CARP - Not able to access the LAN IP of the Backup pfSense machine



  • Hello,

    I am running 2 WatchGuard XTM Series machines as my pfSense master and backup machines. I currently have CARP setup, but is unable to ping or access the LAN IP of the backup pfsense box (10.1.1.3) from my 192.168.1.0 subnet. I am using a transit vlan (10.1.1.2) to access the pfsense master and backup machines. From the 192.168.1.0 subnet, I am able to ping and access the pfsense master PC (10.1.1.1) and the LAN virtual IP (10.1.1.6). From my layer3  switch in my internal LAN network, I do have a static route to the LAN virtual IP (10.1.1.6).

    What setup is missing on my pfsense backup machine? Attached is a drawing of my network.



  • You can't reach the backup directly from 192.168.1.0, packets must be routed over the master, cause the static route point to the LAN VIP. This is also true for responses from the backup.

    To get this work the best way is to add an outbound NAT rule to the master, translating packets destined for the backup to the LAN address.
    To get this work independently which one is the master, add an host alias including the two LAN addresses of master and backup.
    Then add a new outbound NAT rule (outbound NAT must be set to manual or hybrid rule generation mode), select the LAN interface, at source enter 192.168.1.0/24, at destination select network an enter the alias you've added first, you may also restrict the rule to the specific dest port and at translation address select interface address.

    If you have rule sync on this rule will be synced to the backup and will also fit in case if this one is the master.



  • @viragomann:

    You can't reach the backup directly from 192.168.1.0, packets must be routed over the master, cause the static route point to the LAN VIP. This is also true for responses from the backup.

    To get this work the best way is to add an outbound NAT rule to the master, translating packets destined for the backup to the LAN address.
    To get this work independently which one is the master, add an host alias including the two LAN addresses of master and backup.
    Then add a new outbound NAT rule (outbound NAT must be set to manual or hybrid rule generation mode), select the LAN interface, at source enter 192.168.1.0/24, at destination select network an enter the alias you've added first, you may also restrict the rule to the specific dest port and at translation address select interface address.

    If you have rule sync on this rule will be synced to the backup and will also fit in case if this one is the master.

    I'm somewhat new to pfsense so please be patience with me. Based on your comments there are 2 options. It looks like you are recommending the last option. If yes, can you provide more detail steps.

    Thanks.



  • No, I suggested only one solution.
    With this outbound NAT rule the source address of packets which are destined to the other pfSense box will be translated to the pfSense LAN address when they are going out the LAN interface. This way responses to these requests are directed back to the other pfSense.

    To set this up
    add an IP alias in Firewall > Aliases > IP. Enter a name (e.g. FW1a2), type = "Host(s)", at hosts below enter the masters LAN IP 10.1.1.1 at IP and a description beside, click "add host" and enter the LAN IP of backup 10.1.1.3 and a description.

    Got to Firewall > NAT > Outbound. Ensure that the rule generation mode is set to manual or hybrid.
    Add the suggested NAT rule:
    Interface: LAN
    Protocol: TCP
    Source: Network <the alias="" name="" you="" have="" set="" up="" first,="" e.g.="" fw1a2="">Destination: Network 192.168.1.0/24
    Address: Interface address
    Enter a description below and save the rule.

    That's it. Hope, it's a bit more clearly now.</the>



  • @viragomann:

    No, I suggested only one solution.
    With this outbound NAT rule the source address of packets which are destined to the other pfSense box will be translated to the pfSense LAN address when they are going out the LAN interface. This way responses to these requests are directed back to the other pfSense.

    To set this up
    add an IP alias in Firewall > Aliases > IP. Enter a name (e.g. FW1a2), type = "Host(s)", at hosts below enter the masters LAN IP 10.1.1.1 at IP and a description beside, click "add host" and enter the LAN IP of backup 10.1.1.3 and a description.

    Got to Firewall > NAT > Outbound. Ensure that the rule generation mode is set to manual or hybrid.
    Add the suggested NAT rule:
    Interface: LAN
    Protocol: TCP
    Source: Network <the alias="" name="" you="" have="" set="" up="" first,="" e.g.="" fw1a2="">Destination: Network 192.168.1.0/24
    Address: Interface address
    Enter a description below and save the rule.

    That's it. Hope, it's a bit more clearly now.</the>

    Got it… One clarification. On the NAT Outbound, please confirm the source and destination. Your first post seems to be different than your last post.

    Once again, thank you so much.



  • Sorry, that was a mistake.
    It should be
    Source: Network 192.168.1.0/24
    Destination: Network <the alias="" name="" you="" have="" set="" up="" first,="" e.g.="" fw1a2="">of course.</the>



  • @viragomann:

    Sorry, that was a mistake.
    It should be
    Source: Network 192.168.1.0/24
    Destination: Network <the alias="" name="" you="" have="" set="" up="" first,="" e.g.="" fw1a2="">of course.</the>

    Does not seem to be working.. Do I need to specify anything in the "Translation Address" field?




  • "Interface address" is fine here.
    The alias contains both LAN addresses of master and backup?

    Please post a screenshot of the outbound NAT page.



  • @viragomann:

    "Interface address" is fine here.
    The alias contains both LAN addresses of master and backup?

    Please post a screenshot of the outbound NAT page.

    Here you go…






  • Well I got the LAN interface working on the pfsense backup machine.  It was the ports on my switch….

    Now I am troubleshooting the WAN interface on the pfsense backup machine. For some reason, I cannot ping the WAN interface (192.168.50.3) on the backup pfsense machine. I am able to ping the pfSense master WAN  IP (192.168.50.2) and the WAN Virtual IP (192.168.50.254) from the 192.168.1.0/24 subnet.. What in world is my problem?


  • LAYER 8 Netgate

    Why would you care about reaching the secondary's WAN interface in that fashion?

    It should work as long as there is outbound NAT out the primary's WAN. if not you will probably be looking at an asymmetric routing issue.



  • @Derelict:

    Why would you care about reaching the secondary's WAN interface in that fashion?

    It should work as long as there is outbound NAT out the primary's WAN. if not you will probably be looking at an asymmetric routing issue.

    Based on my setup, should I be able to reach the pfSense backup WAN IP (192.168.50.3/24) while the pfSense master machine is active and without an outbound NAT?

    I assume when the backup becomes the master, I should be able to ping the pfSense backup WAN IP (192.168.50.3/24).



  • Yes, it should be reachable if your WAN interfaces and the WAN VIP are in the same network segment and if the firewall rules allow the ping to WAN.



  • @viragomann:

    Yes, it should be reachable if your WAN interfaces and the WAN VIP are in the same network segment and if the firewall rules allow the ping to WAN.

    I am only able to ping the pfSense backup WAN IP (192.168.50.3) only when there is a failover and the pfSense backup becomes the master. The failover seems to be working fine. Just I cannot figure out this issue.

    You mentioned firewall rules and outbound NAT rules. Can you provide some detail on specific things to check..


  • LAYER 8 Netgate

    That is because when the secondary is CARP master it is the node that receives the traffic on the LAN CARP VIP. Again, what are you trying to prove by accessing the secondary's WAN interface from the inside when it is not CARP MASTER?

    Why did you X.X out the IP addresses on the WAN side in your diagram? Makes it pretty hard to communicate specifics back to you. They are RFC1918. Who cares about protecting/hiding them?

    Can you ping the secondary's WAN IP address from the primary? Then it's working.

    Can you ping the secondary's LAN address from LAN? Then it's working.

    Can the secondary resolve names, check for updates, and check for packages while it is NOT CARP master? Then it's working.



  • @Derelict:

    That is because when the secondary is CARP master it is the node that receives the traffic on the LAN CARP VIP. Again, what are you trying to prove by accessing the secondary's WAN interface from the inside when it is not CARP MASTER?

    Why did you X.X out the IP addresses on the WAN side in your diagram? Makes it pretty hard to communicate specifics back to you. They are RFC1918. Who cares about protecting/hiding them?

    Can you ping the secondary's WAN IP address from the primary? Then it's working.

    Can you ping the secondary's LAN address from LAN? Then it's working.

    Can the secondary resolve names, check for updates, and check for packages while it is NOT CARP master? Then it's working.

    Here is the diagram with the WAN IP addresses unmasked…




  • @Derelict:

    That is because when the secondary is CARP master it is the node that receives the traffic on the LAN CARP VIP. Again, what are you trying to prove by accessing the secondary's WAN interface from the inside when it is not CARP MASTER?

    Why did you X.X out the IP addresses on the WAN side in your diagram? Makes it pretty hard to communicate specifics back to you. They are RFC1918. Who cares about protecting/hiding them?

    Can you ping the secondary's WAN IP address from the primary? Then it's working.

    Can you ping the secondary's LAN address from LAN? Then it's working.

    Can the secondary resolve names, check for updates, and check for packages while it is NOT CARP master? Then it's working.

    I cannot ping the pfSense backup WAN IP address (192.168.50.3) from the pfSense master machine (see attachment).
    I can ping the pfSense backup LAN IP address (10.1.1.3) from the pfSense master machine (see attachment)






  • @Derelict:

    That is because when the secondary is CARP master it is the node that receives the traffic on the LAN CARP VIP. Again, what are you trying to prove by accessing the secondary's WAN interface from the inside when it is not CARP MASTER?

    Why did you X.X out the IP addresses on the WAN side in your diagram? Makes it pretty hard to communicate specifics back to you. They are RFC1918. Who cares about protecting/hiding them?

    Can you ping the secondary's WAN IP address from the primary? Then it's working.

    Can you ping the secondary's LAN address from LAN? Then it's working.

    Can the secondary resolve names, check for updates, and check for packages while it is NOT CARP master? Then it's working.

    I got it working.. On the WAN interface on the backup pfSense machine, I had to untick the "Block private networks and loopback addresses" and "Block bogon networks" options. See attachments.





Log in to reply