Involved Products and Versions
All products and versions
Networking
As shown in Figure 1-1, the gateway SwitchA is connected to the Layer 2 device SwitchB, which is then connected to a PC.
Figure 1-1 Networking diagram for the communication failure between a PC and the gateway due to the rate limit of ARP Miss packets
Fault Symptom
The PC and SwitchA cannot communicate with each other.
Cause Analysis
The rate limit of ARP Miss packets is incorrectly configured.
Troubleshooting Procedure
Step 1 Run the display cpu-defend statistics allcommand. It is found that a large number of ARP Miss packets and ARP Request packets are sent to the CPU for processing while a large number of these packets are discarded.
<SwitchA> display cpu-defend
statistics all
Statistics on slot 1:
--------------------------------------------------------------------------------
Packet Type Pass(Packet/Byte) Drop(Packet/Byte) Last-dropping-time
--------------------------------------------------------------------------------
arp-miss
135576021
1601690 2017-03-31 05:17
14520988007 513234651
arp-reply
281572
0 -
18113898
0
arp-request
39556247 2009617
2017-03-31 05:17
2536513490 128877696
fib-hit
229127
13806 2017-03-31 05:17
41911145 1577046
Step 2 Check the configuration on SwitchA. It is found that the rate limit of ARP Miss packets is configured.
arp-miss anti-attack rate-limit
enable
arp-miss anti-attack rate-limit packet 16384 interval 84600
arp-miss speed-limit source-ip maximum 16384
According to the preceding configuration, the arp-miss anti-attack rate-limit packet 16384 interval 84600 command is improper. On average, only 0.1 ARP Miss packets can be processed per second. However, there are many ARP Miss packets on the live network. After the arp-miss anti-attack rate-limit packet 16384 interval 84600 and arp-miss speed-limit source-ip maximum 16384 commands are deleted, the fault is rectified.
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