Having troubles with Q-in-Q on CRS305

RouterOS General
1

Hi,

Today I stumbled on an issue which I am not sure how to resolve and if it can be resolved at all.

Let’s say I have two CRS305 switches which are connected to sfp-plus2 to each other and are sending tagged frames with VLAN 200.
I also have two CPEs that are each connected to sfp-plus1 on each one of the switches.
Those two CPEs must communicate with each other over ANY vlan (e.g. each CPE has configured VLAN 120 and VLAN 150), which means the switches should be able to capture tagged frames on input (C-tag), transport them over VLAN 200 (S-tag), and drop the s-tag on output.

This is easily done with any RB router. you just create a VLAN interface on your WAN interface (in this case towards the other switch) and bridge that VLAN interface with the physical LAN interface (in this case towards the CPE).

However, that does not seem to be the case with CRS305.
I followed the wiki (https://wiki.mikrotik.com/wiki/Manual:Interface/Bridge#VLAN_Tunneling_.28Q-in-Q.29) and it does not work.

Any ideas as to why? Is it a config problem or is it simply not possible on the CRS305 switch?

2

Post anonomized output from /export file=yourfilename between code brackets so we can see config and assist where possible

3

Sorry for my late response, I was away for a few days and didn’t have access to the device:

/interface bridge
add ether-type=0x88a8 name=BR-Service vlan-filtering=yes
/interface bridge port
add bridge=BR-Service interface=sfp-sfpplus2 pvid=1535
add bridge=BR-Service interface=sfp-sfpplus1
/interface bridge vlan
add bridge=BR-Service tagged=sfp-sfpplus1 untagged=sfp-sfpplus2 vlan-ids=1535
/interface vlan
add interface=BR-Service name=MGMT vlan-id=1535
/ip address
add address=172.31.255.2/30 interface=MGMT network=172.31.255.0

4

You are not showing full config, so it makes it difficult to assist.

All I can assume at this stage is that possibly you don’t have “use service tag” configured on the vlan interface

5

That is the whole configuration on the Mikrotik switches.

The CPEs have a simple configuration of a subinterface with an encapsulation and an IP:
E.G.
CPE 1
int Gi0/1.150
encapsulation dot1Q 150
ip address 192.168.69.1/30

CPE 2
int Gi0/1.150
encapsulation dot1Q 150
ip address 192.168.69.2/30

Last week I tried with ether type 0x8100 and tag-stack as well.

After several tests with another device (RB760iGS) I found the issue on a middle device in the network which for some reason was unable to carry more than one tag.
After eliminating that issue, I switched to 0x8100 with tag-stacking and had ping between the CPEs.