The MTU value causes the kvm vm wget and SCP to fail.

Symptom: failed machine wget cannot be downloaded, and the test machine cannot issue the SCP file to the faulty machine, but the faulty machine can issue the SCP file to the test machine.

Tcpdump packet capture on the faulty machine finds that the data packet transmission between the faulty machine and the test machine is very slow, and the MTU problem of the faulty machine is suspected.

Normal is 1200, faulty machine is 1500

1. View MTU Value

# Cat/sys/class/NET/eth0/MTU

2. Modify MTU Value

# Echo "1200">/sys/class/NET/eth0/MTU

Or

Modify/etc/sysconfig/network-script/ifcfg-eth0

MTU = "1200"

Normal after modification to 1200

MTU is called maximum transmission unit, which indicates the maximum transmission unit, that is, the maximum number of bytes of the transmitted information package during connection. MTU determines the size of the information package. If the information package is too small, data of the same size will be divided into multiple packages for transmission, and the computer has to respond frequently; if the information package is too large, an error occurs, resulting in transmission failure.

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The MTU value causes the kvm vm wget and SCP to fail.