Subnet -Vlan Communication

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Feb 5th, 2008
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Hi all,

is it possible for the Networks 1& 2 commute.

network1:,hosts to 6

broadcast subnet mask and

network2:,hosts to 14

broadcast subnet mask

will they come under different Vlans

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Jon Marshall Tue, 02/05/2008 - 03:54
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yes they are separate subnets and if you have them in separate vlans you will need a router or L3 switch to for the hosts to communciate with each other.



Hi Anand

You do not give very much information to work with, however if you have created 2 VLAN's on a switch and assigned 6 ports to each VLAN.

Then you have connected all the hosts with IP addresses in the range to to the ports assigned to one VLAN and all the hosts with IP addresses in the range to to the ports assigned to the second VLAN, then NO, these networks could not communicate without using a layer 3 device (either a router or if your switch has layer 3 functionality) as they are two totally different subnets (as defined by their respective subnet masks), even though the subnets are contiguous.

However if your switch has all the ports assigned to a single VLAN and you configure the hosts to use a /28 mask ( instead of the /29 mask ( then they would communicate, as all the hosts would think that they are members of the same /28 subnet.

The host will work out from the network/subnet mask assigned to it whether the host it is trying to communicate with is part of the same network/subnet or not. If it is, the packet will be sent towards that host. If it is not, then the packet will be sent towards the default router. If no default router is configured, the packets will be dropped and a "host not available" type message displayed to the user.

Please note that this second option is NOT a recommendation on how to get these two subnets to communicate. It's simply to illustrate that it could be possible. In a live environment the recommended method to get inter VLAN/Subnet communication is by the use of a layer 3 device.

Best Regards,


networking11 Thu, 02/07/2008 - 04:17
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In the attached diagram,the Routers in Daisy chain are to be connected to Aggregation Router and within the Daisy chain , the router have to be redundant .

Can u suggest me how to



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