Noo question... Subnetmasks and gateways

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Paully's5.0

Limp Gawd
Joined
Jun 18, 2002
Messages
398
Ok I have a single network, but want to setup multiple subnets and for management purposes I want my computer to access all 4 subnets. I have multiple switches and am confused on the gateway configuration or if what I want to do is possible.

Subnet 1:
192.168.1.x
255.255.255.0

Subnet 2:
192.168.2.x
255.255.255.0

Subnet 3:
192.168.3.x
255.255.255.0

Subnet4:
192.168.4.x
255.255.255.0

I wish to keep devices on each subnet isolated, so devices on subnet 1 cannot communicate with devices on subnet 2, 3, or 4. Same for the devices on the other subnets.

Now, from a management perspective I would like to set my computer IP address to something like:
192.168.0.10
255.255.0.0

So I could jump subnets w/o chaning my IP address. But I know I need a gateway to do this, but I do not have a router. I have managed switches (layer 2) in each network so can I configure one of these switches as the gateway to allow me access to the other subnets?

If so, would the switch need to be setup:
192.168.0.1
255.255.0.0

Then my computer IP address end up bing:
192.168.0.10
255.255.0.0
192.168.0.1

It's not critical, just looking for a way to limit the hassle of changing my IP address on my laptop. There is no r
 
Just curious, if you don't have a router, then you are not assigning DHCP addresses. So all of your devices are being set statically?

Paully's5.0 said:
Now, from a management perspective I would like to set my computer IP address to something like:
192.168.0.10
255.255.0.0
Click to expand...

Your subnet mask would be 255.255.192.0
 
you can't really segment your networks this way... they may be segmented logically, but not physically...

also your other networks don't have a subnet mask that would allow them to communicate back with your box at 0.10....

typically what you do is set up these separate subnets physically (separate the networks, either by different switches/routers/vlans on the same switch) and route between them with a router, and use firewalls to prevent the traffic you do not want from passing...

to do what you're doing, i would suggest just adding an ip address for each network up on your single nic... most OS support virtual IPs like this...
 
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Thanks for the responses, this is for an automation network (device-level control) where static IP addresses are the norm and isolation of the devices is ideal. Due to client restrictions things like VLANs, Layer 3 switches and routers are not allowed. So for setting up the devices just wanted to see if there was a way I could access all the networks w/o having to change my IP addresses. I didn't think there would be but I don't get into gateways and routing all that often.

Thanks alot!
 
Paully's5.0 said:
Thanks for the responses, this is for an automation network (device-level control) where static IP addresses are the norm and isolation of the devices is ideal. Due to client restrictions things like VLANs, Layer 3 switches and routers are not allowed. So for setting up the devices just wanted to see if there was a way I could access all the networks w/o having to change my IP addresses. I didn't think there would be but I don't get into gateways and routing all that often.

Thanks alot!
Click to expand...

yep, just go in windows in the ipv4 settings of your NIC, and hit the advanced button on the bottom...

add an address from each network and you should be good to go....
 
You can't have a computer on a /16 that encompasses all your /24s talk to all of them. What copper mentioned won't work.

The computer will send to each device fine but the devices won't be able to reply because the original computer is outside of their network.

Either add multiple IPs on the PC or use a L3 switch or Router on a stick setup.
 
/usr/home said:
You can't have a computer on a /16 that encompasses all your /24s talk to all of them. What copper mentioned won't work.

The computer will send to each device fine but the devices won't be able to reply because the original computer is outside of their network.

Either add multiple IPs on the PC or use a L3 switch or Router on a stick setup.
Click to expand...

wat? thanks for saying the same thing i did, then saying what i said won't work, lol

re-read the thread /usr/home
 
goodcooper said:
wat? thanks for saying the same thing i did, then saying what i said won't work, lol

re-read the thread /usr/home
Click to expand...

No, I said making the subnet mask larger on the PC won't magically allow it to talk to all subnets within it.

Ah I see where you are confused. There was a guy named copper (not cooper) that posted just making the subnet mask larger would work.

TLDR - we are saying the same thing.
 
/usr/home said:
No, I said making the subnet mask larger on the PC won't magically allow it to talk to all subnets within it.

Ah I see where you are confused. There was a guy named copper (not cooper) that posted just making the subnet mask larger would work.

TLDR - we are saying the same thing.
Click to expand...

wow i'm so sorry... and i'm used to people misreading my name as copper...

my apologies /usr/home

and in most cases yes, we do say the same thing

high five o/
 
theres a lot of misinformation here, so heres the short and correct answer,

no, you cant go between subnets without a layer 3 device to do the routing, and an interface in each subnet. your pc will use the subnet mask and see that the ip address is outside the subnet and without a default gateway it just wont work.

The end.
 
WeenieWorld said:
theres a lot of misinformation here, so heres the short and correct answer,

no, you cant go between subnets without a layer 3 device to do the routing, and an interface in each subnet. your pc will use the subnet mask and see that the ip address is outside the subnet and without a default gateway it just wont work.

The end.
Click to expand...

Soooooo... you just repeated what everyone said. Gotcha.
 
Actually WeenieWorld used incorrect grammar making his statement wrong anyway (or that was what he meant and is wrong regardless) lol

"you cant go between subnets without a layer 3 device to do the routing, and an interface in each subnet"

Should be OR an interface in each subnet haha

AND you don't need a default gateway either if you use static routes lol
 
wut
this thread is cunfusing
seems like you should be able to add the ip's from each subnet to your NIC and be able to access the other subnets. Why wouldn't that work such as this from my home


 
You are correct unless you're dealing with VLANs.

If you're only on one VLAN and there's no tagging going on then adding an IP/Subnet to an adapter will create a route in your computers routing table to that subnet out of that interface and allow it to respond to traffic destined for its IP address in that subnet.

I personally would not have more than one default gateway unless you had a real reason for doing that but it'll work in most cases.
 
MysticRyuujin said:
You are correct unless you're dealing with VLANs.

If you're only on one VLAN and there's no tagging going on then adding an IP/Subnet to an adapter will create a route in your computers routing table to that subnet out of that interface and allow it to respond to traffic destined for its IP address in that subnet.

I personally would not have more than one default gateway unless you had a real reason for doing that but it'll work in most cases.
Click to expand...

The 2nd set is my kids network and i use it to Manage their router/ap I found that i couldn't access the router unless i added the gateway. Ive never done it like that before but this worked. what negative implications could te 2nd gateway cause? hasnt yet but im interested.
 
Depends on the OS routing table but if they are load balanced then stateful traffic could be broken up between the two gateways and result in stateful firewalls dropping traffic that doesn't make sense to them.

For example if you had two routers going out two different lines with two different firewalls protecting them. Your computer could load balance between the two routers but your firewalls would probably freak out because they would only see half a conversation. Or perhaps they go to two different ISPs or just have different external IP addresses. Can confuse some statefull apps as it thinks it's having a conversation with two IP addresses.

It can also lead to jittery traffic, meaning some packets arrive faster than others or not in a consistent manner. That's bad for streaming stuff like VoIP.
 
MysticRyuujin said:
Actually WeenieWorld used incorrect grammar making his statement wrong anyway (or that was what he meant and is wrong regardless) lol

"you cant go between subnets without a layer 3 device to do the routing, and an interface in each subnet"

Should be OR an interface in each subnet haha

AND you don't need a default gateway either if you use static routes lol
Click to expand...

so hes supposed to enter a static route for every block on every host in every subnet?

nice solution mr ccnp... lol.
 
Oh ouch. You got me. I'm a fake. I have no idea what I'm doing.

I never said it was a practical solution, did I? In fact, I'm pretty sure that anyone besides you would see the "lol" after that sentence and know it was a joke.
 
Windows in general handles multiple default gateways...thanks TCM2..lol poorly..i'm sure you got the nice message when you added the second gateway stating that you will have multiple gateways blah blah blah..

If you do a route print you can see how your OS is handling traffic. Of course, since you have multiple gateways, you may have to manually set the metric for each.

I hate hate hate multiple gateways with Windows.
 
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Ahh...yes...multiple gateways..thank you...must get some sleep.
 
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