[All About Switches] Some Samsung Boxes Connected to a Switch Fail to Be Awakened Through WOL

Created: Mar 9, 2018 09:46:34Latest reply: Mar 12, 2018 10:14:01 1128 2 0 0

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

20180309094622979001.png

 

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.

20180309094623713002.jpg

...

20180309094623952003.jpg

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

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WoodWood     Created Mar 9, 2018 13:54:20 Helpful(0) Helpful(0)

:)
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ahricomambo4u  Visitor   Created Mar 12, 2018 10:14:01 Helpful(0) Helpful(0)

:)
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