Traffic is going through wrong interface from VLAN - BGP

[s4nguine]

Hello,

I have a weird issue, but maybe you will be able to point me in the right direction, I feel like I'm running in a circle.
My setup contains several VLANs, but I'll limit my issue to only 3.

1. VLAN99 - range 172.31.0.1/24 - tag 99
2. VLAN20 - range 172.31.20.1/24 - tag 20
3. VLAN30 - range 172.31.30.1/24 - tag 30

I'm testing the connection from address 172.31.20.209 which is in VLAN20. This host has a rule to allow all.
VLAN20 and VLAN30 have dedicated pools in DHCP which I'm using for Kubernetes load balancer purposes.

LB address 172.31.30.101 (VLAN30) works perfectly fine, I'm able to reach the service.



LB address 172.31.20.222 (VLAN20) on the other hand is blocked on the firewall, and traffic looks wrong. I'm struggling to find any meaningful difference between those VLANs, they were configured pretty much the same.
It's important to say that when I disable the firewall it works. Can you possibly point me in the right direction as to why it might be leaving from the wrong interface?



Thank you in advance

[s4nguine]

Sorry, I'll allow myself to bump it with a new post since I found out the most probable cause.
I didn't know it was relevant - I'm using BGP to announce addresses from the Kubernetes cluster.
It is exposed on address 172.31.0.8 - which is on VLAN99 so it makes sense why it leaves through it's interface.

The question is how can I modify it?

I would want that when network is from 172.31.40.1/24 range it picks VLAN40 interface. Is it doable?