CARP/HA Source IP for Authentication is interface IP instead of CARP IP.



  • On my LAN side:

    Primary  = .63.98
    Backup    = .63.126
    CARP VIP = .63.1

    I have a Radius server at .63.230. I can't set the interface to use for calls to the Authentication server so when the authentication request goes out to my radius server, the source IP is the device IP (.98 or .126) instead of the VIP .63.1. I solve this problem by adding an outbound NAT rule on the LAN interface to map the device IP to the VIP without port translation (static port).

    Is there a more appropriate way to do this? Are there any problems it might create?



  • I usually just authorize the interface addresses for each firewall on the radius side. This means you can't sync the auth server from the primary to the backup, as the keys will be different.



  • Thanks for responding.

    That's a solution, sure. And the sync isn't a problem since the server authenticates the client by Shared Secret. The ideal solution is to be able to set the interface to use but that isn't an option.

    My question is if anyone can think of any problems my solution will cause given all requests to the LAN from the routers will have the source IP of the CARP VIP.



  • Ok, here I go answering my own question.  Bad idea!

    Using the outbound NAT for anything from the router broke dhcpd failover. The lease sync failed because the requests were blocked at the firewall by the default deny rule.

    So I guess I'll have to go with setting up two interfaces on the radius server.
    One more thing to have to remember.


  • LAYER 8 Netgate

    If you properly limit the scope of the outbound NAT to just RADIUS ports, it shouldn't touch DHCP. Limit the Destination to .63.230 ports udp/1812-1813 for instance.

    But I would tend to be in the "add the LAN interfaces for both nodes as RADIUS clients on the server" camp.



  • I agree, Derelict. I tend to be in that camp also.

    What I like about the NAT solution is it allows me to interchange a single router with an HA cluster without making changes to the rest of my network.

    Thank you for the answer on NAT.


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