[CentOS] MTU report question

Tue Dec 15 07:48:53 UTC 2020
Patrick Bégou <Patrick.Begou at legi.grenoble-inp.fr>

Hi Strahil

I get:

ping: local error: Message too long, mtu=2044
ping: local error: Message too long, mtu=2044

so ip report is correct and nmcli did not the job ?

Patrick

Le 14/12/2020 à 20:23, Strahil Nikolov via CentOS a écrit :
> 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: 
>
>
>
>
>
> Hi,
>
> 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....)?
>
> Thanks
>
> Patrick
>
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