Simple Load Balancing, two routes with equal cost

RouterOS Forwarding Protocols
1

If two routes have equal cost will OSFP automatically load balance across them?

Imagine a diamond shaped network, and packets want to go from HOME base to SECOND BASE, but can go through
either FIRST base or THIRD base both of which have the same cost.

What will the outgoing packets do wanting to go from HOME to SECOND?

What will the return packets do, from SECOND TO HOME?

Thanks in advance

Homer W Smith
CEO Lightlink Internet

2

Hmmm… Routes with equal costs (ECMP routes) may appear as result of OSPF. But may be created manually.
In any case OSPF doesn’t do any balancing itself - it just “creates” and chooses routes between source and destination points.
In the case of ECMP route (doesn’t matter - OSPF produced or manually created) usual ECMP route behavior is applied.
If I remember right router randomly chooses gateway from available in the ECMP route.
Balancing is per connection i.e. if packets from point 1 started going to point 2 via gate1, all other packets for this connection will go via gate1 in both directions.
Connection in the Mikrotik is src-address+src-port+dst-address+dst-port.
But every 10 minutes (again if I remember right) connections in the connection tracking table are resetting i.e. possible situation when first 10 minutes packets going via gate1 , next 10 minutes via gate2 and so on. Also it is possible situation when http traffic between same two points will go via gate1, https or ftp - via gate2.
Also possible problem with some protocols like SIP. For them either protocol helpers should be switched on or other methods applied.
If you need something other - you should try other methods from
http://wiki.mikrotik.com/wiki/Load_Balancing
For example, PCC or bonding…

3

Thank you for your response, I have and will again check out the link.

The issue I believe it not load balancing per se, but simply whether OSPF will round robin the packets or connections across the two equal cost links. I take it from your answer that it will.

What I don’t understand is how the default gateway is handled at the remote end, as the remote single router has only one
static default gateway, so although the packets from the internet going through the first router will split along the two lines to the second router, the return packets will always take the second routers default gateway back.

I want the packets to come back the way they went.

I guess I am looking for an EASY OSPF solution to that, unless OSPF just can’t do it, then we go to more complicated things in the link you provided.

Thanks for your time,

Homer W. Smith CEO
Lightlink Internet

4

I want to know if ospf cand double bandwidth?