From my experience and knowledge of OSPF (I am not an expert, but have
read a lot and have over 700 devices on the network running OSPF) this
is to be expected. There is no OSPF cost difference in the route to the
AP and to the other tower. From Tower A the cost to the AP is the same
as the cost to the other tower.
You may be able to "fix" it by disabling inter-client communication on
the AP wireless interface.
You may be able to "fix" it by creating a virtual interface on the AP
wireless interface and using a different subnet on that virtual
interface. Then the cost from remote tower to AP is less than the cost
from remote tower to remote tower.
You may also "fix" it by setting the router IDs so that the AP gets
elected as the Designated Router. I don't recall if MT uses the highest
or lowest ID, but one of them has preference as DR.
Honestly, my opinion is the best fix is to use two PTP links to get to
the 2 towers and put them on separate subnets. Since all the traffic
for both towers goes in and out one interface, there is a bandwidth
limitation for each tower. Troubleshooting gets easier with
separation. A single radio failure only takes down one tower instead of
2 towers. I realize there are lots of valid reasons to share the AP,
but one of my network design criteria is to not share backhaul links
between towers.
On 2/26/2014 6:21 AM, Paul McCall wrote:
This network is routed. We have this scenario a few places in our network but
this is the only section not working.
A Single AP (single interface) connects to SMs at multiple towers to be their
primary (lowest cost) path to the internet. All on the same subnet. We have
as many as 5 towers fed like this from a single AP/single subnet/single OSPF
network.
This particular AP feeds 2 towers. One of the "fed" towers works as expected, always going to the
"AP" tower. The other "fed" tower jumps to its "brother" instead of the AP tower.
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Scott Reed
Sent: Wednesday, February 26, 2014 6:08 AM
To: Mikrotik discussions
Subject: Re: [Mikrotik] OSPF "problem" situation #1
If I understand what you are saying correctly, then I must ask, is this a
bridged/switched network or a routed network.
If it is bridge, you are not going to get OSPF to do what you want as there is no
"shortest" path from a routing point of view.
If it is routed, then it should work. OSPF does things by interface, so if you
have 2 towers being fed from a single interface, it doesn't know how to
determine which interface to use as there is only one.
Please give us some more information about the total topology that you have.
Topology is critical in knowing how to setup the OSPF parameters.
On 2/25/2014 7:38 PM, Paul McCall wrote:
Costs are all set right, both incoming and outgoing. The problem is
that the TIK does not seem to differentiate between the two towers
that it could possibly go to because they are on the same subnet and
same OSPF network. That's the problem, in a nutshell
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Scott Reed
Sent: Tuesday, February 25, 2014 6:21 AM
To: Mikrotik discussions
Subject: Re: [Mikrotik] OSPF "problem" situation #1
Not sure what you have setup, but a couple of things come to mind.
A router ID on any router of 0.0.0.0 will cause funny things to happen
occasionally. Make sure all routers have an unique ID.
Routes with equal costs will sometimes change. Make sure you have the costs
setup correctly on the routers. Make sure the cost is the same for both
directions on a link unless you really do want traffic to use a different path
inbound than outbound.
More specific routes have priority over more general routes. Not everything
takes the default route, if there are other ways to get somewhere.
There have been some issues with some levels of UBNT firmware. If you are a
WISPA member, check the archives on the mail lists. (If you aren't a WISPA
member, get signed up as soon as you can.) If you want help offlist, feel free
to e-mail me directly.
On 2/24/2014 2:34 PM, Paul McCall wrote:
Tower A has a Rocket M5 feeding Tower B (as its primary OSPF path)
and Tower C (as its secondary OSPF Path and that works correctly)
Seemingly since A (xxx.xxx.214.49), B (xxx.xxx.214.50) and C (xxx.xxx.214.51)
are on the same subnet and the same OSPF network, sometimes Tower B will go
through Tower C before going to Tower A.
Even with a static route from B (214.50) to A (214.49), the OSPF default route wants to
prefer the tower C (214.51) path. In the IP, Route List it shows that the default
should go the right direction with a "distance" of 1. In the OSPF, Routes it
shows Tower C (214.51) as the default path with a cost of 1 and a state of Ext 2.
Any thoughts ?
Paul McCall, Pres.
PDMNet / Florida Broadband
658 Old Dixie Highway
Vero Beach, FL 32962
772-564-6800 office
772-473-0352 cell
www.pdmnet.com<http://www.pdmnet.com/>
[email protected]<mailto:[email protected]>
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--
Scott Reed
Owner
NewWays Networking, LLC
Wireless Networking
Network Design, Installation and Administration Mikrotik Advanced
Certified www.nwwnet.net
(765) 855-1060 (765) 439-4253 Toll-free (855) 231-6239
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RouterOS
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Checked by AVG - www.avg.com
Version: 2014.0.4335 / Virus Database: 3705/7124 - Release Date:
02/25/14
--
Scott Reed
Owner
NewWays Networking, LLC
Wireless Networking
Network Design, Installation and Administration Mikrotik Advanced Certified
www.nwwnet.net
(765) 855-1060 (765) 439-4253 Toll-free (855) 231-6239
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-----
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2014.0.4335 / Virus Database: 3705/7124 - Release Date: 02/25/14
--
Scott Reed
Owner
NewWays Networking, LLC
Wireless Networking
Network Design, Installation and Administration
Mikrotik Advanced Certified
www.nwwnet.net
(765) 855-1060 (765) 439-4253 Toll-free (855) 231-6239
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