Question: I have two devices in the same broadcast domain. My PC and an Avaya IP Control Unit.

My IP is **10.168.10.154/22**.

Avaya Device IP is **192.168.10.99/23**.

I am able to ping this device and don't understand how.

1. The Avaya Device has no gateway set.
2. Even if it did, there are no routes on the Cisco router to any **192.168.x.x** networks. The switches all have L3 functions turned off.
3. The MAC Address shown from "arp -a" on my PC is the same MAC Address shown in the MAC Address Table of the switch the Avaya Device is connected to. So I think I can safely assume there is no ARP Proxy.
4. Route Print on my local machine shows: **192.168.10.99 255.255.255.255** On-link **10.168.10.154** 26
5. Tracert shows: Tracing route to **192.168.10.99** over a maximum of 30 hops

1 \* 1 ms <1 ms **192.168.1.99**

Even more odd, my PC seems to be the only device that can ping the Avaya device. My PC has one physical interface, and it has no sub-interfaces. There is a virtual inteface created by VirtualBox, but it resides in the 192.168.56.0/24 network so I'm not sure it's relevant. Possibly worth mentioning is that this is a MacMini running Bootcamp, so maybe this is a function of Bonjour?

Answer: 
> 
> Route Print on my local machine shows: 192.168.10.99 255.255.255.255 On-link 
>  10.168.10.154 26
> 
> 
> 

That is why, the On-link routes are accessible locally without any gateway, many times they are created when you connect via dial-up (to Avaya device maybe). You have to find out why this route is being created. Maybe it was just a left over or was added manually in the past as a persistent route, Try deleting the route, ping, then reboot and ping to see it was not created again somehow.
It looks to me like you have an additional ip address assigned to your NIC.

[![enter image description here](https://i.stack.imgur.com/ItJ0x.png)](https://i.stack.imgur.com/ItJ0x.png)

[![enter image description here](https://i.stack.imgur.com/zktPU.png)](https://i.stack.imgur.com/zktPU.png)