native vlan on switch port

[suthomas1]

Hello,

We are configuring a router and switch for a location with following configuration outline.

1. Routers gi0/0/0 connects to fa0/48 on switch
2. Router will be as dot1q with multiple segments tied from gi0/0/0
3. Switch fa0/48 will be a trunk allowing all vlans , switch itself will have about 7 layer2 vlans
4. Management for both router and switch will be on vlan 100(192.168.100.0/28)
router - 192.168.100.11 & switch - 192.168.100.12

interface GigabitEthernet0/0/1.100 (on router)
description device management
encapsulation dot1Q 100
ip address 192.168.100.11 255.255.255.240

interface fa0/48 (on switch)
description device management
switchport trunk encapsulation dot1q
switchport mode trunk
switchport trunk native vlan 8

int vlan 100 (on switch )
ip address 192.168.100.12 255.255.255.240

5. The router will do all routing upstream and the switch will only have layer 2 functionality

In this case, will the fa0/48 config on switch work well from a native vlan perspective?
Do we need to specify explicity vlan 8 as native on switch port fa0/48? What happens if we
do not specify (which will then default native to 1) ?

Will this affect connectivity in any aspect for the rest of vlans on that location.

please help with inputs.

[paul driver · Accepted solution]

Hello

---

@suthomas1 wrote:

In this case, will the fa0/48 config on switch work well from a native vlan perspective?

---

By default the native vlan will be on the physical interface of the router, Now as the router is performing the inter-vlan routing and you have also specified native vlan 8 on the switch trunk then on the router you could also make its related sub-interface native with/without ip addressing.

interface GigabitEthernet0/0/1.8 (on router)
description device management
encapsulation dot1Q 8 native
no ip address

---

Do we need to specify explicity vlan 8 as native on switch port fa0/48? What happens if we

do not specify (which will then default native to 1) ?

Will this affect connectivity in any aspect for the rest of vlans on that location.

---

No you don't have to specify any native vlan and the default will be vlan 1 on the physical interface of the router and on the trunk of the switch and all should work accordingly

[Richard Burts]

The original poster has not told us much about vlan 8. We are told that the switch is performing layer 2 forwarding with no layer 3 processing other than the IP for the management interface. If the intent is that there will be hosts connected in vlan 8 that need to access resources outside of vlan 8 then the router sub interface for vlan 8 needs to have an IP address. If vlan 8 does not have hosts that need to be routed then the suggestion of the router sub interface for vlan 8 with no ip address would be fine.

HTH

Rick