Only able to route traffic thru a native vlan re:cisco router

Answered Question
Sep 22nd, 2010

Hello Expert,

I have one router with two ethernet interface.

I am working on allowing two different networks using one physical interface.

I set up a lab environment  to test the above.

I commence by sub interfacing the physical (fa 0/0) and created a two logical interface and defined as   Vlan 1 and Vlan 10. The addition physical interface is use a wan interface connects to host to simulating a remote site.

For my lan environment I connect a switch to the physical interface of the router .

On the switch I configured one port as  vlan 10 and all the other ports are members of vlan 1 by default  a trunk port is configured that allows  vlan 1 and 10 .

I connect two lap tops to the switch, laptop A connect to vlan1 and laptop B connect to vlan 10 .

Summary of set

Laps connected to switch , switch connect to router thru trunk port to lan side

The second Ethernet ( wan) is connect to host

Results of the lab test

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

From laptop A I can ping the remote host connected to the wan interface.

From laptop B I cannot ping the host connected to the wan interface.

I observe that laptop A is connect to port on switch defined as vlan1 with by default is native vlan.

If I defined vlan 10 as a native vlan , laptop B is able to ping the remote host.

I am confuse and unsure how to proceed.

Regards

I have this problem too.
0 votes
Correct Answer by Atif Awan about 6 years 2 months ago

Yes as Jon stated you need to make your switchport a trunk port so that it 'tags' frames with the required VLAN tag which the router is expecting (10 in your case). Once you make the switchport a trunk interface things should work.

Atif

Correct Answer by Jon Marshall about 6 years 2 months ago

rbglusers wrote:

hello Awan,

Attach is the info as per request.

I using the a cisco 3500 xl switch and the command 'show interface trunk'  is not returning any info i think this command is missing on this switch.

Any the other info is provide.

Regards

Is fa0/48 the uplink to the router ? ie.

interface FastEthernet0/48
switchport multi vlan 1-250
switchport mode multi

if so this is not a trunk. You need to change the config -

interface fa0/48

switchport mode trunk

Jon

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Overall Rating: 5 (2 ratings)
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Atif Awan Wed, 09/22/2010 - 10:43

If you share the relevant interface configurations of the switch and router that would help. Also share the output of the 'show interface trunk' from the switch. It is probably something minor but we will need to take a look at the configs.

Atif

jomo frank Wed, 09/22/2010 - 13:41

hello Awan,

Attach is the info as per request.

I using the a cisco 3500 xl switch and the command 'show interface trunk'  is not returning any info i think this command is missing on this switch.

Any the other info is provide.

Regards

Correct Answer
Jon Marshall Wed, 09/22/2010 - 13:48

rbglusers wrote:

hello Awan,

Attach is the info as per request.

I using the a cisco 3500 xl switch and the command 'show interface trunk'  is not returning any info i think this command is missing on this switch.

Any the other info is provide.

Regards

Is fa0/48 the uplink to the router ? ie.

interface FastEthernet0/48
switchport multi vlan 1-250
switchport mode multi

if so this is not a trunk. You need to change the config -

interface fa0/48

switchport mode trunk

Jon

Correct Answer
Atif Awan Wed, 09/22/2010 - 21:54

Yes as Jon stated you need to make your switchport a trunk port so that it 'tags' frames with the required VLAN tag which the router is expecting (10 in your case). Once you make the switchport a trunk interface things should work.

Atif

jomo frank Thu, 09/23/2010 - 07:00

hello Experts

,

I did the amendment as per post but did not get the connection via the two laptops

When I did the show run , I notice Vlan 1 is shutdown .

How do i restart this Vlan.(Vlan 1)

Regards

Jomo

Atif Awan Thu, 09/23/2010 - 07:38

rbglusers wrote:

hello Experts

,

I did the amendment as per post but did not get the connection via the two laptops

When I did the show run , I notice Vlan 1 is shutdown .

How do i restart this Vlan.(Vlan 1)

Regards

Jomo


You do not need to worry about the VLAN 1 SVI on the switch, just let it remain shutdown as you are only using the switch as Layer-2. It will be easier for someone to work with you for a couple of minutes to troubleshoot it, someone willing to spend sometime with Jomo? :-)

If you are unable to find someone who can walk you through it paste the output of the configs as well as the following commands:

From Switch:

show interface trunk

show vlan

Also explain the exact issue that you are facing. Are you able to ping the interface on the router from the laptop connected to the switch?

Atif

jomo frank Thu, 09/23/2010 - 08:10

hello Guys,

I found the error , my encapsulation on the trunk port was incorrect i corrected same and all is working.

thanks  thanks a million guys .

Regards

    

Jomo.

Jon Marshall Thu, 09/23/2010 - 08:07

In addtion can you make sure your default-gateways for the laptops are set to the subinterface addresses on the router.

Jon

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