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Device does not respond to ping from other subnets #196

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pstavirs opened this Issue Sep 15, 2016 · 0 comments

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pstavirs commented Sep 15, 2016

Reported by Bobby Smith via this post on the mailing list -

I am seeing a problem with IPv4 device emulation in Ostinato v0.8 when routing reply traffic via a default gateway to remote DUTs. I know this is a new feature so not 100% sure if this is user error, expected behavior, or a bug.

Here is a detailed description:

IPv4 emulated devices do not respond to non-local, DUT initiated traffic.

In the following diagram:

OA = Ostinato Agent (with 5x IPv4 emulated devices on local subnet A and default gateway correctly set)
DG = Default Gateway (router with interfaces in subnets A and B)
DUT = Device Under Test (in subnet B – i.e. the remote subnet)

OA-------(subnet A)-------DG-------(subnet B)-------DUT

If we ping the emulated devices from DG on the local subnet A we see replies
If we ping the emulated devices from DUT on remote subnet B we don’t see replies

I have confirmed that the default gateway’s ARP entry on subnet A is correctly resolved within the emulated devices information window.

I have also run a packet capture on the Ostinato agent. I can see packets arrive from the DUT but no reply is sent. It would seem the IP stack on the emulated devices is not correctly using the default gateway to reply to remote traffic.

However I have noticed: If I create a stream from the emulated devices on subnet A to a DUT on remote subnet B and I use the “resolve” option for source and destination MACs then the IP stack correctly sends Ostinato initiated traffic via the default gateway.

Logs and capture file attached corresponding to steps taken:

  1. Added 5 emulated devices: 172.16.100.11-15 with gateway 172.16.100.1
  2. Clicked "Resolve Neighbors" in GUI (see packets 2 - 11)
  3. Sent 5 pings from local subnet gateway router IP 172.16.100.1 (see packets 12 - 21). This worked fine
  4. Sent 5 pings from remote subnet gateway router IP 172.16.200.1 (see packets 22 - 26). This didn’t work

Looking at the log, I guess the fun starts with

sendIp4Reply: mac not found for 172.16.200.1; unable to send IPv4 packet

log.txt
cap.pcapng.gz

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