packet/Byte)
Last-dropping-time
--------------------------------------------------------------------------------
arp-miss
230819 267430
2017-09-01 20:00
30890324 40648513
Step 3 Capture packets in the outbound direction of the WOL server.
...
Based on analysis of the captured packets, the WOL server takes 3 to 4 seconds to send packets for a batch wake-up. A total of 3040 UDP packets are sent, so the WOL server sends about 1000 UDP packets every second. However, the default CPCAR value for ARP Miss packets is 64 kbit/s on the S7706. When the default configuration is used and the WOL server sends a large number of UDP packets within a short period, the S7706 drops packets due to the rate limit.
Step 4 Increase the default CPCAR value for ARP Miss packets on the MPU and LPU.
In attack defense policy 1, increase the rate limit of sending ARP Miss packets to the CPU to 2048 kbit/s.
[S7706] cpu-defend policy 1
[S7706-cpu-defend-policy-1] car packet-type arp-miss cir 2048
Apply attack defense policy 1 to slot 1/1.
[S7706] slot 1/1
[S7706-slot-1/1] cpu-defend-policy 1
Apply attack defense policy 1 to slot 2/1.
[S7706] slot 2/1
[S7706-slot-2/1] cpu-defend-policy 1
Apply attack defense policy 1 to the MPU.
[S7706] cpu-defend policy 1
----End
