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Unread September 15th, 2019, 10:19 PM   #1
Poykim
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Etap

HI, can someone explain to me what is the purpose, use and function
of ETAP by AB. thank you
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Unread September 16th, 2019, 08:39 AM   #2
ivo.maenen
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https://www.google.com/search?client...d&q=ETAP+by+AB
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Unread September 16th, 2019, 12:10 PM   #3
dmroeder
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AB has the concept of a Device Level Ring (DLR), where you can connect Ethernet I/P devices in a ring topology. In order for this to work, each device needs Ethernet ports that are designed to be connected in this way. Not all devices have 2 ports, so they make an ETAP for this case. The ETAP has the 2 ports, which allow it to be connected in the ring, plus the 3rd port for the device.
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Unread September 17th, 2019, 03:19 AM   #4
Poykim
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Why they dont use switch instead of ETAP
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Unread September 17th, 2019, 04:15 AM   #5
cardosocea
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Quote:
Originally Posted by Poykim View Post
Why they dont use switch instead of ETAP
And miss out on the opportunity to overcharge their customers??
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Unread September 17th, 2019, 08:43 AM   #6
iggy
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Quote:
Originally Posted by cardosocea View Post
And miss out on the opportunity to overcharge their customers??
I would disagree about price, they come in very handy for adding a device that does not have DLR.
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Unread September 17th, 2019, 08:54 AM   #7
TheWaterboy
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A switch would consider the ring topology of DLR a loop. You could configure a managed switch with STP to allow for that or you could mirror a port, either of which then blocks the ring topology from working.

Even if that would work your managed switch now is as expensive as an ETAP but introduces more complexity and management into the network.

ETAP is a single purpose promiscuous tap so it has its place in the universe for older gear that needs to have redundant network connection.
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Unread September 17th, 2019, 10:07 AM   #8
harryting
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ETAP is not just another 3-port switch!!!

DLR is using a completely different ring protocol than the standard STP or RSTP.

The problem with standard ring protocol is that they are too slow for industrial applications. It's not just Allen Bradley either. If you buy a N-Tron or Hirchmaan, they also have their own proprietary ring protocol. Therefore you have to match the type of switches carefully.

If you opt to use standard Cisco switch and do redundant ring or redundant star configuration. You have to carefully plan out the routing scheme. Often this will involve using ether-channels. You can't just plug multiple cable/fiber together and expect things will work out. The problem is, often they do "work" until a power bump and all the switches started to broadcast at the same time. Yes, I seen that scenario more than once.
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Unread September 17th, 2019, 06:57 PM   #9
JaxGTO
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Be careful using these. I was just told by AB that is giving the blessing on a project I have coming up that the ETaps are causing problems when you use VLans and a 3 layer switch. So if you have those in your system, watch out.
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Unread September 18th, 2019, 09:23 AM   #10
harryting
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Are you talking about KB 631448?

Basically it says ETAP doesn't support trunking. However, this doesn't mean the DLR can't be part of a VLAN, just means ETAP can't combine bunch of VLAN together.
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