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Networking issue

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Last Modified: 2015-01-21
We have a vlan 11 with a DHCP range of 10.11.20.1 - 10.11.254.254 default gateway of 10.11.0.1.

all clients that have an IP address of 10.11.0.x and work fine. All clients that get an IP of 10.11.1.x cannot ping anything (server, gateway, printers, not internet) or be pinged. All client on vlan11 have the same default gateway.

We have a Cisco firewall and cannot find any settings that could be causing this issue. Of course I could be overlooking something.

Not sure if the core switch would do anything. DHCP and DNS are controlled by a windows 2008 DC.

Any ideas?
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Paul MacDonaldDirector, Information Systems
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Commented:
What subnet mask are you using?

Author

Commented:
255.255.248.0

Author

Commented:
I think you are on to something. Should we use 255.255.0.0? If so, it is greyed out in the DHCP settings on our windows dc
Paul MacDonaldDirector, Information Systems
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Commented:
You can't change it, I believe, once you've established the DHCP Scope.  You have to re-create it.

Author

Commented:
that's not going to be fun. Would we use 255.255.0.0?
Paul MacDonaldDirector, Information Systems
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Commented:
"Would we use 255.255.0.0?"
I can't answer that question for you.  It seems like it would be valid for you, but whether or not it's the best choice...

If creating a new scope is too much trouble, you can create a superscope instead and proceed that way.

Author

Commented:
i just looked at the settings we are using on a IP address calc.

The subnet mask that we are using should be fine. It has a range of 10.11.0.1 - 10.11.7.254

Author

Commented:
ok I found the issue. It was our settings in our core switch. VLAN11 is using subnet mask 255.255.255.0. My new question is if I change the vlan 11 subnet mask to 255.255.248.0 on the core switch would it cause any issues with the devices that are already connected? Will it change the settings in all my other switches?
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Paul MacDonaldDirector, Information Systems
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This one is on us!
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