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rmatousek
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PCC load balancing issue

Fri Apr 09, 2021 1:06 am

Hi, I have implemented PCC load balancing as explained in example 3 here: https://help.mikrotik.com/docs/display/ ... ll+Marking. I have swapped IP addresses and I am using interface bridge instead of ether3 as I use my RB4011iGS+ to directly connect my home appliances. The setup seems to be working from the bridge network and all connections are properly marked in the IP/Firewall/Connections list (except for those starting and terminating in the bridge address range).

I wanted to experiment with scripting/netwatch to disable unreachable routes, but unfortunately, it seems that I cannot ping 8.8.8.8 from the router itself. I get "no route to host" error. I have also noticed that WinBox shows IP->Routes->NextHops Gateway state "Unreachable". Ping from devices connected to the bridge interface works properly.

Any idea what is going on here? Is the tutorial missing some rules to handle this particular example, or I have misconfigured something?
 
rmatousek
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Re: PCC load balancing issue

Sat Apr 10, 2021 6:32 pm

I should also add that my ROS is v7.1beta5.

I am doing some research and when I use the traceroute tool from WinBox, I get timeouts. When I configure the traceroute to use the routing table "to_ISP1", or "to_ISP2", the traceroute works ok. Unfortunately, I cannot figure out what firewall rules get applied to the ICMP packets created on the router.

Is there an easy way how to visualize the packet journey through the router? I.e. what chains it has traveled through and what rules did match there?

Thx.
 
rmatousek
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Re: PCC load balancing issue

Sat Apr 10, 2021 9:10 pm

Ok, so after studying the Packet Flow https://help.mikrotik.com/docs/display/ ... n+RouterOS and watching this great conference presentation https://youtu.be/MF0lGclPa5E?t=822 on "Understanding packet flow in ROS6", I have a bit of more understanding of how it works.

I see that all packets created in the ROUTER PROCESSES (I assume ping/traceroute/netwatch are router processes) reach the ROUTING DECISION first, then pass the OUTPUT and POSTROUTING chains and leave the box via the physical interface.

Knowing the fact that example 3 at https://help.mikrotik.com/docs/display/ ... ll+Marking does not configure any route, nor match any OUTPUT rules for connections created by the router itself, I guess that broken ping is not a bug, but the feature of this setup.

Can you please confirm that my investigation is correct? If yes, I assume that example 3 cannot use the check-gateway=ping option as any ICMP packet created by the router will fail.
 
pe1chl
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Re: PCC load balancing issue

Sat Apr 10, 2021 9:18 pm

It is always advisable to have a route for unmarked/unhandled packets, even when it is always via the same internet connection.
E.g. you make one or two default routes in the main table, and make additional tables that have the route via one of the providers (and fallback to the other) in additional tables.
In fact you need only main and one additional table to implement this for two providers.
Then you never get in the situation that you have no route for packets because they are not marked with a route preference.

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