Como posso obter a NIC para responder aos pacotes jumbo quando a MTU estiver configurada para 4000?

Question

Eu tenho um servidor do mythbuntu 14.04.

# uname -a
Linux KISE-055 3.16.0-55-generic #74~14.04.1-Ubuntu SMP Tue Nov 17 10:15:59 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

Eu tenho o MTU configurado para 4000 vice 1500 para obter pacotes jumbo ...

# ip link
...
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 4000 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000
link/ether 90:fb:a6:eb:d7:f3 brd ff:ff:ff:ff:ff:ff

Eu configurei o MTU em /etc/network/interfaces

# cat /etc/network/interfaces
auto lo
iface lo inet loopback
#primary wired interface
auto eth0
iface eth0 inet dhcp
post-up /sbin/ifconfig eth0 mtu 4000

Que pode ser visto na saída de 'ifconfig' ...

~$ ifconfig
eth0      Link encap:Ethernet  HWaddr 90:fb:a6:eb:d7:f3
      inet addr:192.168.0.55  Bcast:192.168.0.255  Mask:255.255.255.0
      inet6 addr: fe80::92fb:a6ff:feeb:d7f3/64 Scope:Link
  ⇛ ⇛ UP BROADCAST RUNNING MULTICAST  MTU:4000  Metric:1  ⇚ ⇚
      RX packets:43654 errors:0 dropped:0 overruns:0 frame:0
      TX packets:41807 errors:0 dropped:0 overruns:0 carrier:0
      collisions:0 txqueuelen:1000
      RX bytes:29877609 (29.8 MB)  TX bytes:21276131 (21.2 MB)

lo        Link encap:Local Loopback
      inet addr:127.0.0.1  Mask:255.0.0.0
      inet6 addr: ::1/128 Scope:Host
      UP LOOPBACK RUNNING  MTU:65536  Metric:1
      RX packets:2010 errors:0 dropped:0 overruns:0 frame:0
      TX packets:2010 errors:0 dropped:0 overruns:0 carrier:0
      collisions:0 txqueuelen:0
      RX bytes:279223 (279.2 KB)  TX bytes:279223 (279.2 KB)

Mas o sistema não responde aos pacotes jumbo de outros computadores na LAN. Portanto, todos os clientes devem usar um MTU de 1500 para falar com o servidor.

Aqui está o nic ...

02:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 03)
    Subsystem: Foxconn International, Inc. Device 0e22
    Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx+
    Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
    Latency: 0, Cache Line Size: 64 bytes
    Interrupt: pin A routed to IRQ 47
    Region 0: I/O ports at e800 [size=256]
    Region 2: Memory at fafff000 (64-bit, prefetchable) [size=4K]
    Region 4: Memory at faff8000 (64-bit, prefetchable) [size=16K]
    Expansion ROM at fdfe0000 [disabled] [size=128K]
    Capabilities: [40] Power Management version 3
            Flags: PMEClk- DSI- D1+ D2+ AuxCurrent=375mA PME(D0+,D1+,D2+,D3hot+,D3cold+)
            Status: D0 NoSoftRst+ PME-Enable- DSel=0 DScale=0 PME-
    Capabilities: [50] MSI: Enable+ Count=1/1 Maskable- 64bit+
            Address: 00000000fee0200c  Data: 4142
    Capabilities: [70] Express (v2) Endpoint, MSI 01
            DevCap: MaxPayload 256 bytes, PhantFunc 0, Latency L0s <512ns, L1 <64us
                    ExtTag- AttnBtn- AttnInd- PwrInd- RBE+ FLReset-
            DevCtl: Report errors: Correctable- Non-Fatal- Fatal- Unsupported-
                    RlxdOrd- ExtTag- PhantFunc- AuxPwr- NoSnoop-
                    MaxPayload 128 bytes, MaxReadReq 512 bytes
            DevSta: CorrErr+ UncorrErr- FatalErr- UnsuppReq+ AuxPwr+ TransPend-
            LnkCap: Port #0, Speed 2.5GT/s, Width x1, ASPM L0s L1, Exit Latency L0s <512ns, L1 <64us
                    ClockPM+ Surprise- LLActRep- BwNot-
            LnkCtl: ASPM Disabled; RCB 64 bytes Disabled- CommClk+
                    ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-
            LnkSta: Speed 2.5GT/s, Width x1, TrErr- Train- SlotClk+ DLActive- BWMgmt- ABWMgmt-
            DevCap2: Completion Timeout: Not Supported, TimeoutDis+, LTR-, OBFF Not Supported
            DevCtl2: Completion Timeout: 50us to 50ms, TimeoutDis-, LTR-, OBFF Disabled
            LnkCtl2: Target Link Speed: 2.5GT/s, EnterCompliance- SpeedDis-
                     Transmit Margin: Normal Operating Range, EnterModifiedCompliance- ComplianceSOS-
                     Compliance De-emphasis: -6dB
            LnkSta2: Current De-emphasis Level: -6dB, EqualizationComplete-, EqualizationPhase1-
                     EqualizationPhase2-, EqualizationPhase3-, LinkEqualizationRequest-
    Capabilities: [ac] MSI-X: Enable- Count=4 Masked-
            Vector table: BAR=4 offset=00000000
            PBA: BAR=4 offset=00000800
    Capabilities: [cc] Vital Product Data
            Unknown small resource type 00, will not decode more.
    Capabilities: [100 v1] Advanced Error Reporting
            UESta:  DLP- SDES- TLP- FCP- CmpltTO- CmpltAbrt- UnxCmplt- RxOF- MalfTLP- ECRC- UnsupReq- ACSViol-
            UEMsk:  DLP- SDES- TLP- FCP- CmpltTO- CmpltAbrt- UnxCmplt- RxOF- MalfTLP- ECRC- UnsupReq- ACSViol-
            UESvrt: DLP+ SDES+ TLP- FCP+ CmpltTO- CmpltAbrt- UnxCmplt- RxOF+ MalfTLP+ ECRC- UnsupReq- ACSViol-
            CESta:  RxErr- BadTLP- BadDLLP- Rollover- Timeout- NonFatalErr+
            CEMsk:  RxErr- BadTLP- BadDLLP- Rollover- Timeout- NonFatalErr+
            AERCap: First Error Pointer: 00, GenCap+ CGenEn- ChkCap+ ChkEn-
    Capabilities: [140 v1] Virtual Channel
            Caps:   LPEVC=0 RefClk=100ns PATEntryBits=1
            Arb:    Fixed- WRR32- WRR64- WRR128-
            Ctrl:   ArbSelect=Fixed
            Status: InProgress-
            VC0:    Caps:   PATOffset=00 MaxTimeSlots=1 RejSnoopTrans-
                    Arb:    Fixed- WRR32- WRR64- WRR128- TWRR128- WRR256-
                    Ctrl:   Enable+ ID=0 ArbSelect=Fixed TC/VC=ff
                    Status: NegoPending- InProgress-
    Capabilities: [160 v1] Device Serial Number 16-00-00-00-68-4c-e0-00
    Kernel driver in use: r8169

    

Answer 1

Eu tenho uma pergunta sobre seu ambiente, que tipo de switch você tem? e é o switch configurado para Jumbo Frames.