layer 3 trunk interface

[suthomas1]

Hi,

A 3750 switch is connected to an upstream device. Two ports from 3750 connect to one each of the upstream device, which is in HA state.

Following is the configuration currently on the 3750:-

Int vlan 101

ip address 192.168.1.1 255.255.255.252

int gi0/21

switchport access vlan 101

switchport mode trunk

int gi0/22

switchport access vlan 101

switchport mode trunk

Multiple vlans will be traversing this link between the 3750 and the upstream devices.

The upstream device has a subinterface created with ip  192.168.1.2 tagged with vlan101.

The Ip's 192.168.1.1 & 1.2 are been used for routing the subnets located, from either of the devices.

In this case, is access vlan 101 command required on the physical interface on 3750?

Will we be able to establish ping and communication and use the ip's for routing if access vlan 101 is removed from both interface.

Thanks in advance!

[Reza Sharifi]

In this case, is access vlan 101 command required on the physical interface on 3750?

no, since the port is trunked, it is allowing all vlans.

You don't need

switchport access vlan 101

If you want to only allow vlan 101 in your trunk than have a look at this config:

interface Gi0/22

switchport trunk encapsulation dot1q

switchport trunk allowed vlan 101

switchport mode trunk

end

HTH

[suthomas1]

Thanks, so with only the following commands,on the interface;

switchport mode trunk

switchport trunk allowed vlan all

will the ip's 192.168.1.1 & 1.2 create an arp entry in each other device and be able to ping each other?

if yes, how will it work as the ip subnet is configured under vlan 100.

thanks.

[Reza Sharifi · Accepted solution]

If you want to allow all vlans, then just do this:

interface Gi0/22

switchport trunk encapsulation dot1q

switchport mode trunk

will the ip's 192.168.1.1 & 1.2 create an arp entry in each other device and be able to ping each other?

if yes, how will it work as the ip subnet is configured under vlan 100.

Yes, as long as you have an SVI on each switch, it will work fine. The source address will be the IP address on the SVI.

HTH