Recently, I help my sibling company to setup HSRP configuration
1 Cisco 2921 connecting 2 Cisco 3650.
It works normally without any problem at the very beginning.
Later, user reports that Windows 2008 report duplicate IP after rebooting or re-enable network adapter.
After a serious a research, I got the following findings.
1. ping to unused ip address will got TTL expire.
2. traceroute to unused ip address will loop between that 3 Cisco device.
3. all unused ip address in Cisco 3650 arp table will map to ether-channel mac address.
After digging a 2 weeks about this problem, finally I found an article on the web. It said Cisco has made some changes on IOS after 12.8 which I need to add "no ip proxy-arp" on both 3650 uplink to 2921.
