Services

A service provider deploys EVPN with a dual-homed CE connected to two PE routers (PE1 and PE2) using the same Ethernet Segment Identifier (ESI) in all-active redundancy mode. Remote PE3 learns a customer MAC address via an EVPN Type 2 route advertised only by PE1. Operators observe that PE3 load-balances traffic toward the CE across both PE1 and PE2, even though only PE1 advertised the MAC. Which EVPN mechanism enables PE3 to forward toward PE2 for a MAC it never received from PE2?

A service provider deploys EVPN to offer a multi-tenant Ethernet service on their IOS XR PEs. The design team wants a single EVPN Instance (EVI) to carry multiple customer VLANs, where each VLAN maps to its own broadcast domain but all share the same EVI and route targets to conserve control-plane resources. Which EVPN service type must be configured to meet this requirement?

A service provider offers a business-grade Ethernet service to a customer whose CE connects at 1 Gbps physically, but the customer purchased only a 300 Mbps subscription tier. Within that 300 Mbps, voice traffic must receive strict low-latency treatment while remaining data classes share the leftover bandwidth proportionally. On the PE egress interface toward the customer, which QoS mechanism correctly enforces this design?

A service provider is deploying a QoS policy on an IOS XR aggregation router carrying both voice (VoIP) and best-effort internet traffic. The design team wants to guarantee that VoIP experiences minimal latency and jitter even during periods of congestion, while ensuring the voice queue cannot completely starve other traffic classes indefinitely. Which QoS architectural mechanism best meets these requirements?

A service provider offers an EVPL service to a customer using an IOS XR PE router. The customer sends frames tagged with an outer VLAN 100 and inner VLAN 200 (QinQ). The PE must match these double-tagged frames on the access interface, remove the outer service-delimiting VLAN 100 before forwarding across the VPWS pseudowire, and re-impose VLAN 100 toward the customer on egress. Which Ethernet flow point (EFP) configuration on the ingress attachment circuit achieves this behavior?

A service provider runs an EVPN-based L2VPN across its IOS XR core. A dual-homed customer VM is migrated from a server behind PE1 to a server behind PE2. After the move, PE1 continues to advertise the VM's MAC as a local route while PE2 also advertises the same MAC, causing intermittent Layer 2 reachability and MAC flapping between the two PEs. Which EVPN mechanism resolves this by determining which PE currently owns the MAC?

A service provider deploys an EVPN-VPWS service on IOS XR to connect two customer sites across the MPLS core. The customer's CE at Site A is dual-homed to two PEs (PE1 and PE2) using a single LACP bundle (Ethernet Segment). The requirement is that only one PE forwards traffic for the pseudowire at any time, while the other remains as a hot standby that takes over instantly on failure. Which EVPN Ethernet Segment redundancy mode must be configured to meet this requirement?

A service provider offers a multipoint VPLS service to a customer connecting five sites. Recently, one customer site experienced a Layer 2 loop caused by a misconfigured switch, and the resulting MAC learning storm exhausted the PE router's MAC address table for that bridge domain, degrading service for all five sites. The provider wants to limit the impact of a single misbehaving site so that only that site's forwarding is affected while the bridge domain remains stable. Which configuration should the engineer apply on the PE?

A service provider runs a VPLS instance across three PE routers (PE1, PE2, PE3) in a full mesh of pseudowires. A dual-homed customer site connects to PE1 (active) and PE2 (standby) using MST for loop prevention. When the active uplink to PE1 fails and traffic shifts to PE2, remote PE3 continues black-holing customer traffic for the affected MAC addresses until they naturally age out. Which mechanism should be enabled to force PE3 to immediately relearn the MAC addresses on the correct pseudowire?

A service provider deploys a VPLS instance across four PE routers using an LDP-signaled full mesh of pseudowires. During testing, an engineer observes that a broadcast frame injected at PE1 is correctly received by CE devices attached to PE2, PE3, and PE4 exactly once, with no duplicate frames or forwarding loops — even though no spanning tree protocol is running in the provider core. Which VPLS mechanism explains this loop-free behavior across the pseudowire mesh?

You are deploying an EoMPLS point-to-point pseudowire (VPWS) between two IOS XR PE routers across a core that performs equal-cost load balancing based on a deep packet hash. Customers report intermittent packet reordering and dropped frames on the emulated Ethernet circuit, though the pseudowire is up on both ends. What should you configure on the pseudowire to resolve this issue?

A service provider engineer configures a point-to-point EoMPLS (VPWS) pseudowire between two IOS XR PE routers using the l2vpn xconnect group. The attachment circuits are up on both PEs and the targeted LDP session is established, but the pseudowire remains in the DOWN state. On PE1 the interface MTU under the attachment circuit is set to 1500, while on PE2 the corresponding attachment circuit interface MTU is set to 1600. What is the most likely reason the pseudowire fails to come up?

A service provider offers a shared central-services VRF (hosting DNS and NTP servers) that all customer VRFs must reach, but individual customers must NOT be able to reach each other through the central-services VRF. Customer VRFs use RT 65000:100 (customer A) and 65000:200 (customer B). The central-services VRF uses RT 65000:999. Which route-target configuration on the central-services PE VRF achieves the required any-to-central but not customer-to-customer reachability?

A service provider runs an MPLS L3VPN. A PE router imports routes into VRF CUSTOMER-A using route-target import 65000:100. The network team notices that a specific set of customer prefixes tagged with an additional extended community must be prevented from entering the VRF even though they carry RT 65000:100. Which mechanism should be applied on the PE to selectively block those prefixes while continuing to import all other 65000:100 routes?

Two service providers operate separate MPLS L3VPN backbones and must interconnect a customer VPN across their ASBRs. The design team chooses Inter-AS Option B (VPNv4 exchange between ASBRs). On the ASBR of AS 100, VPNv4 routes are being received from the peer ASBR in AS 200, but the customer PE devices in AS 100 cannot forward traffic toward the remote prefixes even though the VPNv4 routes appear in BGP. What must be verified on the AS 100 ASBR for Option B to forward customer traffic correctly?

A service provider runs MP-BGP for its L3VPN backbone. Two PE routers (PE1 and PE2) both have VRF CUSTOMER-A configured with matching route-targets, but CUSTOMER-A routes learned on PE1 are not appearing in the VRF routing table on PE2. On PE2, the command 'show bgp vpnv4 unicast all' shows the VPNv4 prefixes from PE1 are present in the BGP table but are not imported into the VRF. What is the MOST likely cause?

A service provider uses AS 65500 for its MPLS L3VPN backbone. A customer owns two sites that both use the same private AS 65001 for their PE-CE eBGP sessions. Users at Site 1 report they cannot reach any prefixes advertised from Site 2, even though both CE-PE sessions are up and the VPNv4 routes are present on the PEs. What should the provider configure on the PE routers to resolve this?

A service provider runs an MPLS L3VPN for a customer that uses OSPF as the PE-CE routing protocol at two sites, Site A and Site B. Both sites also have a direct backdoor OSPF link between them within the same OSPF area. The customer complains that traffic between the two sites always takes the low-speed backdoor link instead of the high-speed MPLS backbone. The PEs redistribute customer routes into MP-BGP and back into OSPF as type-3 inter-area routes. What must the SP engineer configure to make the MPLS backbone the preferred path?

A service provider runs MPLS L3VPN with OSPF as the PE-CE routing protocol for customer ACME. Routes learned from a remote CE via MP-BGP are redistributed back into OSPF on the local PE toward the CE. The customer complains that these VPN routes appear on their CE routers as OSPF external Type 5 (E2) LSAs, but they require the routes to be seen as inter-area (Type 3) summary LSAs so that internal SPF metric behavior is preserved end-to-end. Both customer sites use the same OSPF process and are in different, non-zero areas connected through the MPLS backbone. What must be configured on the PEs to achieve this?

A service provider runs an MPLS L3VPN for a customer that uses RIPv2 as the PE-CE routing protocol on both sites. On PE1, the VRF 'CUST-A' learns customer routes from the CE via RIPv2 and redistributes them into MP-BGP. At the remote PE2, these routes are received via VPNv4 and must be redistributed back into RIPv2 toward the remote CE. After configuration, PE2 advertises the routes to its CE but the remote CE marks them as unreachable. Which action on PE2 resolves the problem?