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2 Separate ptp links on 2 Switches

Posted: Thu May 21, 2020 12:49 pm
by djboxny
Hello guys, i am trying to pass 2 ptp links to separate traffic between them. I have set up a vlan that i want it to go thru ether 3 to tower 3 and leave out the main line at tower 3 thru ether 1.

at the first tower on a mikrotik its added as a vlan of the ptp link comming to tower 2 thru ether 1. i cannot seem to get it to work at the last tower 4. vlan 3 is not working. maybe i am doing something wrong


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Tower 2
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Tower 3
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Re: 2 Separate ptp links on 2 Switches

Posted: Thu May 21, 2020 8:26 pm
by mike99
Seem fine. You should set IP address on vlan to check out until which device you ping.

To add an IP address, click on the gear just before VLAN tag/untag (etc) table.

Re: 2 Separate ptp links on 2 Switches

Posted: Thu May 21, 2020 10:20 pm
by Stephen
Also you may need to consider disabling STP. Or enabling MSTP.

Re: 2 Separate ptp links on 2 Switches

Posted: Thu May 21, 2020 11:36 pm
by djboxny
ok so i just disabled stp on ether3 (second ptp) and it worked beautifully Thank you guys.

Re: 2 Separate ptp links on 2 Switches

Posted: Thu May 21, 2020 11:38 pm
by djboxny
what is the difference in my scenario if i disable stp vs enabling mstp

Re: 2 Separate ptp links on 2 Switches

Posted: Fri May 22, 2020 1:17 am
by Stephen
STP is not VLAN aware, so when it is converging it looks at all ports and looks for a potential loop and doesn't know if some of those ports have been subdivided into VLAN's. Depending on the MAC address of the devices attached you might lose access to the management VLAN or one of the other VLAN's because all ports that could form a loop will be set to discarding except one.

MSTP is designed to use VLAN's but it requires that you tell it what VLAN's exist and on what ports so that it know's that a loop won't occur. For a scenario like this it's easier to just disable it then go through the trouble of setting up MSTP instance's.

If you're topology was setup to form a ring or a mesh (within a VLAN or VLAN's) then a broadcast storm would be possible and you would need to setup MSTP to prevent your network from going down.

But since most people use our switches for it's PoE capability to power radio's to connect to a particular link which is then just patched into a router. Typically the scenario is like yours where STP isn't really necessary if it's causing trouble.

Re: 2 Separate ptp links on 2 Switches

Posted: Fri May 22, 2020 11:21 am
by djboxny
ok, I dont have a router at my middle towers. i do have them at both ends of the link. thank you

Re: 2 Separate ptp links on 2 Switches

Posted: Fri May 22, 2020 7:57 pm
by Stephen
You're welcome, glad I could help.