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Re: Anycast applicable to Radius Server Farm ?
Joe Shen wrote:
I dont think its true. If the auth radius server fails to respond, authentication and accounting will then go to the next configured serverCan you indicate in more detail what the problems
See if you can extract load from the radius server using snmp or something and make your l4 switch utlilize that.So, although L4 switch provides a single IP for BRAS configuration each BRAS is specified a real server IP in L4 switch. So, there comes the problem: 1) Load is not balanced automatically but by human estimation; there is server whose load is twice of some other server.
2) L4 switch becomes bottleneck of service
Add a couple of the actual servers IPs to the aaa servers the NAS's use
Your firewalls should be protecting your radius servers from DoS -- unless you really expect the world to communicate with them. Spoofed sources however could be hard to protect against.3) As L4 switch is the only entrance to a single server farm, DoS attack or some other kind of software bug will surely degrade security level. While, a farm using ECMP rely on server groups to resist DoS attack.
Let the nas do it. they fail over much faster than that.4) Maintence is a little bit costy. Any maintence , no matter on radius server or on L4 switch, need a scheduled time window. 5) Service protection is hard ( as you mentioned as 'cascade' one). As there are two server farms, if one farm failed it takes ten or more minute to migrate those Radius traffic to the other farm. This is unacceptable.
Whatever you choose, try to combine the ability of the nas to failover radius servers into your redundancy plan.