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RB2011 switch configuration, groups, external interfaces

Posted: Tue Nov 07, 2017 4:29 pm
by DF4OR
I have a problem understanding the correct switch configuration of an RB-2011 router. The model is RB2011L with two ATheros switch chips, one Ath8327, one Ath8227.

I need 5 routed ports, two switched ports. All need to talk to each other.

The docs at ... p_Features quite clearly says "Interfaces for which the 'master' port is specified become inactive - no traffic is received on them and no traffic can be sent out." But the drawings on the same page further down all show the master ports, which are member of the internal bridge, also als present on the physical interface, just like any other port. A short test showed at least some packet count on such a master port in my current test setup, when a cable is connected to that physical port. Unfortunately I cannot do more testing at the moment for reasons beond the scope of the post.

My questions
1.) Is a port, which is master for a switch group, also useable at the same time on the physical interface or not?
2.) Can a master port be a member of the internal bridge at the same time?
3.) Is there a penalty to using an internal bridge? I read in another thread here that there is a performance slowdown if using internal bridging.
4.) Could I do without the internal bridge at all? Why not just use a cable from one switch group to the other? This would somewhat be simpler, wouldn't it?

If a physical port becomes indeed unuseable because they are a master port, I need to tie the two switches somehow together to have 5 physical routed ports. What would be the best way to do so? Any hints appreciated.


Re: RB2011 switch configuration, groups, external interfaces

Posted: Tue Nov 07, 2017 4:48 pm
by stoser
In response to your questions, based on my experience and understanding (I have 2 different 2011 routers, and 3 different 3011s, which function similarly)

1) The master port is usable. The master and all slaves will function as a standard switch. You can have up to 5 ports on each of two switch groups on the 2011, two switch groups in total. One will be Gb, the other fast ethernet.
2) Yes. That is the standard way to bridge switch groups. The master port and all of its slave ports will be joined to the bridge. It would be like connecting an external switch to a port on the 2011 that is part of the bridge
3) There is a big penalty for using the internal bridge. The bridge is a software bridge, so everything must be processed my the CPU. In switch mode, a dedicated switch chip handles the switching (much faster)
4) You can cable the two switch groups together. I am currently doing that, as I only needed <= 4 ports on each switch. Bridging the two master ports on the switch groups would give you a performance penalty, but you could have 5 physical ports on each switch group.

Hope this helps.

Re: RB2011 switch configuration, groups, external interfaces

Posted: Tue Nov 07, 2017 4:58 pm
by stoser
Also ... I just read the page that you referenced ... I now see why you are confused. "Interfaces" does not refer to physical ports. It refers to interfaces that can be referenced in the command line, winbox, etc. So any configurations that you apply when you have a switch group MUST reference the MASTER port.

When the manual states "Interfaces for which the 'master' port is specified become inactive" it is referring to the slave ports (it is on the slave ports that you specify the master port). The MASTER port is actually the only port in the switch group with "none" specified as the master port (this implies that it is its own master).

A bit confusing, now that I think about it, but hope this helps