BGP - how does it work when balancing?

Question

Border Gateway Protocol

Hello!
How does tcp/ip work when using bgp and two providers, splitting the /22 network into /24 networks and advertising them to different ISPs? On reception goes default.
Indeed, in this case, outgoing traffic is often proposed to be simply directed to one person by default, and a situation is obtained when outgoing traffic goes one way, and incoming traffic another. asymmetry in general.
Now it's done, it seems to work.
Is this normal and won't cause any problems in the future? Just just started testing such a scheme, it is not yet clear to the end.

Answer 1

Here it depends on how the task is.
If you need to balance traffic between providers, then you can’t get away from asymmetry.
On the other hand, firewalls are not very fond of asymmetry, and if such a firewall suddenly gets in the way of one of the halves of asymmetric traffic, it can kill the traffic.
To simplify possible debugging, I would recommend choosing one of the providers as the main one, the second one as the backup one, and worsen the announcements towards the backup one - either by extending the AS Path, or by giving more coarsely cut networks there. You can, of course, also play with MED ...
Inside your own network, to select the main path, again, you can look to the side:
- sawn in half default route (very cool and without additional gestures they will spread over IGP protocols, the same over OSPF)
- AS Path extensions on the backup link
- local preference