VLAN help

Mar 20, 2006 3 Replies

Hi there,



I'm studying for my CCNA and am messing around with a few different VLAN scenarios.



Up until now, we have been taught to use different subnets for each vlan.



e.g. VLAN2 > 192.168.2.x VLAN3 > 192.168.3.x



However, I would like to see what happens when you have different VLAN's on the same subnet.



So, I've got two hosts;



Host A is on VLAN 2 and has an IP address 192.168.4.3/24 Host B is on VLAN 3 and has an IP address 192.168.4.20/24



I've configured the ports on the 2950 to enable static VLAN's for the two ports. Up until now, there is no problem...Host A can ping other hosts that have been assigned onto VLAN 2 and Host B can ping other hosts on VLAN 3. Neither can ping each other.



But, I'd like to configure inter-VLAN routing. Is this not possible because they are on the same subnet?



I've connected and configured a trunk link between the 2950 switch and a 2600 router, and set;


2600(config)# interface f0/1
2600(config-if)# no ip address
2600(config)# no shut
2600(config)# interface f0/1.2
2600(config-subif)# encapsulation dot1q 2
2600(config-subif)# ip address 192.168.4.1 255.255.255.0
2600(config-subif)# exit
2600(config)# interface f0/1.3
2600(config-subif)# encap dot1q 3
2600(config-subif)# ip address 192.168.4.19 255.255.255.0

However, Host A can ping both 192.168.4.1 and .4.10, whereas Host B can ping neither addresses.



Is it not possible to enable inter-vlan routing this way, or am I doing something wrong? I assume the problem is because you are assigning two subinterfaces on the same subnet on the router, but I thought that with the dot1q x command you were speciyfing that only VLAN x could communicate with it?



Would appreciate an explanation!



Thanks, Dilan



The best way I can put it. Lets say we have Main street in a city, an then someone names another street in the same city Main street. Who will ever know which Main street to go to? Peter.

Nice comparisation. Couldn't tell it better.

"Peter Fackrell" schreef >> Hi there,

Rule goes 1 subnet per Vlan.

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