[Troubleshooting Series] Case 52 ICMP Rate Limit does not Take Effect

Created: Feb 11, 2019 09:57:22 308 0 0 0


Physical Network Topology

As shown in the figure, two CE12800s are directly connected, and ICMP speed limit is configured on SwitchB. The command is as follows: icmp rate-limit interface 10GE 2/0/1 threshold 1

Figure 1-1 ICMP rate limit

091625u443k0l999tzan91.png

 

Fault Description

When SwitchA pings SwitchB, the ICMP speed limit function does not take effect on SwitchB. The detailed information is as follows:

[CE12800_A] ping 111.111.1.3
  PING 111.111.1.3: 56  data bytes, press CTRL_C to break
    Reply from 111.111.1.3: bytes=56 Sequence=1 ttl=254 time=1 ms
    Reply from 111.111.1.3: bytes=56 Sequence=2 ttl=254 time=1 ms
    Reply from 111.111.1.3: bytes=56 Sequence=3 ttl=254 time=1 ms
    Reply from 111.111.1.3: bytes=56 Sequence=4 ttl=254 time=1 ms
    Reply from 111.111.1.3: bytes=56 Sequence=5 ttl=254 time=1 ms
 
  --- 111.111.1.3 ping statistics ---
    5 packet(s) transmitted
    5 packet(s) received
    0.00% packet loss
    round-trip min/avg/max = 1/1/1 ms

Normally, there should be ICMP loss-limited packet loss.

Configuration Files

l   Confguration on SwitchA

#
interface Vlanif1111
 ip address 111.111.1.1 255.255.255.0
interface 10GE1/0/1
 port link-type trunk
 port trunk allow-pass vlan 5 10 to 30 300 1111 3000
 stp disable
 device transceiver 10GBASE-COPPER
#

l   Configuration on SwitchB

user-interface con 0
#
user-interface vty 0 4
 authentication-mode none
 user privilege level 3
 idle-timeout 0 0
 protocol inbound telnet
#
vm-manager
#
return

1.1.2 Troubleshooting Location

Troubleshooting Procedure

                               Step 1      Check that SwitchB receives the ICMP packet normally and finds that the packet has been sent from the chip to the CPU.

<CE12800_B> display cpu-defend statistics packet-type icmp slot 1/4  
Statistics(packets) on slot 1/4 :
--------------------------------------------------------------------------------
PacketType               Total Passed        Total Dropped   Last Dropping Time
                    Last 5 Min Passed   Last 5 Min Dropped
--------------------------------------------------------------------------------
icmp                                5                    0   -
                                    5                    0

                               Step 2      Check whether the CPU receives ICMP packets and speed limit on the CPU.

<CE12800_B> debugging ip icmp

                               Step 3      After ICMP debugging is enabled, it is found that no ICMP is sent to the CPU to check whether the interface board fast returns ICMP packets.

<CE12800_B> display icmp fast-reply statistics slot 1/4 
------------------------ Display ICMP Statistics -------------------------------
Received packets:                                                               
     request packets:                             5                             
     invalid request packets:                     0                             
     failed to get vrf:                           0                             
     destination is not host ip:                  0                             
     failed to get ctrl word:                     0                             
Send packets:                                                                    
     successful reply packets:                    5                             
     failed reply packets:                        0                             
--------------------------------------------------------------------------------

The display shows that ICMP packets are processed back by the interface and are not sent to the CPU of the main control board.

                               Step 4      Turn off the ICMP echo-reply fast function.

[CE12800_B] icmp echo-reply fast disable

                               Step 5      Verify on SwitchA as follows.

<CE12800_A> ping 111.111.1.3                                         
  PING 111.111.1.3: 56  data bytes, press CTRL_C to break
    Reply from 111.111.1.3: bytes=56 Sequence=1 ttl=255 time=15 ms
    Request time out
    Reply from 111.111.1.3: bytes=56 Sequence=3 ttl=255 time=2 ms
    Request time out
    Reply from 111.111.1.3: bytes=56 Sequence=5 ttl=255 time=1 ms
 
  --- 111.111.1.3 ping statistics ---
    5 packet(s) transmitted
    3 packet(s) received
    40.00% packet loss
round-trip min/avg/max = 1/6/15 ms

It has been verified that the ICMP speed limit function takes effect.

----End

Root Cause

The ICMP rate limit function is in conflict with the default ICMP rate limit function. The rate limit function does not take effect.

 


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