The port 1/1/1 is configured in qinq mode, enabling it to process frames with either a single 802.1Q tag (S-tag) or two tags (an outer S-tag and an inner C-tag). The SAP 1/1/1:100. is configured within VPLS 2. The acts as a wildcard for the inner C-tag. Therefore, any frame arriving on port 1/1/1 with an outer (top) tag of 100, regardless of the inner tag's value, will be matched to this SAP and processed by VPLS 2. Consequently, the source MAC address of such a frame will be learned in the forwarding database (FDB) of VPLS 2.

A. While it is true that untagged frames will be dropped because no SAP is configured to match them, this describes a default behavior for unhandled traffic, not the function of a specifically configured service.

B. This statement is technically correct as a frame with tags 200.300 would match SAP 1/1/1:200.300 in VPLS 3. However, option E describes a broader rule involving a wildcard, a key QinQ feature likely being tested.

C. This is incorrect. The port is explicitly in qinq mode, and SAPs 1/1/1:100. and 1/1/1:200.300 are configured specifically to accept and process frames with two VLAN tags.

D. This statement is technically correct as a single-tagged frame with VLAN ID 500 would match SAP 1/1/1:500 in VPLS 1. Similar to option B, it describes a valid but specific case.

1. Nokia 7x50 SR OS Services Architecture Guide, R19.10.R1 (3HE15086AAADTQZZA 01), Section: "QinQ Access SAPs", Page 288.

This section details the configuration of SAPs on a port in qinq mode. It explicitly states: "The SAP is specified using the format port-id:s-tag.c-tag or port-id:s-tag. for double-