lol I thought it may have been as simple as that but best ask in case its some linux term I've never seen before!

So have thought about this but the debian vm is using systemd where this is using systemv so the ifconfig files are completely different.

Just compared the ip link output and they are indeed different:

Debian:
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN mode DEFAULT group default qlen 1000

Broken:
2: sit0@NONE: <NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1

The BROADCAST vs NOARP sticks out.

Doesn't the ARP Cache deal with ip to mac conversion for network devices to talk at hardware level?? layer 2 or 3 is it? can never remember they layer numbers from the top of my head!

loop back ping and its own ip ping absolutely fine.

nothing else is reachable.

no link-local address as not using dhcp, static set in ifconfig

no ip conflicts as the dhcp server scope doesn't cover the address I'm using.

ARP is used for mapping a network address (e.g. an IPv4 address) to a MAC address, and it's a process happens for every router until you reach destination, and vice versa. The hardware/IP addresses are stored in the ARP cache.. In IPv6 the functionality of ARP is provided by NDP (neighbor discovery protocol)..

so could the NOARP comment listed next to the sit0 adapter be related to this issue then?

A quick look at "man ip link" then search "NOARP" there are option(s) "arp on" and "arp off".. Maybe try the "arp on" option to turn your arp on.

so I've tried to set both arp and multicast on (just based on the debian compare) and hasn't made a difference.

I have noticed that the debian ip link output shows the mac address of the NIC where the broken build only shows

link/sit 0.0.0.0 brd 0.0.0.0

so tried to set the address using:

ip link set dev sit0 address 00:15:5d:69:5b:07

But it returns

Invalid address length 6 - must be 4 bytes

also tried setting it with LLADDR=00:15:5d:69:5b:07 and MACADDR=00:15:5d:69:5b:07 (wasn't sure what version applied to my ifconfig) variables in the ifconfig file but still nothing.

I going to compile the net-tools package so I can run arp to see what it has listed.

Thanks for the help! will post the results in a min.

To change the mac address first bring your interface down then type "ifconfig sit0 hw ether YourMacHere" then bring sit0 back up.

returns ifconfig: only one address allowed for interface 'sit0'

compiled net-tools and arp returns nothing with both the -a and -e swtiches

That's odd as that command is meant to spoof (or change) your mac address, not try and add new one.. Make sure you brought the interface down via "ifconfig sit0 down" then back up again after. "Sit0 is a device that's used to tunnel IPv6 through an IPv4 connection", not sure if you knew that or if that'll help you..

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Ah ok, no wasn't aware.

May point to a driver or udev issue then if that's the only other interface showing bar loop back.

I'm removing sit from the kernel and rebuilding at the mo, will keep you posted!

Yeah that has to be the problem

Ok so removed sit from the kernel and the sit0 interface has buggered off as expected.

Now I only have the lo interface.

lspci shows the nic

I've recreated the /etc/udev/rules.d/70-persistent-net.rules but running /lib/udev/write_net_rules with the correct mac address and eth0 as the interface name.

ip link and ifconfig only show the lo adapter?!?

oh and I also modified the /etc/sysconfig/ifconfig file to match the new interface name

Maybe check to see if networking is enabled in your VM's BIOS (Hyper V has a BIOS if im not mistaken), beyond that I couldn't tell ya.. Just Google around for how to bring eth0 back, im sure you'll get it working..

Finally got it working!

Was a missing driver after all that should of googled what sit was to start!

Even re-enabled sit on the kernel and I'm able to pass traffic perfectly!

Many thanks for your help linux4evr5581