PowerFlex 3.0: Gateway Analyze System reports "MTU on route is not uniform"

One or more VxFlex OS components are hosted on Red Hat or derivative Linux distributions, including CentOS-based SVM.

In the report generated by the Analyze System Gateway feature, under the Network section, in the table shown under Connectivity, one or more "MTU on route to component (IP: Address) is not uniform" issues appears.

Impact

System diagnosis fails to correctly identify whether or not an issue exists.

Manually verify that the MTU is set correctly along all control and data paths, by transmitting packets of the maximum size allowed by the MTU configured for the NICs.

On the Primary MDM note down all IP addresses configured for use with components' control and data transmission.

scli --query_cluster |grep 'IPs' |sed 's/, [^0-9].*//;s/.*IPs: //' 
scli --query_all_sds |grep '^SDS' |sed 's/.*IP: //;s/ [^0-9].*//' 
scli --query_all_sdc |grep '^SDC' |sed 's/.*IP: //;s/ [^0-9].*//'

From each Linux host (including SVM) to a VxFlex OS backend (MDM and SDS) component, verify that packets of the maximum allowed size can be transmitted to each of the IP addresses noted down in the previous step.

addr='' interface="$(ip route get "${addr}" |grep dev |sed 's/.* dev *//;s/ .*//')" mtu="$(ip addr list "${interface}" |grep mtu |sed 's/.* mtu *//;s/ .*//')" ping -W 2 -c 3 -i 0.2 -M do -s "$((mtu - 28))" "${addr}"

Example and corresponding output:

# addr='123.234.234.7' # interface="$(ip route get "${addr}" |grep dev |sed 's/.* dev *//;s/ .*//')" # mtu="$(ip addr list "${interface}" |grep mtu |sed 's/.* mtu *//;s/ .*//')" # ping -W 2 -c 3 -i 0.2 -M do -s "$((mtu - 28))" "${addr}" PING 123.234.234.7 (123.234.234.7) 8972(9000) bytes of data. 8980 bytes from 123.234.234.7: icmp_seq=1 ttl=64 time=0.166 ms 8980 bytes from 123.234.234.7: icmp_seq=2 ttl=64 time=0.143 ms 8980 bytes from 123.234.234.7: icmp_seq=3 ttl=64 time=0.150 ms --- 123.234.234.7 ping statistics --- 3 packets transmitted, 3 received, 0% packet loss, time 400ms rtt min/avg/max/mdev = 0.143/0.153/0.166/0.009 ms

In the output of ping with the maximum allowed packet size, note 0% packet loss.

Impacted Versions

PowerFlex 3.0.x