Share via

Windows server routing changes ICMP source addr

ScooterOC 1 Reputation point
2022-10-20T22:49:08.673+00:00

My simple network consists of Linsys router, hyper-v host with 5 virtual networks in 172.16.0.0/16 CIDDR space. I am trying to connect to VMs in one of the five hyper-v virtual networks, 1721.16.21.0/24 from a physical Win11 computer on my 192.168.1.0/24 network.

Hyper-v host IP address is 192.168.1.12 and has five virtual networks:
172. 16.21.0/24, 172.16.20.0/24, 172.16.30.0/24, 172.16.42.0/24 and 172.16.86.0/24
IP Forwarding is enabled on all Hyper-v interfaces

I added static route 172.16.0.0/32 G/W:192.168.1.12 to the Linksys router and to the physical computer and I thought the static routes on router and the physical Win10 computer at 192.168.1.47 was all I needed to let me connect to VMs from my computer but not so quick.

To troubleshoot, I placed Wireshark on the physical computer at 192.168.1.47, the Hyper-v host (192.168.1.12) and the VM (172.16.21.10)

The VM receives the ICMP from 192.168.1.47 and returns the ICMP source 172.16.21.10 and destination IP 192.168.1.47.
When that ICMP packet gets to hyper-v, ICMP packet IP source is now 192.168.1.12 instead of 172.16.21.10 as expected.
I'd don't understand this topic well enough and hope to understand why the source address changed when it reached the vhost and how to configure OS to route correctly.

PS: I am not interested in RASS because I need packet routing, not NAT.

Windows Network
Windows Network
Windows: A family of Microsoft operating systems that run across personal computers, tablets, laptops, phones, internet of things devices, self-contained mixed reality headsets, large collaboration screens, and other devices.Network: A group of devices that communicate either wirelessly or via a physical connection.
756 questions
0 comments

1 answer

Sort by: Most helpful
Most helpful Newest Oldest
  1. Limitless Technology 44,336 Reputation points
    2022-10-21T15:30:54.823+00:00

    Hello there,

    Maybe you can use Traceroute, Ping, MTR, and PathPing network tools or utilities that use the ICMP protocol to perform testing to diagnose issues on a network and identify why the source changes.

    The TRACERT diagnostic utility determines the route to a destination by sending Internet Control Message Protocol (ICMP) echo packets to the destination. In these packets, TRACERT uses varying IP Time-To-Live (TTL) values.

    How to Use TRACERT to Troubleshoot TCP/IP Problems in Windows https://support.microsoft.com/en-us/topic/how-to-use-tracert-to-troubleshoot-tcp-ip-problems-in-windows-e643d72b-2f4f-cdd6-09a0-fd2989c7ca8e

    -------------------------------------------------------------------------------------------------------------------------------------------------

    --If the reply is helpful, please Upvote and Accept it as an answer–

    0 comments

Your answer

Answers can be marked as Accepted Answers by the question author, which helps users to know the answer solved the author's problem.