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Cisco 4K ISR Serial to Ethernet Bridge

Good morning,

We are upgrading our old environment (C2800) to the new Cisco 4000 series routers.


We use one router as an bridge from multiple serial interfaces to an Ethernet interface, see attached file. 


Now we are encountering an problem that the bridge-group command isn't available on the 4K platform anymore. 
Also EVC's are only supported on Ethernet interfaces, not on serial. 


After some hours of digging the internet, I cannot really find a way to accomplish this. Or is the only solution to stick with the older platforms?




Georg Pauwen
VIP Expert



to partially answer your question, bridge virtual interfaces have morphed into bridge domain interfaces in XE on the ISR4K. Here is an example:


interface Gig0/0/1
service instance 10 ethernet
encapsulation dot1q 10
rewrite ingress tag pop 1 symmetric
bridge-domain 10

interface BDI10
ip address X.X.X.X
no shut


Understanding Bridge Virtual Interface (BVI) and Bridge Domain Interface (BDI)

Hi George,

Thanks for your reply.
Unfortunately, the bridge-domain (the whole service instance) isn't available on serial interfaces if I recall (I'll test it).




unfortunately the serial interfaces don't seem to support BDIs...{:


Check the thread below for maybe an allternative...



Found the thread earlier, but from the thread:

"In other words, there is the only one interface in bridge group (int serial 0/0/0:0) and it allows ISR to cooperate with PPP half-bridge device."

In our case there are 8 serial links that need to be bridged to 1 Ethernet interface, so I don't think that is going to work.





annoying indeed...I guess support for serial interfaces is waning.


I remember that you can group serial interfaces in a ppp multilink. I cannot test this so it is just speculation, but a PPP multilink interface would just be one interface, and possibly it works that way ?

Hi Georg,


Thanks, I'll look into that!

But if I read this article:

"Multilink PPP allows packets to be fragmented and the fragments to be sent at the same time over multiple point-to-point links to the same remote address."


Problem here is, all the 8 Serial interfaces are going to different endpoints :(.