Inter VLAN communication

Unanswered Question
Jul 1st, 2010

Hi,

1) I have created 4 VLANs as 10,20,30,99. (VLAN 99 is used for Management&Native)

2) used one VTP server & 3 VTP client modes. and each VLAN independandly communicating well.

3) And created 3 subinterfaces in a router for 3 VLANS ( encapsulation dot1Q 10, encapsulation dot1Q 20, encapsulation dot1Q 30)  

Here my quistion is that:-

1) Without any routing protocol will it happen Inter VLAN communication....? 

2) Is there need to create Subinterface for VLAN 99 (for Management&Native)

                                                                                         -Siyadh.

I have this problem too.
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John Blakley Thu, 07/01/2010 - 07:46

1) Without any routing protocol  will it happen Inter VLAN communication....? 

You would only be able to communicate with hosts in the same vlan, but intervlan communication would break.

Hosts in vlan 10 ---> 10 will work

Hosts in vlan 10 ---> 20 or 30 will not

2) Is there need to create Subinterface for VLAN 99  (for Management&Native)

No need to create one, but it takes the primary address on your interface:

int fa0/0 (vlan 99 = untagged)

ip address 192.168.0.1 255.255.255.0

int fa0/0.20

encaps dot1q 20

ip address 192.168.20.1 255.255.255.0

int fa0/0.30

encaps dot1q 30

It wouldn't hurt anything if you wanted to change your fa0/0 to encapsulate 99 if you wanted:

int fa0/0

encaps dot1q 99 native

HTH,

John

siyadh2020 Thu, 07/01/2010 - 08:01

Thank you John,

this is my routing table

C    172.10.0.0/16 is directly connected, FastEthernet0/0.1
C    172.20.0.0/16 is directly connected, FastEthernet0/0.2
C    172.30.0.0/16 is directly connected, FastEthernet0/0.3

And i did not configure any routing protocols.

But i am getting Inter VLAN communication(  vlan 10 ---> 10 or 20 or 30).

IP address of PC which is in VLAN 10

----------------------------------------------------------------------------------------------------        

          PC>ipconfig

          IP Address......................: 172.10.0.13
          Subnet Mask.....................: 255.255.0.0
          Default Gateway.................: 172.10.0.1

-----------------------------------------------------------------------------------------------------

Successfull ping from    172.10.0.13  (VLAN 10) to 172.20.0.13 (VLAN 20)
    

     PC>ping 172.20.0.13

     Pinging 172.20.0.13 with 32 bytes of data:

     Reply from 172.20.0.13: bytes=32 time=111ms TTL=127
     Reply from 172.20.0.13: bytes=32 time=140ms TTL=127

So i concluded without any routing protocol Inter VLAN communication will happen by subinterface.

                                                                                                                        - Siyadh.

John Blakley Thu, 07/01/2010 - 08:15

I completely misread your question. I thought you were asking if you weren't configuring routing for vlans. You're correct. You don't need a routing protocol (eigrp/bgp/ospf) in order to pass traffic. Sorry for my misreading....

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