Before changing the Huawei network configuration, an engineer investigates: A hub iBGP speaker learns a service prefix from a peer but does not re-advertise it to its separate iBGP neighbor. Which diagnostic check should be performed first?
Inspect adjacency graph, route source type and advertisement history on the transit router. This check isolates the suspected cause before an unsafe change. If confirmed, the targeted action is: Use a documented full-mesh or route-reflector design rather than expecting ordinary iBGP transit advertisement. Successful verification is: All intended iBGP peers learn the eligible prefix without loops or unintended repeated announcements.
Check metric-style configuration, TLVs, interface costs and selected SPF paths. This check would diagnose IS-IS metric-style consistency, but would not first isolate the described iBGP split-horizon route propagation. Begin with: Inspect adjacency graph, route source type and advertisement history on the transit router.
Audit security policy order, matching zones and addresses, and permitted-versus-denied test flows. This check would diagnose Default-deny network segmentation, but would not first isolate the described iBGP split-horizon route propagation. Begin with: Inspect adjacency graph, route source type and advertisement history on the transit router.
Inspect configured peer AS, received OPEN messages and BGP neighbor reset reasons. This check would diagnose BGP peer autonomous-system mismatch, but would not first isolate the described iBGP split-horizon route propagation. Begin with: Inspect adjacency graph, route source type and advertisement history on the transit router.
A Huawei Datacom engineer is investigating the following situation: An AS receives an advertised route containing its own AS number and rejects it even though the physical peer is healthy. Which corrective action best resolves the specified issue?
Correct the route propagation or erroneous AS_PATH modification while retaining normal loop prevention. Technical basis: BGP AS_PATH loop detection prevents a route from circulating back through an AS already in its path. The measurable acceptance criterion is: The valid corrected route is accepted and routes still containing the receiver AS are denied.
Examine LSP sequence numbers and lifetime behavior and correct the root flooding or instability problem. This is a legitimate response to the different issue of IS-IS LSP sequence and aging, but it does not correct the specific BGP AS_PATH loop detection condition reported. The relevant technical distinction is: BGP AS_PATH loop detection prevents a route from circulating back through an AS already in its path.
Configure the actual authorized remote AS consistently with the peer's BGP OPEN identity. This is a legitimate response to the different issue of BGP peer autonomous-system mismatch, but it does not correct the specific BGP AS_PATH loop detection condition reported. The relevant technical distinction is: BGP AS_PATH loop detection prevents a route from circulating back through an AS already in its path.
Permit the specifically authorized BGP TCP session over the intended neighbor path and keep unrelated management traffic restricted. This is a legitimate response to the different issue of BGP TCP reachability and port, but it does not correct the specific BGP AS_PATH loop detection condition reported. The relevant technical distinction is: BGP AS_PATH loop detection prevents a route from circulating back through an AS already in its path.
A team is validating a Huawei network repair: An AS receives an advertised route containing its own AS number and rejects it even though the physical peer is healthy. Which observable result provides the clearest evidence of success?
The valid corrected route is accepted and routes still containing the receiver AS are denied. This result directly tests whether the correct action worked: Correct the route propagation or erroneous AS_PATH modification while retaining normal loop prevention. This is explained by: BGP AS_PATH loop detection prevents a route from circulating back through an AS already in its path.
The Level-1 router chooses an intended attached exit and reaches approved remote prefixes. That observation would support a separate case of IS-IS L1 default to nearest attached L1L2, not verification of the reported BGP AS_PATH loop detection. The relevant observable outcome here is: The valid corrected route is accepted and routes still containing the receiver AS are denied.
The receiver obtains group traffic and multicast RPF checks succeed without forwarding loops. That observation would support a separate case of Multicast reverse-path forwarding, not verification of the reported BGP AS_PATH loop detection. The relevant observable outcome here is: The valid corrected route is accepted and routes still containing the receiver AS are denied.
The neighboring AS picks the intended ingress where the MED comparison is applicable. That observation would support a separate case of BGP MED same-neighbor-AS comparison, not verification of the reported BGP AS_PATH loop detection. The relevant observable outcome here is: The valid corrected route is accepted and routes still containing the receiver AS are denied.
Consider the following Huawei Datacom deployment: An AS receives an advertised route containing its own AS number and rejects it even though the physical peer is healthy. Which technical principle best explains the observed behavior?
BGP AS_PATH loop detection prevents a route from circulating back through an AS already in its path. This mechanism explains the case-specific corrective step: Correct the route propagation or erroneous AS_PATH modification while retaining normal loop prevention. Confirm the mechanism by verifying: The valid corrected route is accepted and routes still containing the receiver AS are denied.
EVPN Type 2 carries MAC or MAC/IP reachability; Type 5 is used for IP-prefix reachability. This explains EVPN Type-2 MAC/IP route interpretation, but not why the issue in this scenario occurs. The specific mechanism is: BGP AS_PATH loop detection prevents a route from circulating back through an AS already in its path.
Packet filtering depends on first relevant ACL matches and the direction of filter application. This explains ACL packet filter rule order and direction, but not why the issue in this scenario occurs. The specific mechanism is: BGP AS_PATH loop detection prevents a route from circulating back through an AS already in its path.
IS-IS uses Level-2 routing for inter-area exchange between Level-1 domains. This explains IS-IS level-2 backbone continuity, but not why the issue in this scenario occurs. The specific mechanism is: BGP AS_PATH loop detection prevents a route from circulating back through an AS already in its path.
A Huawei network is left in this condition: An AS receives an advertised route containing its own AS number and rejects it even though the physical peer is healthy. What direct operational or security risk is most relevant if it is not corrected?
Disabling AS loop detection to hide a policy error risks persistent routing loops. This is the direct exposure created by BGP AS_PATH loop detection. Mitigate it through: Correct the route propagation or erroneous AS_PATH modification while retaining normal loop prevention. Then test: The valid corrected route is accepted and routes still containing the receiver AS are denied.
Confusing route types can leave inter-subnet overlay connectivity missing or misconfigured. This consequence is associated more directly with EVPN Type-2 MAC/IP route interpretation. For the stated conditions the immediate exposure is: Disabling AS loop detection to hide a policy error risks persistent routing loops.
A broad PBR match may reroute critical unrelated flows and bypass intended segmentation. This consequence is associated more directly with Policy-based routing for approved application. For the stated conditions the immediate exposure is: Disabling AS loop detection to hide a policy error risks persistent routing loops.
Misconfigured reflector clusters can suppress valid routes or permit duplicate advertisements. This consequence is associated more directly with BGP route reflector cluster loop prevention. For the stated conditions the immediate exposure is: Disabling AS loop detection to hide a policy error risks persistent routing loops.
Before changing the Huawei network configuration, an engineer investigates: An AS receives an advertised route containing its own AS number and rejects it even though the physical peer is healthy. Which diagnostic check should be performed first?
Inspect rejected UPDATE attributes, local AS number and AS_PATH on each advertised prefix. This check isolates the suspected cause before an unsafe change. If confirmed, the targeted action is: Correct the route propagation or erroneous AS_PATH modification while retaining normal loop prevention. Successful verification is: The valid corrected route is accepted and routes still containing the receiver AS are denied.
Inspect candidate AS origins, MED values, higher-priority attributes and effective route-selection rules. This check would diagnose BGP MED same-neighbor-AS comparison, but would not first isolate the described BGP AS_PATH loop detection. Begin with: Inspect rejected UPDATE attributes, local AS number and AS_PATH on each advertised prefix.
Inspect configured peer AS, received OPEN messages and BGP neighbor reset reasons. This check would diagnose BGP peer autonomous-system mismatch, but would not first isolate the described BGP AS_PATH loop detection. Begin with: Inspect rejected UPDATE attributes, local AS number and AS_PATH on each advertised prefix.
Inspect route-policy node IDs, if-match criteria, apply clauses and hit counts. This check would diagnose Route-policy permit and deny node order, but would not first isolate the described BGP AS_PATH loop detection. Begin with: Inspect rejected UPDATE attributes, local AS number and AS_PATH on each advertised prefix.
A Huawei Datacom engineer is investigating the following situation: A partner accidentally prepends the receiving enterprise AS into AS_PATH and its return advertisement is dropped. Which corrective action best resolves the specified issue?
Correct the route propagation or erroneous AS_PATH modification while retaining normal loop prevention. Technical basis: BGP AS_PATH loop detection prevents a route from circulating back through an AS already in its path. The measurable acceptance criterion is: The valid corrected route is accepted and routes still containing the receiver AS are denied.
Restore an appropriate contiguous Level-2 IS-IS inter-area backbone path and verify level participation. This is a legitimate response to the different issue of IS-IS level-2 backbone continuity, but it does not correct the specific BGP AS_PATH loop detection condition reported. The relevant technical distinction is: BGP AS_PATH loop detection prevents a route from circulating back through an AS already in its path.
Run a capacity-focused RF design with appropriate channel reuse, transmit power and channel width. This is a legitimate response to the different issue of High-density WLAN RF plan, but it does not correct the specific BGP AS_PATH loop detection condition reported. The relevant technical distinction is: BGP AS_PATH loop detection prevents a route from circulating back through an AS already in its path.
Classify Type 2 MAC/IP advertisements as endpoint reachability and use Type 5 for supported IP-prefix routing needs. This is a legitimate response to the different issue of EVPN Type-2 MAC/IP route interpretation, but it does not correct the specific BGP AS_PATH loop detection condition reported. The relevant technical distinction is: BGP AS_PATH loop detection prevents a route from circulating back through an AS already in its path.
A team is validating a Huawei network repair: A partner accidentally prepends the receiving enterprise AS into AS_PATH and its return advertisement is dropped. Which observable result provides the clearest evidence of success?
The valid corrected route is accepted and routes still containing the receiver AS are denied. This result directly tests whether the correct action worked: Correct the route propagation or erroneous AS_PATH modification while retaining normal loop prevention. This is explained by: BGP AS_PATH loop detection prevents a route from circulating back through an AS already in its path.
Clients obtain a valid address lease, gateway and DNS options from the authorized remote DHCP server. That observation would support a separate case of DHCP relay to remote server, not verification of the reported BGP AS_PATH loop detection. The relevant observable outcome here is: The valid corrected route is accepted and routes still containing the receiver AS are denied.
One appropriate DIS per active level advertises the LAN pseudonode and the LSDB remains consistent. That observation would support a separate case of IS-IS DIS and pseudonode on broadcast LAN, not verification of the reported BGP AS_PATH loop detection. The relevant observable outcome here is: The valid corrected route is accepted and routes still containing the receiver AS are denied.
The EVPN table shows appropriate host MAC/IP mapping and separately advertised intended IP prefixes. That observation would support a separate case of EVPN Type-2 MAC/IP route interpretation, not verification of the reported BGP AS_PATH loop detection. The relevant observable outcome here is: The valid corrected route is accepted and routes still containing the receiver AS are denied.
Consider the following Huawei Datacom deployment: A partner accidentally prepends the receiving enterprise AS into AS_PATH and its return advertisement is dropped. Which technical principle best explains the observed behavior?
BGP AS_PATH loop detection prevents a route from circulating back through an AS already in its path. This mechanism explains the case-specific corrective step: Correct the route propagation or erroneous AS_PATH modification while retaining normal loop prevention. Confirm the mechanism by verifying: The valid corrected route is accepted and routes still containing the receiver AS are denied.
IS-IS identifies the freshness of LSPs using sequence numbers and lifetime fields. This explains IS-IS LSP sequence and aging, but not why the issue in this scenario occurs. The specific mechanism is: BGP AS_PATH loop detection prevents a route from circulating back through an AS already in its path.
BGP OPEN negotiation validates the expected peer AS and session parameters. This explains BGP peer autonomous-system mismatch, but not why the issue in this scenario occurs. The specific mechanism is: BGP AS_PATH loop detection prevents a route from circulating back through an AS already in its path.
BGP route reflectors use ORIGINATOR_ID and CLUSTER_LIST to prevent reflection loops. This explains BGP route reflector cluster loop prevention, but not why the issue in this scenario occurs. The specific mechanism is: BGP AS_PATH loop detection prevents a route from circulating back through an AS already in its path.
A Huawei network is left in this condition: A partner accidentally prepends the receiving enterprise AS into AS_PATH and its return advertisement is dropped. What direct operational or security risk is most relevant if it is not corrected?
Disabling AS loop detection to hide a policy error risks persistent routing loops. This is the direct exposure created by BGP AS_PATH loop detection. Mitigate it through: Correct the route propagation or erroneous AS_PATH modification while retaining normal loop prevention. Then test: The valid corrected route is accepted and routes still containing the receiver AS are denied.
Using AS_PATH padding without understanding precedence can fail to shift traffic. This consequence is associated more directly with BGP AS_PATH length egress choice. For the stated conditions the immediate exposure is: Disabling AS loop detection to hide a policy error risks persistent routing loops.
A broad PBR match may reroute critical unrelated flows and bypass intended segmentation. This consequence is associated more directly with Policy-based routing for approved application. For the stated conditions the immediate exposure is: Disabling AS loop detection to hide a policy error risks persistent routing loops.
A permissive export filter can leak confidential topology and disrupt other routing domains. This consequence is associated more directly with BGP prefix export-filter leak. For the stated conditions the immediate exposure is: Disabling AS loop detection to hide a policy error risks persistent routing loops.
Before changing the Huawei network configuration, an engineer investigates: A partner accidentally prepends the receiving enterprise AS into AS_PATH and its return advertisement is dropped. Which diagnostic check should be performed first?
Inspect rejected UPDATE attributes, local AS number and AS_PATH on each advertised prefix. This check isolates the suspected cause before an unsafe change. If confirmed, the targeted action is: Correct the route propagation or erroneous AS_PATH modification while retaining normal loop prevention. Successful verification is: The valid corrected route is accepted and routes still containing the receiver AS are denied.
Compare received candidate paths, LOCAL_PREF values, route policy and installed best path. This check would diagnose BGP local preference internal egress, but would not first isolate the described BGP AS_PATH loop detection. Begin with: Inspect rejected UPDATE attributes, local AS number and AS_PATH on each advertised prefix.
Review advertised-route output, prefix-list matches and outbound route-policy order. This check would diagnose BGP prefix export-filter leak, but would not first isolate the described BGP AS_PATH loop detection. Begin with: Inspect rejected UPDATE attributes, local AS number and AS_PATH on each advertised prefix.
Inspect ip-prefix sequence, mask-length qualifiers and test candidate routes. This check would diagnose Prefix-list network and mask matching, but would not first isolate the described BGP AS_PATH loop detection. Begin with: Inspect rejected UPDATE attributes, local AS number and AS_PATH on each advertised prefix.
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