If a device is placed on a VLAN and attempts network boot (PXE) without any TFTP server configured, a substantial (~15%) packet loss occurs between other clients on the same VLAN and VyOS router (ethernet vif interface) for the duration when the device is attempting to perform network boot - might be indefinitely for e.g. thin clients.
$ monitor traffic interface eth1.30 | match boot* tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on eth1.30, link-type EN10MB (Ethernet), capture size 262144 bytes 10:52:45.044826 IP 71b3c109d87b.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from 00:23:24:67:b7:19 (oui Unknown), length 548 10:52:46.046335 IP 10.3.0.1.bootps > 255.255.255.255.bootpc: BOOTP/DHCP, Reply, length 300 10:52:46.046926 IP 10.3.0.1.bootps > 255.255.255.255.bootpc: BOOTP/DHCP, Reply, length 300 10:52:49.053862 IP 71b3c109d87b.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from 00:23:24:67:b7:19 (oui Unknown), length 548 10:52:50.055556 IP 10.3.0.1.bootps > 255.255.255.255.bootpc: BOOTP/DHCP, Reply, length 300 10:52:50.055823 IP 10.3.0.1.bootps > 255.255.255.255.bootpc: BOOTP/DHCP, Reply, length 300
No TFTP is configured on this VyOS instance nor is DHCP server pointing to another TFTP server:
$ show service dhcp-server shared-network-name VLAN30 authoritative subnet 10.3.0.0/24 { default-router 10.3.0.1 dns-server 10.3.0.1 range 0 { start 10.3.0.100 stop 10.3.0.199 } }