Kernel Debug with dbgsettings {dhcp no} option, host & target PC connected to sperated network switchs but under one core switch

WINDBG
1

Hi there, i have met an issue with kernel debug as title. I will descript more detail below. Please help take a troubleshooting, thanks!

  1. One Host PC, one target PC with kernel debug supported NIC.
  2. Two Cisco switch stack, host PC network cable connect to Stack 1, target PC network cable connect to Stack 2.
  3. Target PC set dbgsettings to host PC's static ip address & ports & key.
  4. Target PC set dbgsettings with dhcp option no.
  5. Two cisco switch stack connect to the same core switch.
  6. This vlan with no dhcp server, host PC's network adpter set to static ipv4 address, Target PC's kernel debug adpter set to static ipv4 too manaully.
  7. Host PC & Target PC can ping each other after setting the static ip address.

With above enviroment set-up, the host PC can't use windbg connect to target PC.

However, if i put them in the same Cisco Stack, it's working fine.

I'm reference microsoft document:

here is the explaination: "KDNET on the target computer attempts to use Dynamic Host Configuration Protocol (DHCP) to get a routable IP address for the network adapter that's being used for debugging. If KDNET obtains a DHCP-assigned address, then the target computer can be debugged by host computers located anywhere on the network. If KDNET fails to obtain a DHCP-assigned address, it uses Automatic Private IP Addressing (APIPA) to obtain a local link IP address. Local link IP addresses aren't routable, so a host and target can't use a local link IP address to communicate through a router. In that case, network debugging will work if you plug the host and target computers into the same network hub or switch."

If i set dhcp option no, i suppose i'm in satuation two. Use APIPA to obtain a local link ip address & it's un-routable. If i put both PC in one cisco statck, it's working. If i put in seperate stack, it's not working. But for the above point 5, the two stack is connect to one core switch. I think APIPA address is working in mac level, not require routing. This is my confusion. Please help me solve it. Thanks!

3

@Tim_Roberts ,could you please give some advices, thanks!

4

I don't think I have anything to add. If you have assigned static IP addresses to both sides, then the APIPA stuff doesn't apply. APIPA addresses are in the 169.254.xxx.xxx range and are not routable.

5

Thanks，what if I didn't assigne a static IP for the kernel debug NIC, just let it obtain with APIPA address. Is that possible to connect the target PC from a different cisco switch? Both of the host PC & Target PC are connect to each cisco switch stack under one core switch.

6

I already told you that, and you read it in the documentation. If you don't assign an address and don't get one from DHCP, the system picks an APIPA address in the 169.254 range, and those ranges are not routable. They will not cross subnets.