[ofa-general] MTU in IPoIB

[Robert Dunkley]

Hi,

This warning is normal. If you don't need Multicast then it is of no
concern at all. If you have an app that uses multicast then you will
have to limit the MTU (In this case you might be better off using
reliable transmission - not connected mode).

Rob

-----Original Message-----
From: general-bounces at lists.openfabrics.org
[mailto:general-bounces at lists.openfabrics.org] On Behalf Of Wiegers,
Bert
Sent: 18 May 2009 12:11
To: general at lists.openfabrics.org
Subject: [ofa-general] MTU in IPoIB

Hi,

In our default-setup we are using IPoIB. This is set up with a MTU of
65520

ib0       Link encap:UNSPEC  HWaddr
80-00-00-48-FE-80-00-00-00-00-00-00-00-00-00-00
          inet addr:10.75.107.32  Bcast:10.75.255.255  Mask:255.255.0.0
          inet6 addr: fe80::214:4fa4:d3ba:25/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:65520  Metric:1
          RX packets:9318 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4197 errors:0 dropped:10 overruns:0 carrier:0
          collisions:0 txqueuelen:4096
          RX bytes:25032362 (23.8 Mb)  TX bytes:636320 (621.4 Kb)



Our dmesg on the other hand shows these hints:


ib_core: module not supported by Novell, setting U taint flag.
ib_mad: module not supported by Novell, setting U taint flag.
ib_mthca: module not supported by Novell, setting U taint flag.
mlx4_ib: module not supported by Novell, setting U taint flag.
mlx4_ib: Mellanox ConnectX InfiniBand driver v1.0 (April 4, 2008)
ib_ipath: module not supported by Novell, setting U taint flag.
cxgb3: module not supported by Novell, setting U taint flag.
iw_cxgb3: module not supported by Novell, setting U taint flag.
ib_umad: module not supported by Novell, setting U taint flag.
NET: Registered protocol family 10
lo: Disabled Privacy Extensions
IPv6 over IPv4 tunneling driver
ib_uverbs: module not supported by Novell, setting U taint flag.
ib_sa: module not supported by Novell, setting U taint flag.
ib_cm: module not supported by Novell, setting U taint flag.
ib_ipoib: module not supported by Novell, setting U taint flag.
ADDRCONF(NETDEV_UP): ib0: link is not ready
ib0: enabling connected mode will cause multicast packet drops
ib0: mtu > 2044 will cause multicast packet drops.
ib0: mtu > 2044 will cause multicast packet drops.
ib1: enabling connected mode will cause multicast packet drops
ib1: mtu > 2044 will cause multicast packet drops.
ib1: mtu > 2044 will cause multicast packet drops.
ib_addr: module not supported by Novell, setting U taint flag.
iw_cm: module not supported by Novell, setting U taint flag.
rdma_cm: module not supported by Novell, setting U taint flag.
ib_sdp: module not supported by Novell, setting U taint flag.
NET: Registered protocol family 27
qlgc_vnic: module not supported by Novell, setting U taint flag.
QLGC_VNIC: Initializing QLogic Corp. Virtual NIC (VNIC) driver version
1.3.0.0.4
rdma_ucm: module not supported by Novell, setting U taint flag.
scsi_transport_iscsi: module not supported by Novell, setting U taint
flag.
Loading iSCSI transport class v2.0-869.
libiscsi: module not supported by Novell, setting U taint flag.
iscsi_tcp: module not supported by Novell, setting U taint flag.
iscsi: registered transport (tcp)
ib_iser: module not supported by Novell, setting U taint flag.
iscsi: registered transport (iser)
md: Autodetecting RAID arrays.
md: autorun ...
md: ... autorun DONE.
ib0: multicast join failed for ff12:401b:ffff:0000:0000:0000:ffff:ffff,
status -11
ADDRCONF(NETDEV_CHANGE): ib0: link becomes ready
eth0: no IPv6 routers present
ib0: no IPv6 routers present



So should I limit the MTU to 2044?

Thanks.

Bert
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