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[Troubleshooting Series] Case 53 Two Direct Connected Devices Ping Time Delay

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Hello everyone,

I will share with you how to deal with two direct connected devices ping time delay.

Physical Network Topology

Figure 1-1 Two direct connected devices ping time delay

152621bwjcsjr87scmcv8b.png

Fault Description

When SwitchA pings SwitchB, the ICMP delay is very large. The specific 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=255 time=52 ms

    Reply from 111.111.1.3: bytes=56 Sequence=2 ttl=255 time=52 ms

    Reply from 111.111.1.3: bytes=56 Sequence=3 ttl=255 time=51 ms

    Reply from 111.111.1.3: bytes=56 Sequence=4 ttl=255 time=51 ms

    Reply from 111.111.1.3: bytes=56 Sequence=5 ttl=255 time=51 ms

When pinging with the -r parameter, the delay is very small, as follows:

[CE12800_A]ping -r 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=22 ms

    Record Route:

      111.111.1.3

      111.111.1.1

    Reply from 111.111.1.3: bytes=56 Sequence=2 ttl=255 time=2 ms

    Record Route:

      111.111.1.3

      111.111.1.1

    Reply from 111.111.1.3: bytes=56 Sequence=3 ttl=255 time=2 ms

    Record Route:

      111.111.1.3

      111.111.1.1

    Reply from 111.111.1.3: bytes=56 Sequence=4 ttl=255 time=2 ms

    Record Route:

      111.111.1.3

      111.111.1.1

    Reply from 111.111.1.3: bytes=56 Sequence=5 ttl=255 time=2 ms

    Record Route:

      111.111.1.3

Configuration Files

Configuration 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

#

Configuration on SwitchB

#

interface 10GE2/0/1

 port link-type trunk

 port trunk allow-pass vlan 10 to 30 1000 1111

 stp disable

 device transceiver 10GBASE-COPPER

#

interface Vlanif1111

 ip address 111.111.1.3 255.255.255.0

icmp name host-unreachable receive disable

 icmp name redirect receive disable

#

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. The details are as follows.

<CE12800_B>debugging ip icmp 

Oct 21 2018 21:46:48.225 switch-C %PP4/7/icmp_packet(d):CID=0x8066274d;ICMP Receive: echo(Type=8, Code=0, Chksum=0xd3fe),IfIndex = 253, Vrf = 0, EventId = 0, Flag = 0x200, Src = 111.111.1.1, Dst = 111.111.1.3,ICMP Id = 0x2400, ICMP Seq = 0x1

Oct 21 2018 21:46:48.233 switch-C %PP4/7/icmp_packet(d):CID=0x8066274d;ICMP Send: echo-reply(Type=0, Code=0, Chksum=0xdbfe),IfIndex = 253, Vrf = 0, EventId = 0, Flag = 0x100200, Src = 111.111.1.3, Dst = 111.111.1.1,ICMP Id = 0x2400, ICMP Seq = 0x1

After ICMP debugging is enabled, it is found that no ICMP is sent to the CPU.

Step 3 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:                           5                            

     destination is not host ip:                  0                            

     failed to get ctrl word:                     0                            

Send packets:                                                                  

     successful reply packets:                    5                            

     failed reply packets:                        0      

When the packet is ICMP fast return, the interface board processes the packets at the same time, and these data interface boards do not need to be processed.

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

The problem has been solved.

Root Cause

After the ICMP unreachable packet is not received funcion is enabled on the device, the packet is first processed by ICMP. After the packet is processed, the packet is sent to the CPU for processing. This causes excessive performance.

This is what I want to share with you, thank you!

 


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