> Why? As long as it can be a transparent router, why would it need to be
> a bridge?

Layer 2 CPE capability is a big deal, especially if you're doing unrouted 
multicast (see many TV/VoD over ethernet platforms for details).  But it's also 
nice for handing the customer a layer-2 service port like they're used to 
getting, if they want it that way.  The routing engine in CPE's is often simply 
not as capable as the bridging mechanism, so there's an end-user experience to 
consider.

It's also worth noting that this feature will probably become less important as 
IPv6 and DHCP6-PD becomes more widely deployed.  Until then, the extra routing 
in IPv4 starts to chew up some serious address space if you're rolling out 
thousands or more of the CPEs.  See most national ISP's CPE configuration if 
you think it's unusual to want to hand off services on a bridged interface- 
it's not, at all.

Nathan Eisenberg

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