Quick-Series 29 : Mx – Bridge-Domain – Using Vlan-id None ? –

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Continuing on Bridge-Domains on Mx, I came across using vlan-id “none” and initially was surprised by this knob, I mean we create bridge-domain based on a Vlan and associate / segregate traffic based on Vlan-id.

Lets explore a use case or a remote scenario where this might come in handy.

Let us say you have customers with different vlan’s and you are about to be in merger and provide a common Layer-3 IP. Obviously, if you are in a situation where you have them on your sub-interfaces, you cannot have same vlan-id for two Sub-interfaces.

Let see what Vlan-id None can do here




Looking closely at the configuration, we see that vlan-id none has been used instead of being specific, but as you see the interfaces, they are clearly in vlans 101 and 102. So, how does this  work ?


There you go, there is a Pop in the inbound direction of the interface, a POP action popping out Vlan and the return traffic is now having PUSH action, hence traffic coming into bridge-domain will not care with what Dot1q tag the packet is coming-in.


Lets initiate a Ping and see if this works from two customer ends who are in different Vlans.


There you Go



Rakesh M

Quick-Series 28 – Vlan-Rewrite on Mx

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Vlan Rewrite on Mx is handy and can also be done fairly easily. Let see the scenario where it can come into help.


Problem – Service provider has Vlans, which are currently used by customers as well, so technically we cannot have a bridge domain combining our Internal Lan and Customer Lans (speaking purely from the post perspective)

Vlan Rewrite can be used to bypass this issue.

Initially customer tries to ping the SP, but there appears to be no reply from MX.


Now, lets configure Bridge domain for these two customers and have Routing-Interfaces associated to individual Bridge-Domains.


Configuring Vlan-Rewrite


Final verification is much simpler.




Rakesh M





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