802.1Q VLANs are the standard and most efficient technology for creating Layer 2 broadcast domain isolation within a shared physical infrastructure. They allow multiple departments to be segmented on the same switches while using a common router (or Layer 3 switch) for inter-VLAN routing, perfectly matching the scenario’s requirements.

The EXSTART state is where routers establish a master/slave relationship and begin to exchange Database Description (DBD) packets. If the MTU is mismatched, the larger DBD packets may be dropped, preventing the adjacency from progressing. This is a common and subtle issue that fits the symptoms described.

The critical difference is control and predictability. The ‘network’ command only advertises a prefix if an exact match exists in the router’s routing table (from any source). Redistribution automatically advertises all IGP routes, which can lead to unintended advertisements and is less precise. Professional designs often favor the explicit ‘network’ command for critical prefixes.

MPLS L3VPN is the industry-standard solution for large-scale, hub-and-spoke or any-to-any enterprise WANs. It natively provides segmentation (VRFs), supports dynamic routing protocols (PE-CE routing) like OSPF or BGP, and relies on the service provider’s MPLS core for traffic separation, meeting all the bank’s requirements for scalability, security, and dynamic routing.

BGP has a strict rule: before a BGP route can be considered valid and installed in the routing table, its next-hop attribute must be reachable via an existing route in the IP routing table. This is often the cause when a route is ‘seen’ in the BGP table but not used for forwarding.

Link Aggregation Control Protocol (LACP) and static Eth-Trunk both require that all member physical links are connected between the same two devices (or network nodes). Connecting them to different devices would break the fundamental logic of the bundle, causing severe traffic loss and hashing problems.

In OSPF, inter-area route summarization is performed on the Area Border Router (ABR). The command ‘area [area-id] range [ip-address] [mask]’ is the specific and correct method to summarize routes from a specific area (Area 1) before they are advertised into another area (Area 0).

LDP’s core function is to automatically build the label-forwarding tables (LFIB) in MPLS routers. It does this by binding IP prefixes to labels and distributing these bindings to neighboring LSRs, thereby establishing the unidirectional Label Switched Paths (LSPs) that enable MPLS forwarding.

Low Latency Queuing (LLQ) is the recommended Huawei/ Cisco QoS mechanism for real-time traffic like voice. It provides a strict priority queue (for EF traffic) that is serviced first, guaranteeing low latency and jitter. It also incorporates policing to prevent the priority queue from starving other traffic, making it the correct choice for a bandwidth guarantee.

802.1Q VLANs are the standard and most efficient technology for creating Layer 2 broadcast domain isolation within a shared physical infrastructure. They allow multiple departments to be segmented on the same switches while using a common router (or Layer 3 switch) for inter-VLAN routing, perfectly matching the scenario’s requirements.0