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

Fri Aug 20 07:15:28 UTC 2010
Timo Schoeler <timo.schoeler at riscworks.net>

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Hi list,

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

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

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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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