Default gateway

willbird · Nov 19, 2020

Apologies in advance if this is an ignorant question

. A few years back the Rockwell literature for how to setup say a powerflex 527 showed an example where the the IP was set to 10.202.10.05 for example, and they showed the default gateway being set the same as the drive, 10.202.10.05. Then a firmware revision changed things so that became an "illegal address" which left us to fix something with the 5 faceplate buttons

.

Some of our machines we ran into that because the existing drive was setup with gateway set to drive IP, we replaced the drive with new, and the newer firmware would not allow that setup.

Most of our stuff is setup 10.202.10.05 for drive, subnet 255.255.0.0 for subnet, and gateway then would be 10.202.0.1, if subnet is 255.255.255.0 then gateway is 10.202.10.1.

Ok so the question...are they actually USING the default gateway for anything on a typical machine network that might have say a PLC/PAC, three 527 drives, and an HMI ??

A friend is encouraging me to study for the CCNA exam so I have been digging into the network stuff a lot, which is good probably, it will help.

Bill

plvlce · Nov 19, 2020

Networks are not my strong point, but my understanding is that the default gateway is the node that serves as the access point to external networks. If your machine network has a router connecting it to a larger network then you'd enter its address.

If the drive only communicates with devices on its own network, I don't believe it will be actually used.

drbitboy · Nov 19, 2020

If the drives are only eithr connecting to, or connected to by, hosts on the same LAN*, then the gateway address is never used.

* "LAN" = "subnet" ~ "broadcast domain" = hosts where the [subnet mask] bit-wise ANDed with the drives' [IP address]

E.g. [netmask 255.255.255.0] AND [IP address 10.202.10.1] => [subnet 10.202.10.0].

I made an attempt to explain NAT (Network Address Translation) here, and Appendix I of that describes LANs/subnets/netmasks.

thingstodo · Nov 19, 2020

willbird said:
Apologies in advance if this is an ignorant question . A few years back the Rockwell literature for how to setup say a powerflex 527 showed an example where the the IP was set to 10.202.10.05 for example, and they showed the default gateway being set the same as the drive, 10.202.10.05. Then a firmware revision changed things so that became an "illegal address" which left us to fix something with the 5 faceplate buttons .

Some of our machines we ran into that because the existing drive was setup with gateway set to drive IP, we replaced the drive with new, and the newer firmware would not allow that setup.

Most of our stuff is setup 10.202.10.05 for drive, subnet 255.255.0.0 for subnet, and gateway then would be 10.202.0.1, if subnet is 255.255.255.0 then gateway is 10.202.10.1.

Ok so the question...are they actually USING the default gateway for anything on a typical machine network that might have say a PLC/PAC, three 527 drives, and an HMI ??

A friend is encouraging me to study for the CCNA exam so I have been digging into the network stuff a lot, which is good probably, it will help.

Bill

On the CCNA part ... this is a difficult exam that appears to accurately determine your proficiency with cisco switches, routers, configuration, etc. My brother, who at the time worked on switches about 20% of his day, every day .... took 3 tries to get a pass.

Others can chime in on this - I am not a CCNA myself. But from what I hear it is VERY practical. If you don't work on switches a lot you will have a hard time.

That said - good luck!

Dravik · Nov 19, 2020

The default gateway is the address a system will attempt to use as the default router to other networks outside the subnet a system is configured for.

For example -
IP: 10.10.10.10
MASK: 255.255.255.0 (or /24)
GW: 10.10.10.1 (The default gateway)
IP 10.10.10.10 will be able to 'talk to' all devices on 10.10.10.x w/ this subnet.

If 10.10.10.10 wants to talk to 10.10.20.20, It will ask 10.10.10.1 to route the requests there.
I

Dravik · Nov 19, 2020

Now, the default gateway is just that, the default.
You can also configure static routes to tell the above system that if it wants to talk to say -
10.10.30.30, then it should use a router located @ 10.10.10.2 instead of the 'default' GW @ 10.10.10.1

Dravik · Nov 19, 2020

willbird said:
*snip*
Ok so the question...are they actually USING the default gateway for anything on a typical machine network that might have say a PLC/PAC, three 527 drives, and an HMI ??

*snip*

Bill

And to answer this directly, if all the machine network devices are setup on the same 'network' w/ the same subnet, then no the default GW does jack all.

willbird · Nov 19, 2020

thingstodo said:
On the CCNA part ... this is a difficult exam that appears to accurately determine your proficiency with cisco switches, routers, configuration, etc. My brother, who at the time worked on switches about 20% of his day, every day .... took 3 tries to get a pass.

Others can chime in on this - I am not a CCNA myself. But from what I hear it is VERY practical. If you don't work on switches a lot you will have a hard time.

That said - good luck!

I have two Cisco switches here at home, and two more arrived today

. The first two were catalyst 3750, and the newest ones are WS-C3560-48PS-S. I'm into POE security cameras and the older cisco like that are a HUGE value at $30-$50 shipped

So I guess I have to work on them a lot in order to pass the test eh ?? I found a study guide and I'm digging into it. Also got the Cisco packet tracer software, what a neat tool

. Friend who suggested I do it passed with a 976/1000 score

. To say he picks things up quickly is an understatement. He used the practice exams to identify his weak spots like IPv6 and then worked on those. Worst case I study until my ears bleed and I pay $300 and fail, but still learned a lot, but I am good at studying for and taking tests so we shall see

.

I have worked with and do work with a lot of folks who are very proficient, their work borders on art really, but they suck at taking tests. And they have just settled down with "I suck at tests" when that too has tips and tricks that will help anybody score better with a fixed quantity of knowledge.

Bill

willbird · Nov 19, 2020

Dravik said:
And to answer this directly, if all the machine network devices are setup on the same 'network' w/ the same subnet, then no the default GW does jack all.

That makes perfect sense with them just a few years not even requiring you to enter one, and or suggesting you just duplicate the IP address

.

Bill

willbird · Nov 19, 2020

Thanks for the replies folks

. I have searched a lot of technical PLC questions over the last few years and ended up here for the answers. I call this the aquamarine forum when I see it on folks computers at work

.

Default gateway

willbird

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plvlce

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drbitboy

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thingstodo

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willbird

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willbird

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