IRQ mismatch ifconfig and /proc/interrupts

[Oscar Salvador]

Hi People! How are you doing?

I'm writting to you because I have a doubt about interrupts.

If I look the interrupts assigned to my eth* with ifconfig, I get:

eth0      Link encap:Ethernet  HWaddr bb:aa:bb:bb:aa:aa  
          Interrupt:20 Memory:f7e00000-f7e20000 

eth1      Link encap:Ethernet  HWaddr bb:aa:bb:bb:aa:aa  
          Interrupt:18 Memory:f7d00000-f7d20000

As you can see, my system assigned IRQ-20 and IRQ-18 to eth0 and eth1.

But If i look into /proc/interrupts, I don't have these interrupts:

root at oscar:/home/oscar# cat /proc/interrupts 
           CPU0       CPU1       CPU2       CPU3       CPU4       CPU5       CPU6       CPU7       
  0:         15          0          0          0          0          0          0          0  IR-IO-APIC-edge      timer
  8:          0          1          0          0          0          0          0          0  IR-IO-APIC-edge      rtc0
  9:          0          0          0          0          0          2          1          0  IR-IO-APIC-fasteoi   acpi
 16:     191342      27819      25143      21231      19007      18159      17183      15717  IR-IO-APIC-fasteoi   ehci_hcd:usb3
 19:         15          7          0          0          2          9          1          4  IR-IO-APIC-fasteoi   firewire_ohci
 23:       1441         76         61         42        101         55         29         23  IR-IO-APIC-fasteoi   ehci_hcd:usb4
 40:          0          0          0          0          0          0          0          0  DMAR_MSI-edge      dmar0
 41:          0          0          0          0          0          0          0          0  DMAR_MSI-edge      dmar1
 42:          0          0          0          0          0          0          0          0  IR-PCI-MSI-edge      xhci_hcd
 43:      27318       1788       1314       1414       4046       2273       2232       2059  IR-PCI-MSI-edge      eth0
 44:     115244      14686      10096       8738      41559      16021      10972      10090  IR-PCI-MSI-edge      ahci
 45:     197010      19487      45260      14687      43697      29520      24546      21590  IR-PCI-MSI-edge      eth1-rx-0
 46:      27239      20276      18861      14845      54218      17950      12907       9765  IR-PCI-MSI-edge      eth1-tx-0
 47:          0          0          1          0          0          0          0          1  IR-PCI-MSI-edge      eth1
 48:        262        150         78         60        261        249        168         47  IR-PCI-MSI-edge      snd_hda_intel
 49:     857324      80338      67789      59555     682632      90385      78616      65048  IR-PCI-MSI-edge      i915


As you can see, seems to be that eth1 has IRQ-45 IRQ-46 and IRQ-47, and eth0 has IRQ-43.
I don't understand why ifconfig shows another IRQ. 

Is this a normal behaviour? Someone would be so kind to explain me this?

Or maybe throw me some paper that explains this.

thank you very much
Best Regards

Oscar