H12-891 Hcie-Datacom Practice Questions

SRv6 achieves source routing by placing an ordered list of segments (SIDs) into a new IPv6 extension header called the Segment Routing Header (SRH). The ingress node populates the SRH with the SIDs corresponding to nodes B, C, and D. As the packet traverses the network, each node processes the active segment in the list and forwards the packet to the next segment, effectively steering it along the predefined explicit path.

The display gre statistics command is a powerful troubleshooting tool that shows counters for encapsulated and decapsulated GRE packets. If the 'Encapsulated' counter is increasing but the 'Decapsulated' counter on the remote router is zero, it suggests a reachability issue or a firewall blocking GRE protocol 47. If neither counter increases, it points to a routing problem where traffic isn't being directed to the tunnel interface.

Priority Queuing (PQ) provides strict priority scheduling, where packets in the highest-priority queue are always serviced first. Low Latency Queuing (LLQ) is a variation that combines PQ with CBWFQ, giving strict priority to a class (like voice) up to a configured bandwidth limit to prevent starvation of other queues. Both are designed to provide the lowest latency for real-time traffic like VoIP.

A key feature of NETCONF is its robust transaction model based on distinct configuration datastores, such as , , and . This allows for safer configuration changes with commit and rollback capabilities. While RESTCONF can access these datastores, the concept is native to NETCONF's design. RESTCONF is an HTTP-based protocol that maps REST verbs (GET, POST, PUT, DELETE) to YANG data models, typically supporting both XML and JSON.

In Huawei's VRP, if a route matches the if-match clauses of a route-policy node but there is no explicit apply clause or permit/deny keyword, the default behavior for that node is to permit the route. This is an important distinction from some other vendor implementations and can lead to unexpected behavior if not understood.

In an EVPN fabric, the Type 2 route is used to advertise the reachability of individual end systems (hosts). It carries both the MAC address and, optionally, the IP address of the host, allowing other VTEPs to learn these bindings. This is fundamental for forwarding both Layer 2 and Layer 3 traffic within the VXLAN overlay.

The m.get() method is used for retrieving operational state data, distinct from m.get_config() which retrieves configuration data. The correct approach is to use a subtree filter specifying the YANG model path to the desired operational data, in this case, the BGP peers. The XML filter needs the correct namespace to identify the YANG module.

The filter-lsa-out command, applied on an ABR within the area configuration, is the specific mechanism designed to filter Type 3 and Type 5 LSAs from being advertised into that area. This directly manipulates the LSA advertisement at the area boundary, which is more efficient than filtering routes after they have been calculated from the LSAs.

802.1X is the standard for port-based network access control, providing strong, credential-based authentication suitable for corporate employees.

Portal authentication (or captive portal) redirects users to a web page for login, which is ideal for guest access as it does not require any pre-configured client software.

MAC address authentication is used for devices that do not support 802.1X, such as printers or IoT sensors. It authenticates the device based on its unique hardware MAC address.

The SRGB is a locally significant range of labels that each router reserves for use by Segment Routing. Global SIDs, like Prefix-SIDs advertised by IGP, are mapped to a label within this block. For SR to function correctly, all routers in the domain should ideally be configured with the same SRGB range.