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inter-vlan routing


I have a customer that has two vlans setup on their idf switches (vlan 10, 20).


on the core switch they all come in on multiple fiber trunks set for vlans (1, 10, 20)


ports 1/0/1-8 are access ports on vlan 10

ports 2/0/1-8 are acess ports on vlan 20


now they want to be able to have cross traffic from ports 1-8 vlan 10 to talk to devices on vlan 20, and ports 1-8 vlan 20 to talk to devices on vlan 10. 


can someone explain to me how to do this. (I'm pretty new at this but it makes no sense to me since it would be easier to get rid of the vlans since in doing this they seem to have no purpose).


i was told to setup vlan int on both vlans with ip addresses to use as gateways and the IP routing would take care of the rest, but I can't seem to make that work. 


help, the more I go into this the more confusing it is getting.

Thanks for any help.

7 Replies 7

Jon Marshall
VIP Community Legend VIP Community Legend
VIP Community Legend


Assuming your core switch is L3 capable then depending on the model you may need to enable routing ie. 


ip routing 


then - 


vlan 10 =
vlan 20 =


int vlan 10
ip address
no shut


int vlan 20
ip address
no shut


clients in vlan 10 have a default gateway of and clients in vlan 20 a gateway of 



Thanks john, i do have it programmed something like that (see updated post below), however it still doesn't work.
do I need to do anything else with IP routing? the core switch is a stacked 3850-24s and has layer 3 capability.

thanks for any info.

Joseph W. Doherty
Hall of Fame Master Hall of Fame Master
Hall of Fame Master
Whether you tried to go to using one VLAN, or to continue to use two, IP addressing on hosts in important.

Jon provides a great example of how your core switch might be configured and how the hosts PC need a gateway IP defined that corresponds to a SVI (switch virtual interface) on the core switch.


just to clarify;


my core switch has trunk ports. all trunk ports have vlan 1,10,20 on them.


also on my core switch I have ports gi1/0/1-8 as access ports on vlan 10

int vlan 10 ip address is


also on my core switch i have ports gi2/0/1-8 as access ports on vlan 20

int vlan 20 ip address is


ip routing has been enabled.


i set up access ports; 

gi3/0/1 access port on vlan 10

gi3/0/2 access port on vlan 20


my laptop is setup for testing as;


i can ping the gateway for vlan 20 (152.254) and one of my ip cameras on the same vlan (152.100)

i cannot ping the gateway for vlan 10 (151.254) or any of my cams on vlan 10.


what am I missing?


thanks again for your input.



post the full running configuration of the layer 3 switch...

Here it is;

Core-Switch-2.1.1#show run
Building configuration...

Current configuration : 13960 bytes
! Last configuration change at 17:54:54 UTC Fri Mar 6 2020 by admin
version 16.6
no service pad
service timestamps debug datetime msec
service timestamps log datetime msec
service unsupported-transceiver
no platform punt-keepalive disable-kernel-core
hostname Core-Switch-2.1.1
vrf definition Mgm