Help with Native Vlan

From: gladston@br.ibm.com
Date: Wed May 25 2005 - 14:25:32 GMT-3


If configuring native vlan other than 1, connectivity is lost.

Any idea?
version is 12.2(15)T5 for router 2600 and 12.1(20)EA1a for 3550

As it is an unexpected behavior I tested on another router and 3550. (but the IOS is the same).

R1----trunk----CAT1---vlan4--R7

Rack2R4#sh run int e 0/0.4
Building configuration...

Current configuration : 650 bytes
!
interface Ethernet0/0.4
 encapsulation dot1Q 4 native
 ip address 142.20.44.4 255.255.255.0
 ip access-group 150 in
 ip directed-broadcast
 ip multicast helper-map broadcast 229.1.1.1 110
 rate-limit input access-group 121 512000 64000 96000 conform-action continue exceed-action
drop
 rate-limit input access-group 122 64000 8000 12000 conform-action transmit exceed-action dr
op
 rate-limit input access-group 123 32000 4000 6000 conform-action transmit exceed-action dro
p
 no ip mroute-cache
 ip policy route-map Local-traffic
 ntp multicast 229.2.2.2
 ipv6 address 2001:1:1:4::4/64
 ipv6 address FEC0:2E3D:5B7C:4::4/64
 ipv6 nd suppress-ra
end

Rack2R4#
Rack2R4#sh vlan

Virtual LAN ID: 1 (IEEE 802.1Q Encapsulation)

   vLAN Trunk Interface: Ethernet0/0

   Protocols Configured: Address: Received: Transmitted:

Virtual LAN ID: 4 (IEEE 802.1Q Encapsulation)

   vLAN Trunk Interface: Ethernet0/0.4

 This is configured as native Vlan for the following interface(s) :
Ethernet0/0

   Protocols Configured: Address: Received: Transmitted:
           IP 142.20.44.4 37 90

Rack2R4#

Rack2CAT1#sh run int fa 0/4
Building configuration...

Current configuration : 203 bytes
!
interface FastEthernet0/4
 switchport trunk encapsulation dot1q
 switchport trunk native vlan 4
 switchport mode trunk
 switchport nonegotiate
 mls qos trust ip-precedence
 spanning-tree portfast
end

Rack2CAT1#sh int fa 0/4 sw
Name: Fa0/4
Switchport: Enabled
Administrative Mode: trunk
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: Off
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 4 (VLAN0004)
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk private VLANs: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none

Rack2R4(config-subif)#do pi 142.20.44.7

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 142.20.44.7, timeout is 2 seconds:
..

If native vlan is default, works fine:

Rack2R4(config-subif)# encapsulation dot1Q 4

Rack2CAT1(config-if)#sw tr na v 1

Rack2R4(config-subif)#do pi 142.20.44.7

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 142.20.44.7, timeout is 2 seconds:
!!!!!

This is the network:

R1----trunk----CAT1---vlan4--R7



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