-nic user cannot receive TFTP response from outside on windows 10 host Configuration: qemu is on a windows 10 host, address 192.168.1.24 A tftp server, which is atftpd, is at address 192.168.1.31 a guest is started by: ``` .\qemu-system-x86_64.exe -accel hax \ -nic user,id=n1,tftp-server-name=192.168.1.31,bootfile=tftp://192.168.1.31/grub/i386-pc/core.0 \ -object filter-dump,id=f1,netdev=n1,file=dump.dat ``` qemu v4.2.0-11797-g2890edc853-dirty, from https://qemu.weilnetz.de/w64/ windows 10 1909 18363.628 Here is the captured traffic from dump.dat, no filter applied: No. Time Source Destination Protocol Length Info 1 0.000000 0.0.0.0 255.255.255.255 DHCP 439 DHCP Discover - Transaction ID 0xdb38340e 2 0.000081 10.0.2.2 255.255.255.255 DHCP 590 DHCP Offer - Transaction ID 0xdb38340e 3 1.035670 0.0.0.0 255.255.255.255 DHCP 439 DHCP Discover - Transaction ID 0xdb38340e 4 1.035693 10.0.2.2 255.255.255.255 DHCP 590 DHCP Offer - Transaction ID 0xdb38340e 5 3.068055 0.0.0.0 255.255.255.255 DHCP 451 DHCP Request - Transaction ID 0xdb38340e 6 3.068099 10.0.2.2 255.255.255.255 DHCP 590 DHCP ACK - Transaction ID 0xdb38340e 7 3.068209 RealtekU_12:34:56 Broadcast ARP 42 ARP Announcement for 10.0.2.15 8 3.148419 RealtekU_12:34:56 Broadcast ARP 42 Who has 10.0.2.2? Tell 10.0.2.15 9 3.148449 52:55:0a:00:02:02 RealtekU_12:34:56 ARP 64 10.0.2.2 is at 52:55:0a:00:02:02 10 3.148511 10.0.2.15 192.168.1.31 TFTP 91 Read Request, File: grub/i386-pc/core.0, Transfer type: octet, blksize=1432, tsize=0 11 3.398093 10.0.2.15 192.168.1.31 TFTP 91 Read Request, File: grub/i386-pc/core.0, Transfer type: octet, blksize=1432, tsize=0 12 3.946041 10.0.2.15 192.168.1.31 TFTP 91 Read Request, File: grub/i386-pc/core.0, Transfer type: octet, blksize=1432, tsize=0 13 4.990262 10.0.2.15 192.168.1.31 TFTP 91 Read Request, File: grub/i386-pc/core.0, Transfer type: octet, blksize=1432, tsize=0 14 7.022839 10.0.2.15 192.168.1.31 TFTP 91 Read Request, File: grub/i386-pc/core.0, Transfer type: octet, blksize=1432, tsize=0 15 11.087041 10.0.2.15 192.168.1.31 TFTP 91 Read Request, File: grub/i386-pc/core.0, Transfer type: octet, blksize=1432, tsize=0 Here is the captured traffic at host NIC, filered by from or to 192.168.1.31 No. Time Source Destination Protocol Length Info 14140 57.729066 192.168.1.24 192.168.1.31 TFTP 91 Read Request, File: grub/i386-pc/core.0, Transfer type: octet, blksize=1432, tsize=0 14141 57.732988 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 14255 57.977995 192.168.1.24 192.168.1.31 TFTP 91 Read Request, File: grub/i386-pc/core.0, Transfer type: octet, blksize=1432, tsize=0 14256 57.979876 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 14275 58.525939 192.168.1.24 192.168.1.31 TFTP 91 Read Request, File: grub/i386-pc/core.0, Transfer type: octet, blksize=1432, tsize=0 14276 58.527819 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 14328 59.570178 192.168.1.24 192.168.1.31 TFTP 91 Read Request, File: grub/i386-pc/core.0, Transfer type: octet, blksize=1432, tsize=0 14329 59.581024 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 14383 61.602742 192.168.1.24 192.168.1.31 TFTP 91 Read Request, File: grub/i386-pc/core.0, Transfer type: octet, blksize=1432, tsize=0 14384 61.605554 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 14730 62.736572 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 14741 62.987924 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 14756 63.533477 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 14815 64.577653 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 14916 65.666959 192.168.1.24 192.168.1.31 TFTP 91 Read Request, File: grub/i386-pc/core.0, Transfer type: octet, blksize=1432, tsize=0 14917 65.668778 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 15235 66.615186 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 15481 67.745250 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 15509 67.991523 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 15566 68.539050 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 16691 69.583531 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 17457 70.675366 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 17599 71.615337 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 17904 72.747338 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 18012 72.995681 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 18192 73.544257 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 18360 74.588002 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 18981 75.679037 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 19270 76.620528 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 19839 77.752338 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 19852 78.001267 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 19917 78.548965 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 20066 79.593232 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 20140 80.684604 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 20220 81.625996 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 20537 82.824574 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 20551 83.033318 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 20607 83.555510 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 20734 84.598612 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 20816 85.691535 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 20898 86.631036 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 22311 90.695296 192.168.1.31 192.168.1.24 TFTP 69 Option Acknowledgement, tsize=45542, blksize=1432 From the traffic, the guest sent the request properly, and it is rerouted outside properly, and the server respond to it properly. However, the guest never received the response.