dual WAN, replies leave via incorrect interface

I am attaching tcpdump capture to make it more clear. Problem is, that packet arrives on Port4, but reply leaves on Port2 with address of Port4

18:57:54.312962 Port4, IN: IP 1.1.1.5.58206 > 2.2.2.2.500: isakmp: parent_sa ikev2_init
18:57:54.313435 Port1.26, OUT: IP 1.1.1.5.58206 > 192.168.1.50.500: isakmp: parent_sa ikev2_init

18:57:54.314053 Port1.26, IN: IP 192.168.1.50.500 > 1.1.1.5.58206: isakmp: parent_sa ikev2_init[]
18:57:54.314480 Port2, OUT: IP 2.2.2.2.500 > 1.1.1.5.58206: isakmp: parent_sa ikev2_init[]

Here is example of working connection, where source (5.5.5.5) is not in XG routing table.

20:29:17.155236 Port4, IN: IP 5.5.5.5.54196 > 2.2.2.2.500: isakmp: parent_sa ikev2_init
20:29:17.157140 Port1.26, OUT: IP 5.5.5.5.54196 > 192.168.1.50.500: isakmp: parent_sa ikev2_init

20:29:17.212375 Port1.26, IN: IP 192.168.1.50.500 > 5.5.5.5.54196: isakmp: parent_sa ikev2_init[]
20:29:17.213311 Port4, OUT: IP 2.2.2.2.500 > 5.5.5.5.54196: isakmp: parent_sa ikev2_init[]

For the dnat, are you using reflexive rule?

I wasn't so I did a quick test now by enabling it, and it doesn't help.

Martin,

create a policy routing:

https://community.sophos.com/kb/en-us/123579

I tried that yesterday already, but it didn't help(it had no effect).

Did you check the routing precedence?

https://community.sophos.com/kb/en-us/123610

its configured like this. I think the problem is, that route is Connected, not static. 

console> system route_precedence show
Default routing Precedence:
1. Policy routes
2. VPN routes
3. Static routes

Hi Martin Hlavaty 

This is expected behaviour in any linux based system.  Direct attached routes take precedence over everything.  As such, as your client is within the same WAN IP range as you, the XG will route the traffic out that particular link.

The permanent solution to this is to get in contact with your ISP and ask why they have assigned you a /24 public or larger IP range if you do not own these IPs.  The temporary workaround to this is to create a static route for the IPs you do not have access to/ownership of and route it out your WAN2 gateway.  This will allow the routing to take place.

Thanks!

Hi Martin Hlavaty 

This is expected behaviour in any linux based system.  Direct attached routes take precedence over everything.  As such, as your client is within the same WAN IP range as you, the XG will route the traffic out that particular link.

The permanent solution to this is to get in contact with your ISP and ask why they have assigned you a /24 public or larger IP range if you do not own these IPs.  The temporary workaround to this is to create a static route for the IPs you do not have access to/ownership of and route it out your WAN2 gateway.  This will allow the routing to take place.

Thanks!

Thanks for the info.

Yes my wan and my customer's wan in same subnet. Solution would be to switch to separate /31 and let ISP's router to route it instead of having shared subet for multiple customers (probably to spare few IPs).