Intervlan routing - ping from one vlan to another not working.

[nick.szilagyi]

Hi all,

I have a question/issue regarding pinging between vlans.

I've configured a 3750 with a 3 vlans (1,20,100) to trunk to my 3825.

All vlans are allowed across the trunk both sides and sub interfaces are configured on the 3825.

I've configured one of my access ports to vlan 20, connected my laptop and successfully leased an ip address from the dhcp scope I created for vlan 20.

From my client, with an IP address of 192.168.20.xxx, I am  able to ping the SVI gateway and the sub interface of the router, 192.168.20.254 and 192.168.20.1. No problems here.

From the same client, I am not able to ping the G0/1 router interface 192.168.1.1 but I can ping the switch SVI of 192.168.1.254.

Show ip route shows the appropriate routes back via the directly connected interface/suninterface for vlan 1 and vlan 20 subnets.

Can someone kindly explain why I am unable to ping 192.168.1.1? (I can ping 192.168.1.1 directly from the switch).

Is this something do with the fact that the 192.168.1.1 is not within an encapsulated dot1q interface?

//switch//

interface GigabitEthernet1/0/1 //router uplink
switchport trunk encapsulation dot1q
switchport mode trunk

interface Vlan1
ip address 192.168.1.254 255.255.255.0
!
interface Vlan20
ip address 192.168.20.254 255.255.255.0
!
interface Vlan100
no ip address
shutdown

//router//
interface GigabitEthernet0/1  //switch uplink
ip address 192.168.1.1 255.255.255.0
duplex auto
speed auto
media-type rj45
!
interface GigabitEthernet0/1.20
encapsulation dot1Q 20
ip address 192.168.20.1 255.255.255.0
!
interface GigabitEthernet0/1.100
encapsulation dot1Q 100
ip address 192.168.100.1 255.255.255.0
!

Many thanks,

Nick.

[Mark Malone · Accepted solution]

Hey you shouldn't have an ip here it should be blank and another dot1q created for it , you told the int act as trunk but then gave it an ip , create a g0/1.10 with that ip address and assign vlan to it

//router// interface GigabitEthernet0/1 //switch uplink ip address 192.168.1.1 255.255.255.0 duplex auto speed auto media-type rj45 !

[Mark Malone]

take a look at this , example of router and stick setup which is what you are trying to achieve above http://www.firewall.cx/cisco-technical-knowledgebase/cisco-routers/336-cisco-router-8021q-router-stick.html

[nick.szilagyi]

Hi Mark,

Thank you, I suspected it was due to this but unable to fully understand why?

From the switch I can still ping 192.168.1.1, but unable from the client. Can you help to explain?

[Mark Malone]

what do you have currently in configuration after making the changes , as well you only need 1 vlan interface on switch side for MGMT reachability purposes and you should use a vlan which is not production traffic if the switch is layer 2.

You prob need to shut down the vlan 1 interface on switch as you already have a gateway interface 192.168.1.1 same subnet set on router interface so when client pings he probably hit the vlan int on the switch