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showing machines on different vlans

Posted on 2013-12-09
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Last Modified: 2013-12-30
ok, we can access machines by ping and running apps over 2x different vlans.
Problem i have is that i am unable to see machines in the other vlan in network places or in dameware.
i can see them by unc name and ip fine so the routing is working.

i added dns entries for IPs for the vlan on our dns servers.

Ideas why the machines can be seen?

thanks
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Question by:CHI-LTD
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by:CHI-LTD
ID: 39706056
to add, the server on vlan20 is on a 172.16.0.0 with static of 172.16.10.30.
GW (switch) of 172.16.4.5
DNS servers 172.19.10.17 and .18 (on vlan1)
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by:Daniel Helgenberger
Daniel Helgenberger earned 285 total points
ID: 39706097
In Windows, you 'see' network places because of a broadcast the machine sends witch other clients respond to.
I think for starters, there are two posible things to check:
1. Is network discovery switched on in  Windows:
http://windows.microsoft.com/en-us/windows7/enable-or-disable-network-discovery

2. Does your switch permit broadcasts?

HTH,
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by:Red-King
Red-King earned 143 total points
ID: 39706160
As helge000 said, Windows Network Discovery uses broadcasts to see other devices on the network.
When you are using VLANs your traffic needs to go to a router to get a route to the other VLAN.
By default, most routers disable the routing of broadcast traffic. Normally a VLAN will coincide with a subnet i.e. one subnet to one VLAN. Subnets break up broadcast domains.

If you want to allow broadcast traffic to route between VLANs you need to specifically enable that on your router.
If you do enable broadcast routing you are enabling it for all broadcast traffic so use this with care as you'll increase the traffic across your entire network.
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by:Daniel Helgenberger
Daniel Helgenberger earned 285 total points
ID: 39706228
Hello,

Red-King, thanks, I overlooked this (for some reason I seem to have difficulties reading the headlines ;) - you want to 'see' the machines in different VLANs.

This is, however:
a) not desirable at all (see above) and
b) I think not even possible with Windows.  At least LLTD does only work in its own segment:
http://en.wikipedia.org/wiki/Link_Layer_Topology_Discovery

Please keep in mind routing broadcasts is something which should never been done. The permutations are endless; please see broadcast storming:
http://en.wikipedia.org/wiki/Broadcast_storm

Think of broadcasts as a thing of the past for troubles and overheads it can cause. IPv6 for instance depreciated broadcasts in favor for multicasts - which are much more efficient.
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by:CHI-LTD
ID: 39706482
so recommended leave as is?
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by:
Daniel Helgenberger earned 285 total points
ID: 39706744
I would say leave it. I consider it only as a minor nuisance if you are not able to see the other computers in the Network Tab. Other more imported things work well.
Normally I have this feature turned off anyway as it poses a security risk.

You can however use directed broadcasts for things like WOL. If you're interested, read this Cisco KB - article, though I do think it helps litte with your current problem: http://www.cisco.com/en/US/products/hw/switches/ps5023/products_configuration_example09186a008084b55c.shtml

Please keep in mind you potentially enable smurf and fraggle attacks.
http://en.wikipedia.org/wiki/Smurf_attack
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by:Craig Beck
ID: 39707037
If you want to discover hosts on other VLANs you could try using WINS.
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Author Comment

by:CHI-LTD
ID: 39707997
could try, as in it works or are you guessing?
we have it installed with push/pull to another wins server..
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by:Red-King
Red-King earned 143 total points
ID: 39708021
Something else you could try, which may or may not work, would be to configure a Trunk port from the switch to your PC.
If the NIC on your PC has the feature available to specify VLANs (usually in device properties, under the advanced tab) you may be able to specify multiple VLANs for your NIC.
You'd then add an alias IP for each VLAN/Subnet to the NIC and try running the broadcast again.

This might not work as your broadcast traffic out may get tagged with just one VLAN ID meaning it would be dropped from the other VLANs.

That's complete speculation on my part. It might be fun to try it if you enjoy that kinda thing but Helge000 has you covered with the definitive information.
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by:Daniel Helgenberger
Daniel Helgenberger earned 285 total points
ID: 39708028
Of course, Multi-Homing the PCs should work. You would see all the network places. Just put them in both VLANs; eg. tag the other VLAN accordingly. Today any NIC is VLAN capable with the correct drivers.

I did point this not out because I think your VLAN setup would be rather pointless if you do that; but may be a valid solution for you.
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by:Craig Beck
Craig Beck earned 72 total points
ID: 39709835
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by:CHI-LTD
ID: 39746104
wins enabled and running.  left itr as is...
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