300-510 SPRI: Implementing Cisco Service Provider Advanced Routing SolutionsDemo

Traditional Cisco Auto-RP relies on dense-mode flooding of its RP-Announcement and RP-Discovery control groups so routers can learn dynamic group-to-RP mappings. Consequently, PIM-enabled interfaces must be configured for sparse-dense mode (unless an alternative Auto-RP listener design is explicitly configured). A Bootstrap Router (BSR) is a different RP-discovery mechanism.

BGP standard communities are 32-bit values. Cisco IOS displays them as a decimal number by default, whereas ip bgp-community new-format displays them in AA:NN format. R1’s decimal communities correspond to R2’s AA:NN communities, so enabling the new display format on R1 makes the outputs match. This affects display format, not community advertisement or exchange.

SR Tree-SID builds an SR point-to-multipoint multicast replication tree. A replication segment forwards and replicates traffic toward the required downstream nodes, enabling efficient multicast delivery across the SR core without using traditional multicast control protocols such as RSVP, mLDP, or PIM.

Router C, acting as RR2, must advertise routes with itself as the BGP next hop so RR2 clients can forward through the reflector when they do not have the required direct iBGP relationship. This preserves route reflection for F, while D and E retain their direct iBGP peering. Disabling client-to-client reflection would suppress necessary reflected updates to non-meshed clients such as F.

The prefix 2001:DB8:1:1/128 is originated by R1 with SID 110. R2 advertises the reachable prefix using its associated SID 110; R2’s node SID 120 identifies R2 itself rather than R1’s prefix.

A service SID with service instructions identifies a service function for Segment Routing service chaining, causing packets to be processed by the associated ASA. Node SIDs, adjacency SIDs, and prefix SIDs identify network reachability or path elements rather than a service function.

SRv6 IS-IS Flexible Algorithm automatically provides traffic delivery over a traffic-engineered path computed by the IGP for destinations reachable through that IGP. The algorithm can apply configured metrics and constraints during path computation, but its resulting forwarding behavior is the automatically computed engineered path.

SR-MPLS requires MPLS data-plane support before Segment Routing is enabled. IS-IS can distribute Segment Routing information in an IGP deployment, but it is not the required prerequisite in every deployment; EIGRP and explicit-null configuration are not prerequisites.

Redistributing Level 2 routes into Level 1 at R3 makes the MAN-hosted platform prefixes reachable from the Level 1 area through R3 and its higher-bandwidth 100 Mbps connection. Summarizing 64.45.52.0/22 into Level 1 at R3 advertises a single aggregate instead of the individual platform routes, reducing routing-table and memory consumption on Level 1 routers. Cisco documents summary-address address mask level-1 as the form that summarizes routes redistributed into Level 1 IS-IS.

The SRGB must be the common 16000–23999 range so node-SID indexes resolve consistently throughout the domain. Adjacency SIDs are locally significant segments and must be allocated from the configured SRLB; therefore, the adjacency-SID label range must cover 1002–6005. The specified per-router adjacency alternatives use labels belonging to different outgoing adjacencies.

A PCE centrally collects network topology information to compute SR-TE paths. IS-IS distribute link-state exports IS-IS nodes, links, and prefixes to BGP-LS, and the BGP-LS neighbor to the PCE address supplies that topology to the PCE. Router 2 is therefore a topology-information source for Router 1.

BGP member AS 65000 must configure AS 65001 as a confederation peer for the inter-member BGP session. Confederation peers are special eBGP peers that exchange routes within the confederation while the confederation identifier, AS 10, is presented outside it. Configuring bgp confederation peers 65001 under BGP AS 65000 on RM restores the required AS65000-to-AS65001 path.

An SR-TE tunnel is configured at its headend, and the destination 192.168.1.2 command identifies its endpoint. The path-option 12 dynamic segment-routing setting creates a dynamically computed Segment Routing path; it is not an explicitly configured label list and does not make the tunnel bidirectional.

OSPF is a Layer 3 protocol that runs directly over IP, using IP protocol number 89 for its packets. IS-IS, by contrast, is an OSI-based protocol that operates directly over the data-link layer independent of IP; on Ethernet segments its PDUs are carried in IEEE 802.3/802.2 LLC frames rather than being encapsulated in IP. This fundamental encapsulation difference is well documented in comparisons of the two protocols.

Separately, the two protocols differ in how their designated-router role is maintained. OSPF's Designated Router (DR) election is non-preemptive — once a DR is elected on a segment, it keeps that role even if a router with a higher OSPF priority later joins the network; a new election only occurs if the existing DR fails. IS-IS's Designated Intermediate System (DIS) election, however, is preemptive — if a router with a higher interface priority joins the LAN at any point, it immediately takes over the DIS role, regardless of whether the current DIS is still functioning, purging the old pseudonode LSP and reflooding new LSPs.

The other options misstate actual protocol behavior: OSPF fully (not partially) refreshes its LSA database every 30 minutes while IS-IS's default LSP refresh interval is 15 minutes (not 60); an OSPF Area Border Router can belong to multiple areas while an IS-IS router belongs to only one area (the reverse of what is stated); and OSPF's default administrative distance is 110 while IS-IS's is 115 (also reversed in that option).

Dynamic 6to4 tunneling uses the 2002::/16 IPv6 prefix. The next 32 bits encode the destination router’s IPv4 address, allowing the tunnel endpoint to be derived dynamically.

Disabling intra-cluster client-to-client route reflection prevents the route reflector from passing routes learned from one client to other clients in that cluster. The clients must therefore be fully meshed with iBGP peerings so they can exchange the prefixes directly.

The log entries show that R2's BGP session to neighbor 10.0.0.1 (R1) was torn down because the number of received VPNv4 prefixes (1560) exceeded the configured maximum-prefix limit (1500). This is a standard BGP maximum-prefix protection mechanism, and once triggered it drops the peering (and any associated VPNv4/MDT topologies) until the condition is manually cleared and, if the true prefix count is legitimately higher, the limit is raised. Because R2 functions as the ABR/route-reflector point between OSPF 100 and the rest of the Unified MPLS core, losing that VPNv4 session prevents propagation of L3VPN routes between OSPF 100 and OSPF 200/300, while OSPF 100's own internal Unified MPLS LSPs/services remain unaffected since they do not depend on that BGP session. The fix is to raise the maximum-prefix limit on R2 for that neighbor to at least 1560 (or higher) so the session can stay up and carry the additional prefixes introduced by the new data center.

A static 0.0.0.0/0 route is not advertised into an IS-IS domain by redistribute static. Under the IS-IS routing process, default-information originate is required to generate and advertise the default route.

On an OSPF broadcast network, routers establish full adjacencies only with the designated router (DR) and backup designated router (BDR). A router that is neither is a DROTHER and normally remains in the 2-Way state with other DROTHER routers, reducing unnecessary database synchronization and LSA flooding.

segment-routing sr-prefer prefix-list selectively makes SR labels preferred over LDP labels for prefixes that match the configured prefix list. The bank branch is in the 10.20.20.0/24 network, so configuring this preference on CR1 and CR2 for 10.20.20.10/24 ensures the enterprise path to the branch uses segment routing without broadly changing label preference for mobility traffic.

The _65517_ AS-path regular expression matches AS 65517 anywhere as a complete AS number in the path, so it identifies routes that have passed through AS 65517. The inbound permit route-map sequence accepts those matching routes and sets their local preference to 150.

PIM-SSM relies on receivers sending source-specific multicast membership reports for a particular source and group. IGMPv3 provides this source-filtering capability; PIM-SSM does not require an RP or PIM dense mode.

MED is advertised to an external BGP peer to express the preferred path into the advertising autonomous system; a lower MED is preferred. Local preference is confined to the local AS, weight is local to the router, and an IGP metric alone does not enable BGP load balancing. MED values from different neighboring ASes require explicit configuration on the receiving router for cross-AS MED comparison.