When a BGP session is stuck in the Active state, it indicates the local router is trying to initiate a TCP connection (by sending SYN packets) but is not succeeding. While all options can cause BGP issues, a firewall filter blocking the destination port (179) on the remote peer would precisely cause the local router to continuously retry the connection, remaining in Active. A misconfigured AS number typically causes the session to cycle between Idle and Active. A down loopback would likely keep the state as Idle. Mismatched timers allow the session to reach Established before failing.

In Junos, OSPF external routes (Type 5 and Type 7 LSAs) are not considered part of the OSPF protocol’s routing table for redistribution by default. Only internal OSPF routes (intra-area and inter-area) are eligible. To redistribute external routes, the policy must explicitly match them using ‘from protocol ospf external’ or the global routing-options configuration must include ‘ospf export-advertise-protocol-eligible-external’ to make them eligible for redistribution in the first place.

LDP builds its LSPs based on the IGP’s shortest path. If an LSP takes a suboptimal path, it’s because LDP does not have an adjacency on one or more links along the IGP’s preferred path. Therefore, the LSP must detour via a path where LDP sessions are fully established. The first step is to ensure LDP is configured on all interfaces along the IGP-calculated optimal route. ‘igp sync’ deals with IGP-LDP synchronization warnings, not path selection. RSVP policies would not affect pure LDP LSPs.

For an IRB interface to perform Layer 3 routing in an EVPN-VXLAN fabric, it must be associated with a bridge domain (and thus a VLAN) within a routing instance (usually of type ‘virtual-switch’ or ‘default-switch’). If the IRB interface is not correctly placed in the routing instance and associated with the bridge domain, it cannot forward traffic between VLANs, even if it has the necessary MAC/IP information. The other options are not standard requirements for basic IRB functionality in this context.

A Route Reflector (RR) appends the ORIGINATOR_ID attribute, which is the Router ID of the originator of the route in the local AS. When a router (client or non-client) receives a route with an ORIGINATOR_ID that matches its own Router ID, it must discard the route to prevent a loop. While CLUSTER_LIST (checked against the local cluster-id) is also used, the question asks for an attribute *manipulated by the RR* that clients check. The RR creates/updates the ORIGINATOR_ID.

The IS-IS Overload bit is set to inform other routers not to use this router as a transit point for traffic, while still allowing connectivity to its directly connected networks. This is commonly done during router boot-up or major configuration changes to prevent the router from attracting transit traffic before its routing table is fully stable. It can be set manually for maintenance or triggered automatically if certain system thresholds (like CPU) are exceeded, depending on configuration.

In Junos BGP configuration, policies applied directly at the neighbor level (under the specific neighbor’s configuration) take precedence and override policies configured at the group level for that specific neighbor. The neighbor-level policy is used exclusively; the group-level policy is ignored for that peer. This allows for efficient group-level defaults with specific exceptions for individual peers.

The Provider Edge (PE) router performs the critical function of VPN route conversion. It learns standard IPv4 routes from the Customer Edge (CE) router via a routing protocol (e.g., BGP, OSPF, static). The PE then prepends a unique Route Distinguisher (RD) to each customer route, creating a VPN-IPv4 (VPNv4) address family route. This VPNv4 route is then advertised via MP-BGP to other PE routers. P routers and RRs do not attach RDs; they handle labeled packets or reflect VPNv4 routes, respectively.

For inbound traffic engineering from an EBGP peer, manipulating the AS_PATH is a common and effective method. By artificially lengthening (prepending) your own AS number in the AS_PATH of the aggregate route, you make that route less preferable compared to the specific routes which have a shorter AS_PATH length. The peer’s BGP best path selection algorithm will prefer the shorter path (the specific routes) for forwarding traffic. LOCAL_PREF and MED are non-transitive and typically used for influence within an AS or between neighboring ASs with a specific agreement, respectively.

When a BGP session is stuck in the Active state, it indicates the local router is trying to initiate a TCP connection (by sending SYN packets) but is not succeeding. While all options can cause BGP issues, a firewall filter blocking the destination port (179) on the remote peer would precisely cause the local router to continuously retry the connection, remaining in Active. A misconfigured AS number typically causes the session to cycle between Idle and Active. A down loopback would likely keep the state as Idle. Mismatched timers allow the session to reach Established before failing.0