[CentOS] Cannot set MTU != 1500 on Intel NIC

Fri Aug 20 07:36:03 UTC 2010
Timo Schoeler <timo.schoeler at riscworks.net>

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thus Timo Schoeler spake:
> Hi list,

Little followup,

> I have a *very* strange problem, unfortunately it's kind of a show
> stopper regarding the deployment of the machine. :(
> 
> I have two Intel Gigabit Ethernet NICs on board (Supermicro-based
> Server), quoting lspci (full output see at the end of the email):
> 
> 0d:00.0 Ethernet controller: Intel Corporation 82573E Gigabit Ethernet
> Controller (Copper) (rev 03)
> 0f:00.0 Ethernet controller: Intel Corporation 82573L Gigabit Ethernet
> Controller

I tried with Intel's most recent driver, it shows the same behaviour:

[root at bla ~]# ip link set dev eth0 mtu 1576
SIOCSIFMTU: Invalid argument
[root at bla ~]# ip link set dev eth1 mtu 1576
[root at bla ~]# ip link show dev eth1
6: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1576 qdisc pfifo_fast
qlen 1000
    link/ether 00:30:48:xx:xx:xy brd ff:ff:ff:ff:ff:ff

Timo

> While the first device (seen as eth0) does *not* allow to set a
> different MTU (tried with 1576 and 1546, both values I could use; I am
> forced to use values >1500 here due to protocol stuff), the second works
> without a problem.
> 
> dmesg shows:
> 
> eth0: Unsupported MTU setting
> ADDRCONF(NETDEV_UP): eth0: link is not ready
> eth1: changing MTU from 1500 to 1576
> ADDRCONF(NETDEV_UP): eth1: link is not ready
> 802.1Q VLAN Support v1.8 Ben Greear <greearb at candelatech.com>
> All bugs added by David S. Miller <davem at redhat.com>
> ADDRCONF(NETDEV_UP): eth0.543: link is not ready
> ADDRCONF(NETDEV_UP): eth0.820: link is not ready
> e1000e: eth0 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: None
> ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
> ADDRCONF(NETDEV_CHANGE): eth0.543: link becomes ready
> ADDRCONF(NETDEV_CHANGE): eth0.820: link becomes ready
> e1000e: eth1 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: None
> ADDRCONF(NETDEV_CHANGE): eth1: link becomes ready
> 
> The MTU is set as usual in the ifcfg-ethN files as 'MTU=1576', e.g.
> 
> I tried with kernel 2.6.18-194.8.1.el5.028stab070.2 (OpenVZ) as well as
> the vanilla CentOS kernels 2.6.18-194.8.1.el5 and 2.6.18-194.11.1.el5 --
> same problem.
> 
> Has anybody an idea what goes wrong here?
> 
> Thanks,
> 
> Timo
> 
> ---
> 
> 0d:00.0 Ethernet controller: Intel Corporation 82573E Gigabit Ethernet
> Controller (Copper) (rev 03)
>         Subsystem: Super Micro Computer Inc Unknown device 108c
>         Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop-
> ParErr+ Stepping- SERR+ FastB2B-
>         Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort-
> <TAbort- <MAbort- >SERR- <PERR-
>         Latency: 0, Cache Line Size: 64 bytes
>         Interrupt: pin A routed to IRQ 90
>         Region 0: Memory at d0200000 (32-bit, non-prefetchable) [size=128K]
>         Region 2: I/O ports at 2000 [size=32]
>         Capabilities: [c8] Power Management version 2
>                 Flags: PMEClk- DSI+ D1- D2- AuxCurrent=0mA
> PME(D0+,D1-,D2-,D3hot+,D3cold+)
>                 Status: D0 PME-Enable- DSel=0 DScale=1 PME-
>         Capabilities: [d0] Message Signalled Interrupts: 64bit+
> Queue=0/0 Enable+
>                 Address: 00000000fee01000  Data: 405a
>         Capabilities: [e0] Express Endpoint IRQ 0
>                 Device: Supported: MaxPayload 256 bytes, PhantFunc 0,
> ExtTag-
>                 Device: Latency L0s <512ns, L1 <64us
>                 Device: AtnBtn- AtnInd- PwrInd-
>                 Device: Errors: Correctable+ Non-Fatal+ Fatal+ Unsupported+
>                 Device: RlxdOrd+ ExtTag- PhantFunc- AuxPwr- NoSnoop+
>                 Device: MaxPayload 128 bytes, MaxReadReq 512 bytes
>                 Link: Supported Speed 2.5Gb/s, Width x1, ASPM unknown,
> Port 0
>                 Link: Latency L0s <128ns, L1 <64us
>                 Link: ASPM Disabled RCB 64 bytes CommClk+ ExtSynch-
>                 Link: Speed 2.5Gb/s, Width x1
>         Capabilities: [100] Advanced Error Reporting
>         Capabilities: [140] Device Serial Number xy-xx-xx-ff-ff-48-30-00
> 
> 0f:00.0 Ethernet controller: Intel Corporation 82573L Gigabit Ethernet
> Controller
>         Subsystem: Super Micro Computer Inc Unknown device 109a
>         Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop-
> ParErr+ Stepping- SERR+ FastB2B-
>         Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort-
> <TAbort- <MAbort- >SERR- <PERR-
>         Latency: 0, Cache Line Size: 64 bytes
>         Interrupt: pin A routed to IRQ 106
>         Region 0: Memory at d0300000 (32-bit, non-prefetchable) [size=128K]
>         Region 2: I/O ports at 3000 [size=32]
>         Capabilities: [c8] Power Management version 2
>                 Flags: PMEClk- DSI+ D1- D2- AuxCurrent=0mA
> PME(D0+,D1-,D2-,D3hot+,D3cold+)
>                 Status: D0 PME-Enable- DSel=0 DScale=1 PME-
>         Capabilities: [d0] Message Signalled Interrupts: 64bit+
> Queue=0/0 Enable+
>                 Address: 00000000fee01000  Data: 406a
>         Capabilities: [e0] Express Endpoint IRQ 0
>                 Device: Supported: MaxPayload 256 bytes, PhantFunc 0,
> ExtTag-
>                 Device: Latency L0s <512ns, L1 <64us
>                 Device: AtnBtn- AtnInd- PwrInd-
>                 Device: Errors: Correctable+ Non-Fatal+ Fatal+ Unsupported+
>                 Device: RlxdOrd+ ExtTag- PhantFunc- AuxPwr- NoSnoop+
>                 Device: MaxPayload 128 bytes, MaxReadReq 512 bytes
>                 Link: Supported Speed 2.5Gb/s, Width x1, ASPM unknown,
> Port 0
>                 Link: Latency L0s <128ns, L1 <64us
>                 Link: ASPM Disabled RCB 64 bytes CommClk+ ExtSynch-
>                 Link: Speed 2.5Gb/s, Width x1
>         Capabilities: [100] Advanced Error Reporting
>         Capabilities: [140] Device Serial Number xx-xx-xx-ff-ff-48-30-00
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