We have a location that has the need for about 500 ip host addresses. Our primary ip network is 172.20.1.0 To accomodate the additional IP addresses, I added a secondary ip address on the Ethernet interface of 172.20.11.0 This works well except for the fact that communication speed between the .1 and .11 subnet is extremely poor. Most of our servers are on the .1 subnet and some hosts on the .11 subnet have difficulty accessing applications on those servers because of the slow communication. I did expect some performance degradation considering the fact that I am routing between 2 networks, but what we are experiencing seems excessive. Copying files between hosts on the 2 different networks is many orders of magnitude slower than copying between hosts on the same network. Our backup server is on the .1 network and backing up/restoring to the .11 network is extremely slow. The router we are on happens to be a very OLD one (Cisco 3640) and that may play a role in causing this problem.
Are such network perfromance issues expected when using secondary ip addresses? Is the problem with the old router? Are there additional configuration changes I should make, such as using VLANS?
Any help would be appreciated.