[nsp] VLANs Trunk: dot1q <-> isl

Noriega, Alejandro ANoriega at prima.com.ar
Wed Mar 10 09:47:25 EST 2004


In effect the problem was de native VLAN. The other guy which manage the
SwitchB changed to VLAN 1 and now it works.

Thanks!!

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Stork, D.H.
(Duncan)
Sent: Wednesday, March 10, 2004 6:10 AM
To: 'cisco-nsp at puck.nether.net'
Subject: RE: [nsp] VLANs Trunk: dot1q <-> isl


Hi,

I think your problem is the native VLAN. You've configured it on the
ISL-trunk to 730, but you didn't set it on the dot1q-trunk. It's
required for dot1q on the switch to set the native vlan accordingly to
the one configured on the router.

Try this:

Switch A:
interface FastEthernet0/23
 duplex full
 speed 100
 switchport trunk encapsulation dot1q
 switchport trunk allowed vlan 1,730,1002-1005
 switchport mode trunk
 switchport trunk native vlan 730

Do the same on the incoming interface on switch B.

Best regards,

Duncan Stork

-----Oorspronkelijk bericht-----
Van: Noriega, Alejandro [mailto:ANoriega at prima.com.ar]
Verzonden: dinsdag 9 maart 2004 14:24
Aan: cisco-nsp at puck.nether.net
Onderwerp: [nsp] VLANs Trunk: dot1q <-> isl
Urgentie: Hoog


Hello fellows,
	I'm having a problem with a trunk configuration.
I have this topology:

	RouterA(fe1/0)---(fe0/22)SwitchA(fe0/23)---SwitchB---RouterB

RouterA:

interface FastEthernet1/0
 speed 100
 full-duplex
!
interface FastEthernet1/0.1
 encapsulation isl 730
 ip address 172.18.34.9 255.255.255.252

SwitchA:

interface FastEthernet0/22
 duplex full
 speed 100
 switchport trunk encapsulation isl
 switchport trunk allowed vlan 1,730,1002-1005
 switchport mode trunk
!
interface FastEthernet0/23
 duplex full
 speed 100
 switchport trunk encapsulation dot1q
 switchport trunk allowed vlan 1,730,1002-1005
 switchport mode trunk

If I changed the encapsulation in the router to dot1q and in the switch
trunk FE0/22 to dot1q I can to ping the RouterB (172.18.34.10). But I
need it to be ISL. Is Ok de configuration? Is there any command to
instruct the switch to translate the frames from ISL to DOT1q.

Thanks in advance.

Regards,
Alejandro.

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