Dot1Q trunk vs ISL trunk

From: David (david_knot@xxxxxxxxx)
Date: Mon Apr 29 2002 - 17:06:47 GMT-3


   
In the test lab, Ive 2 VLANs (Vlan 1 & 2) on catalyst
2912XL setup, with dot1Q trunks to a Cisco router. The
router has 2 subinterfaces corresponding to the vlans
(see config below). There is a token ring at the other
end of the router. The problem is that with dot1Q the
hosts on t ring cant talk to hosts on VLAN1 on the
cat. But if I replace the dot1 with ISL trunk then it
works fine.

Im being told that with dot1q I need an extra vlan to
make it work. Any ideas why? & what config changes are
needed.

Thanks a lot

version 12.0
!
hostname cat
!
interface FastEthernet0/1
 switchport mode trunk
 switchport trunk encapsulation dot1q
!
<deleted>
!
interface FastEthernet0/11
switchport mode trunk
 switchport trunk encapsulation dot1q
 spanning-tree portfast
!
interface FastEthernet0/12
 switchport mode trunk
 switchport trunk encapsulation dot1q
!
interface VLAN1
 ip address 192.168.1.1 255.255.255.0
!
line con 0
 transport input none
 stopbits 1
line vty 0 4
login
!
end

hostname R1
!
interface FastEthernet0/0
 no ip address
 duplex auto
 speed auto
!
interface FastEthernet0/0.1
 description Local LAN interface
 encapsulation dot1Q 1 native
 ip address 192.168.1.100 255.255.255.0
 no ip redirects
!
interface FastEthernet0/0.2
 encapsulation dot1Q 2
 ip address 192.168.2.100 255.255.255.0
 no ip redirects
!
interface tokenring0/0
 ip address 172.16.1.100 255.255.0.0
!
router ospf 1
 network 0.0.0.0 255.255.255.255 area 0
!
line con 0
 line aux 0
line vty 0 4
 login
!
end



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