[CentOS] MTU report question

Mon Dec 14 19:23:36 UTC 2020
Strahil Nikolov <hunter86_bg at yahoo.com>

what happens when you 'ping -M do -s 65000 -c 4 <other IBoIP system> ?

Best Regards,
Strahil Nikolov

В понеделник, 14 декември 2020 г., 15:46:50 Гринуич+2, Patrick Bégou <patrick.begou at legi.grenoble-inp.fr> написа: 


I'm deploying a CentOS8 (not stream 😁) cluster and I have a question
about MTU on the interfaces. I have a connectX6 Mellanox interface where
I need IBoIP setup.
I've setup this interface via nmcli and set the MTU to 65520 with:

    nmcli connection modify ib0 mtu 65520
    nmcli connection up ib0

Running "nmcli connection show ib0" report:

    infiniband.mtu:                         65520

But "ip addr show ib0" report a mtu of 2044:

    6: ib0: <BROADCAST,MULTICAST,UP,LOWER_UP> *mtu 2044 *qdisc mq state
    UP group default qlen 256

Why ? Who is wrong (possibly me....)?



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