VLAN trunk from switch to router

Unanswered Question
Jun 30th, 2006

We have a 2691 cisco router and a Linksys (cisco) 24 port switch.

Each E port is set with a different untagged VLAN ID grouped to G1 uplink port and is tagged

The G1 port then is trunked and is tagged to native VLan 1

One of the router ethernet ports is configued as

interface FastEthernet0/0

description $ETH-LAN$

no ip address

ip flow ingress

duplex auto

speed auto

no cdp enable

!

interface FastEthernet0/0.1

description $ETH-LAN$

encapsulation dot1Q 1 native

ip address 216.110.213.1 255.255.255.0

ip flow ingress

no snmp trap link-status

no cdp enable

!

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

Is this correct ?

Problem is all VLAN E ports on switch cannot get past the router.

Some E ports not with VLAN then default to VLAN 1 and they can function past the router.

The config of the switch was verified with Linksys as being correct which leaves a router config issue

So in short the switch would have 24 VLANs untagged going through trunk which is tagged ending up hitting router and then out WAN ports.

Thanks for any help for cisco and linksys have been no help solving why servers on switch with vlan cannot see past router

JR

I have this problem too.
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bosalaza Fri, 06/30/2006 - 09:36

Is this correct ?

A: The configuration above says that vlan 1 is native vlan, which means the router is expecting a "raw" packet to belong to vlan 1. "raw" packet menas it does not have any vlan id, I do not want to use "tag" coz "tag" might mean something else to Linksys. So, if it's "raw" as in if a PC transmit a packet, it will have no vlan id field.

Problem is all VLAN E ports on switch cannot get past the router.

Some E ports not with VLAN then default to VLAN 1 and they can function past the router.

A: If you mean, they can ping the 216.110.213.1 and beyond 216.110.213.0/24 then that would be expected.

The ports that belongs to other vlans will need a default gateway of their own, they cannot use the vlan 1 gateway because they are in different subnet. from the cofnig above, you only have sub-interface for vlan 1, do you have sub-interface for other vlans? If not, you need it.

The config of the switch was verified with Linksys as being correct which leaves a router config issue

So in short the switch would have 24 VLANs untagged going through trunk which is tagged ending up hitting router and then out WAN ports.

>> This goes back to above, native vlan on cisco router will be the only vlan the router will expect with no vlan id, otherwise, everything the router rx with no vlan id or dot1q encapsulation will be assumed that it belongs to vlan 1. do you have other sub-interfaces on the 2691 for the other 24 vlans?

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Posted June 30, 2006 at 9:17 AM
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