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m.z
Beginner
Beginner

how to VLAN traffic from RSTP single instance to MST Instance 1

Hello,

 

I am using Cisco 3650 as L2/3 and another vendor Switch connected to it as Access Device with two parallel ports on different Vlans.

 

Cat 3650: Using MST. Having vlan1 in MST instance 0 and Vlans (2900, 2901) in MST instance 1. Two DHCP Pools 10.0.1.0/24 and 10.0.2.0/24 for both vlans.

Other Vendor: Using RSTP. It has a default Vlan 1 and two user Vlans (2900, 2901).

 

Requirement: I want my Other Vendor Vlans (2900, 2901) to talk to Cat 3650 but only with its Instance 1 which is having Vlans 2900 and 2901. But other vendor switch is creating a loop and blocking its port because RSTP puts all Vlans in single instance and when it sends traffic to 3650 it communicates only with MST instance 0 which in turn makes a loop. It doesn't communicate with to MST 1 which is having Vlans 2900 and 2901.

 

* Picture attached.

 

Question is: What/How should I configure my Switches so both the VLANs communicates with corresponding VLANs on other side (RSTP <---> MST instance 1)?

 

 
1 ACCEPTED SOLUTION

Accepted Solutions
pieterh
VIP Collaborator

on both Cisco and foreign switch you need to limit the "allowed vlan" to 2900, 2901 on the trunk port connecting both switches

for Cisco:

- interface Gixx/yy

-   switchport mode trunk

-   switchport allowed vlan 2900, 2901
this way no MST0 vlan reaches the foreign switch and vica versa.
if the foreign switch NEEDS to communicate over vlan 1 then it's more complicated
if the same config as for Cisco is valid on your foreign switch, then you're done.

 

View solution in original post

1 REPLY 1
pieterh
VIP Collaborator

on both Cisco and foreign switch you need to limit the "allowed vlan" to 2900, 2901 on the trunk port connecting both switches

for Cisco:

- interface Gixx/yy

-   switchport mode trunk

-   switchport allowed vlan 2900, 2901
this way no MST0 vlan reaches the foreign switch and vica versa.
if the foreign switch NEEDS to communicate over vlan 1 then it's more complicated
if the same config as for Cisco is valid on your foreign switch, then you're done.

 

View solution in original post