Carlos Bordon <cgermanb@live.com.ar> wrote:
I have ine server with freeradius, other with dhcp and they are connect to cisco 6800 swicht. We aunthenticate the endpoint with mab, because we cant use 802.1x. the problem that i want to resolve is to mitigate mac spoofing on layer two. For us is the same mitigate the problem on the radius or the swicht config.
With MAB there is absolutely no way to tell if the host using a MAC address is the actual host that has that burned-in-address (BIA). There are a few things you can do. First, use IP DHCP snooping and ARP inspection features on the edge switch. This will at least keep one host from spoofing many IP or MAC addresses without doing a DHCP transaction for each address, which slows an attacker down. You can also use edge switch port security features to limit the number of MAC addresses allowed on a single port to something reasonable. (While you are at it, see if you also have features to prevent DHCP starvation.) The second thing you can do is on the FreeRADIUS side, which is to use a Simultaneous Use database to prevent MAB requests from different ports at near the same time from being accepted. However, this can be problematic. If you are updating the Simultaneous Use database based on edge switch Accounting packets, then the edge switch may leave stale sessions open and continue to send updates after a host is unplugged and moved by the user to another port... especially if a minihub has been attached to the network and the link stays up. Then when the user gets to the place they have moved, they cannot get on the network because Simultaneous Use thinks they are an imposter. You have to check the behavior of your edge switches and do a lot of testing to make sure that this will work without problems. - List info/subscribe/unsubscribe? See https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.freeradius.org%2Flist%2Fusers.html&data=02%7C01%7Cbjulin%40clarku.edu%7Cde5fbe120aad4dc42cb908d68d385551%7Cb5b2263d68aa453eb972aa1421410f80%7C1%7C1%7C636851670434206702&sdata=3LeffAboqhJgk5s%2Brs7hJav0ZZ47RNF6C3juRjRj%2BS8%3D&reserved=0