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stony
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3 AP´s one Net

Tue Nov 11, 2008 2:50 pm

Hallo

I have following configuration:

<HP -Switch>
| | |
AP AP AP

The AP are RB433 with one active Ethernet and one WLAN.
The client´s (Scanner Symbol 9090) are the clients. We have the problem, when a client change the connection from an AP to another AP we can not ping these client. When the client send any traffic the ping works again.

So, we want to create a WDS. But I have same problem with this configuration.
1) Must all AP´s connect to the switch about the Ethernet-Interface or only one.
2) Must I add the Ethernet-Interface to the bridge interface.
3) Are there MASTER AP and SLAVE AP.

regards
manfred
 
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Re: 3 AP´s one Net

Tue Nov 11, 2008 9:09 pm

I do not think WDS is the way to go in your case, because WDS is a way how to wirelessly connect one AP with another, but this is not necessary in your case because all APs are connected over Ethernet.

You should give more information about APs setup, but I assume that on APs ethernet interface is bridged with wlan interface, right? Then first thing to suspect would be that after switching APs ping is still going over previous path because bridges have not got chance to update forwarding tables. As soon as client transmits a packet, bridges immediately learn that particular client is reachable over different port and ping starts working.
 
stony
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Re: 3 AP´s one Net

Tue Nov 11, 2008 9:57 pm

Yes, all AP has a bridged interface which include the ethernet and the wlan interface.
Can I can only connect on AP to the switch and the other AP´s connect about the WLAN.
How can I make one WLAN-Cloud so this ping does always works. Or is this not possible.
 
Mplsguy
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Re: 3 AP´s one Net

Wed Nov 12, 2008 11:12 am

There are several solutions that might help, but each comes with its drawbacks so you should seriously consider if its worth it - wether ability to ping client really matters, because as soon as client will start using network everything will work as expected.

1. When client roams (pings start failing) flush ARP cache on device that is sending ping into switch (e.g. router connected to switch or pinging computer if it is connected to switch) - on next ping ARP request will be broadcasted (flooded to all APs) and response will update switch forwarding table.

2. Decreasing ageing time (bridges/switches delete mac address from forwarding table no packet is forwarded to this mac address for ageing time - next packet to this mac address will be flooded to all ports) for HP switch. For this your switch must support configurable ageing time. Just take into account that decreasing this timeout (according to 802.1d std default is 30 seconds, min 10 seconds) will probably cause more unnecessary flooding in network. Also min of 10 seconds (or less, if your HP switch supports that) might not satisfy you.

3. Connecting APs physically (or logically) this way: switch-AP1-AP2-AP3. In this case switch will always forward data to AP1. Routeros is building bridge forwarding table for WLAN links not dynamically but based on who is connected, so as soon as client will disconnect from one AP, it will get deleted from bridge forwarding table and not sit there until ageing timeout.
 
stony
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Re: 3 AP´s one Net

Wed Nov 12, 2008 11:57 am

To 3)
Can I connect the second and third AP to the first about the WLAN.
 
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Re: 3 AP´s one Net

Wed Nov 12, 2008 2:49 pm

Yes, you can connect APs over wireless with WDS, but take into account that e.g. when sending frame from switch to client that is connected to AP3 (in setup switch-AP1-AP2-AP3) it will be sent over the same wireless channel 3 times and therefore max throughput will be 3 times lower. If that is fine, you can do this.

Otherwise you can consider setup with VLANs (if your switch supports that) and achieve basically the same 'logical" setup.
 
tlkhorses
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Re: 3 AP´s one Net

Fri Nov 14, 2008 1:51 am

Put one more routerboard in front of the switch. Bridge the three APs to it.

tk
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Mplsguy
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Re: 3 AP´s one Net

Fri Nov 14, 2008 4:36 pm

Unluckily this will not help, because this way problem will only be moved from switch to that new routerboard, as it will behave exactly the same way as switch.
 
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Re: 3 AP´s one Net

Fri Nov 14, 2008 7:09 pm

more then likley you are either not bridging wlan1 and ether1 on one or more of the APs, thus each AP is it's own seperate network, or you may have default forward disabled (I only skimmed your post)

make sure all wlan's are bridged to their respective ethernet interfaces (and don't run more then 1 DHCP server either, that will cause problems) and ensure default forwarding is enabled on all APs

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