InterVlan Trunking between Catalyst 500 Express and Router 1841

[e.silva_2]

Hello,

I am currently attempting to configure 2 VLANs on a Router 1841 and allow them to communication with my Catalyst 500 Express switch. The Router Setup is simple

its 3 Sub-ints on the FE0/0 interface.

interface FastEthernet0/0

description $ETH-LAN$$ETH-SW-LAUNCH$$INTF-INFO-FE 0$

no ip address

duplex auto

speed auto

!

interface FastEthernet0/0.1

description *** ADMINISTERING VLAN ***

encapsulation dot1Q 1 native

ip address 10.19.1.1 255.255.255.0

!

interface FastEthernet0/0.2

description *** DATA VLAN ***

encapsulation dot1Q 2

ip address 10.19.2.1 255.255.255.0

!

interface FastEthernet0/0.3

description *** VOICE VLAN ***

encapsulation dot1Q 3

ip address 10.19.3.1 255.255.255.0

ip helper-address 10.19.2.2

FE 0/0 Port on the Router is connected to port 24 on my Catalyst. I set the Smartport on port 24 of the Catalyst to be Router for trunking purposes

I get a notification error on the Catalyst saying "Undersized frames detected from the connected device" (which is my ROUTER).

does anyone have a suggestion? Or Is it supported this scenario?

Thanks,

Eduardo

[gpulos]

can you post the config of your switch? what is the IOS version?

this could be a 'false' error as some cats/IOS have reported errors on dot1q frames of 61-64 bytes including the q-tag.

(affected ios are 12.1(19)ea1d, 12.1(20)ea1a, 12.1(22)ea1+ and 12.1(20)se1)

verify your MTU settings on the router and switch. also, try to set the router and switch to 100/full statically, not using auto.

[e.silva_2]

This is the config of the switch and the version 12.2(25)FY

I check the mtu setting and in the interface fasthernet 0/0 router is in 1500 and in the interface fastethernet 24 in the switch is in 1546, I tried to modify but is not allowed.

[rburden]

I had the same issue when I was working on CE500s and a WLC.

In the CE500 Device Manager, go to Configure->VLANs

Create your VLAN 2 and 3.

Then go back to smartports, click customize, and verify that VLAN-1 is default (native).

Sending information through a port on the CE500 that it is not expecting will set alerts in the log.

Hope this helps.

RB

[e.silva_2]

Hi RB,

I check in the smartports, customize and the default native vlan in the router port is the vlan 1.

Thanks