When configuring "router on a stick" or Inter Vlan Routing between a router and a Ethernet switch is the Native VLAN required for dot1q trunking? Is the Native Vlan required for all trunk links between a router and switch. What's the purpose of creating a VLAN that's not tagging on trunk link?
Native VLAN is not required. IOS on router does not require a Native and Hybrid software on certain platforms allows you to configure all VLANs to be tagged. If you platform does not have the configuration option to tag all VLANs, you assign the Native VLAN to a bogus VLAN like 999, all other VLANs with traffic will be tagged.
Native VLAN is required. If you configure "router on a stick" using subinterfaces simply use "encapsulation dot1Q x native" on the subinterface belonging to the VLAN which is native on the switch end of the line.
The purpose of creating a VLAN that's not tagging on trunk link is enabling trunk negotiation and basic connectivity if the opposite trunk sites are not configured correctly.
IOS Versions prior to 12.1(3) don't allow the "native" parameter under the "encapsulation dot11 x" statement. So, under the Main interface ex. Fasteth0/1 you just configure an ip address. However, I'm having a problem because the router won't be able to see the switch on the other side that is configured as follows (on switch):
vtp domain test
int vlan 1
ip addr 10.12.1.2 255.255.255.128
switchport mode trunk
switchport trunk native vlan 1
switchport trunk allowed vlan all
int f 0/2
switchport access vlan 25
ip default-gateway 10.12.1.1
UNLESS you add the following statement:
on the router:
encapsulation dot1q 1
But, then, intervlan routing doesn't work....This is a catch 22 situation that needs to be resolved. Please help.
You need another statement in the switch config:
switchport trunk encapsulation dot1q
(default is ISL, I suppose you're using Cat3500 connected to the router via f0/1).
In you router config should be:
encapsulation dot1q 1 native
encapsulation dot1q 25
(again I suppose router connected to the switch via f0/1).
Your default gateway is strange: If IP address is 10.12.0.2 255.255.255.128 the default gateway should be 10.12.0.x where x is between 1 and 126. But you should still be able to route between PCs connected to switch ports in different VLANs 1 and 25.
You are right, mistake on my part, switch config has
ip default-gateway 10.12.1.1 with vlan1 on switch ip as 10.12.1.2 255.255.255.128. Gracias,
I tried your recommendations, router has following:
ip address 10.12.1.1 255.255.255.128
int f 0/1.1
encap dot1q 1
encap dot1q 25
ip address 10.12.2.1 255.255.255.128
ip helper-address 10.12.3.13
but then when w/s connects to 2950 switchport f0/2 , the w/s can only ping gateway, nothing else, not even dhcp server....
Should a bridge group be created for IEEE 802.1q?
Many thanks for your comments...
first move your
ip address 10.12.1.1 255.255.255.128
to int f 0/1.1
I "router on the stick" each subinterface has to have its own IP address within its VLAN!!
If it still doesn't work, the only remaining thing is the "native" for int f 0/1.1 .
Myabe you should try to move the "encap dot1q 1 native" command to int f0/1 or remove it at all.
BTW, using a 2950-48 switch running 12.1(6) where isl is not supported. So, switchport trunk encap dot1q x is defaulted to vlan1 and assumed on a trunk port.....appreciate your responses greatly.
Maybe you have a sample working config? Thanks!
I'm using Cat4000 as switch and Cat2948G-L3 as router on the stick.
If you want I can send you my config but I'm afraid it wouldn't help you much.
But I told you already what I think is necessary.
Thanks...really appreciate your effort....afraid your design is not similar based on software versions (running strictly Cisco Classic IOS on my devices)....Thanks for you help. Tried your recommendations, still no go.....muchas gracias amigo....
Regarding Router on a Stick/Inter VLAN Routing, is the following possible? The router is connected to a 6500 running CAT OS.
description Native VLAN
no ip address
description Mgmt VLAN
ip address 10.1.2.1/24
description User Segment
ip address 10.1.3.1/24
Since the physical interface is automatically the Native Vlan it will pass layer 2 instructions such as CDP..... According to some CCO docs it appears standard not to assign an IP address to physical interface. The management Vlan does not necessarily need to be on the Native VLAN.
According to previous posting VLAN999 is created to pass only Layer 2 info and does not have a subnet configured. Is this true?