3.1 Layer 2 Infrastructure
Layer 2 forms the switching fabric of every campus network. The ENCOR exam tests your ability to troubleshoot trunking, EtherChannel, and Spanning Tree — three technologies that must work together flawlessly.
VLANs and 802.1Q Trunking
A VLAN (Virtual LAN) segments a physical switch into isolated broadcast domains. 802.1Q trunking carries traffic for multiple VLANs across a single link by inserting a 4-byte tag (TPID 0x8100 + 12-bit VLAN ID) between the source MAC and EtherType fields.
- Native VLAN: traffic sent untagged on a trunk (default VLAN 1 — change for security)
- Allowed VLANs: list of VLANs permitted to traverse the trunk
- DTP (Dynamic Trunking Protocol): Cisco proprietary — auto-negotiates trunk. Disable on edge ports with
switchport nonegotiate - VTP (VLAN Trunking Protocol): propagates VLAN database. VTP v3 supports extended VLANs (1006–4094) and MST configuration
Common trunk failures: native VLAN mismatch (generates CDP warnings), allowed VLAN pruning, DTP mode mismatch (dynamic auto ↔ dynamic auto = access), encapsulation mismatch on older platforms.
EtherChannel (LACP / PAgP / Static)
EtherChannel bundles 2–8 (IOS) or 2–16 (LACP standard) physical links into one logical interface (port-channel). STP sees a single link — no blocking. Load is distributed per-flow using a hashing algorithm (src-dst-IP, src-dst-MAC, etc.).
| Protocol | Standard | Modes | Negotiation | Key Detail |
|---|---|---|---|---|
| LACP | IEEE 802.3ad | active / passive | Yes — sends LACP PDUs | active+active or active+passive form channel |
| PAgP | Cisco proprietary | desirable / auto | Yes — sends PAgP PDUs | desirable+desirable or desirable+auto |
| Static (on) | — | on | No | Both sides must be on; no negotiation — risky |
All member ports must match: speed, duplex, mode (access/trunk), native VLAN, allowed VLANs, STP settings. A mismatch suspends the port-channel. Use
show etherchannel summary — look for (P)=bundled, (I)=standalone, (s)=suspended.Spanning Tree: RSTP and MST
RSTP (802.1w) — Rapid Spanning Tree Protocol — converges in ~1–2 seconds vs. 30–50 seconds for legacy 802.1D. Cisco implements it as Rapid PVST+ (one RSTP instance per VLAN).
| Port Role | RSTP State | Description |
|---|---|---|
| Root Port | Forwarding | Best path to Root Bridge (one per non-root switch) |
| Designated Port | Forwarding | Best port on each segment toward the Root Bridge |
| Alternate Port | Discarding | Backup path to Root Bridge (replaces Blocking in 802.1D) |
| Backup Port | Discarding | Redundant path on same segment (hub scenario) |
| Edge Port | Forwarding (immediate) | PortFast-enabled — never transitions through sync |
MST (802.1s) — Multiple Spanning Tree — maps multiple VLANs to a single STP instance (MSTI), reducing CPU/memory vs. Rapid PVST+. Requires all switches in an MST region to share the same: region name, revision number, and VLAN-to-instance mapping.
| Feature | 802.1D (STP) | 802.1w (RSTP) | 802.1s (MST) |
|---|---|---|---|
| Convergence | 30–50 sec | 1–2 sec | 1–2 sec |
| Instances | 1 (CST) | 1 per VLAN (PVST+) | 1 per MSTI (user-defined) |
| Port States | 5 (Block/Listen/Learn/Fwd/Disabled) | 3 (Discarding/Learning/Forwarding) | 3 (same as RSTP) |
| Topology Change | TC notification + 15s delay | Immediate flush MACs | Immediate flush MACs |
| CPU Overhead | High (per-VLAN) | High (per-VLAN) | Low (shared instances) |
STP Protection: Root Guard, BPDU Guard and Loop Guard
The blueprint calls for Spanning Tree enhancements alongside RSTP and MST. Three guards cover almost every question, and the distinction between them is what gets tested.
| Feature | Applied to | Triggered by | Result |
|---|---|---|---|
| Root guard | Designated ports facing other switches | A superior BPDU arriving | Port moves to root-inconsistent (blocking) until the superior BPDU stops |
| BPDU guard | PortFast edge ports facing hosts | Any BPDU arriving | Port is err-disabled |
| Loop guard | Root and alternate ports | BPDUs stopping unexpectedly | Port moves to loop-inconsistent instead of forwarding |
SW1(config)# interface GigabitEthernet0/1 SW1(config-if)# spanning-tree guard root ! protect the root bridge election SW1(config)# interface GigabitEthernet0/10 SW1(config-if)# spanning-tree portfast SW1(config-if)# spanning-tree bpduguard enable SW1(config)# spanning-tree loopguard default ! all point-to-point links SW1# show spanning-tree inconsistentports SW1# show spanning-tree summary
Root guard keeps a switch from becoming the root; the port still passes traffic once the superior BPDUs stop, and it recovers on its own. BPDU guard assumes no switch should exist there at all and err-disables the port, which needs manual recovery or
errdisable recovery cause bpduguard.3.2 Layer 3 Routing
Section 3.2 covers EIGRP, OSPF and OSPFv3, eBGP, and policy-based routing. These are the backbone of enterprise IP routing. The exam tests conceptual comparison, configuration, and troubleshooting across all four areas.
EIGRP (Enhanced Interior Gateway Routing Protocol)
EIGRP is Cisco’s advanced distance-vector protocol using the DUAL (Diffusing Update Algorithm). It sends partial, bounded updates only when topology changes occur — far more efficient than RIP’s periodic full-table updates.
| Parameter | EIGRP Value | Notes |
|---|---|---|
| Protocol | IP Protocol 88 | Multicast 224.0.0.10 |
| AD | 90 (internal) / 170 (external) | Redistributed routes = 170 |
| Metric | Composite: BW + Delay (+ Load, Reliability optional) | K1=1,K3=1 by default; K2,K4,K5=0 |
| Hello/Hold | 5s/15s (LAN) · 60s/180s (WAN) | Must match to form adjacency |
| Load Balancing | Equal AND unequal path | variance command for unequal |
| Successor | Best path to destination | Installed in routing table |
| Feasible Successor | Backup path meeting FC | FC: neighbor RD < local FD |
If no Feasible Successor exists, EIGRP goes Active — sends QUERY messages to neighbors. If all replies received → Passive (converged). Stuck-in-Active (SIA) after 3 min = neighbor relationship reset. Use
show ip eigrp topology to see Successor/FS and FD/AD values.OSPF Multi-Area
OSPF is a link-state IGP using the Dijkstra SPF algorithm. All areas must connect to Area 0 (backbone). Inter-area routing flows through ABRs (Area Border Routers).
| LSA Type | Name | Generated By | Scope |
|---|---|---|---|
| Type 1 | Router LSA | Every router | Within area |
| Type 2 | Network LSA | DR on broadcast segment | Within area |
| Type 3 | Summary LSA | ABR | Inter-area |
| Type 4 | ASBR Summary | ABR | Inter-area (points to ASBR) |
| Type 5 | External LSA | ASBR | Entire OSPF domain |
| Type 7 | NSSA External | ASBR in NSSA | Within NSSA, converted to Type 5 at ABR |
| Area Type | Blocks | Config Command |
|---|---|---|
| Regular | Nothing | (default) |
| Stub | Type 4, 5 (external LSAs) | area X stub |
| Totally Stub | Type 3, 4, 5 | area X stub no-summary |
| NSSA | Type 5; allows Type 7 | area X nssa |
| Totally NSSA | Type 3, 4, 5; allows Type 7 | area X nssa no-summary |
On multi-access segments (Ethernet), OSPF elects a DR and BDR to reduce LSA flooding. DR uses 224.0.0.6; all routers use 224.0.0.5. Election: highest interface priority (default 1), then highest Router-ID. Priority 0 = ineligible. Election is non-preemptive — clear process with
clear ip ospf process to force re-election.OSPFv3 — OSPF for IPv6 (and IPv4)
OSPFv3 is a separate protocol from OSPFv2, not merely an address-family bolt-on. The algorithm, areas, LSA flooding and DR/BDR election are identical; what changes is the transport and how addressing is handled.
| OSPFv2 | OSPFv3 | |
|---|---|---|
| RFC | 2328 | 5340 |
| Carries | IPv4 only | IPv6 and IPv4 (address families) |
| Runs over | IPv4, protocol 89 | IPv6, next header 89, using link-local source |
| Multicast | 224.0.0.5 / 224.0.0.6 | FF02::5 / FF02::6 |
| Adjacency on | Matching subnet required | Link-local — subnets need not match |
| Authentication | Built in (plain, MD5) | Delegated to IPsec (AH/ESP) |
| Enabled by | network statement |
Per interface |
| Router-ID | 32-bit, may be auto-derived | 32-bit, must be configured if no IPv4 exists |
! OSPFv3 with address families (IOS-XE) R1(config)# router ospfv3 1 R1(config-router)# router-id 1.1.1.1 ! mandatory on an IPv6-only router R1(config-router)# address-family ipv6 unicast R1(config-router-af)# exit-address-family R1(config)# interface GigabitEthernet0/0 R1(config-if)# ipv6 address 2001:db8:acad::1/64 R1(config-if)# ospfv3 1 ipv6 area 0 ! enabled per interface, not via network R1# show ospfv3 neighbor R1# show ospfv3 interface brief
OSPFv3 still uses a 32-bit router-ID written in dotted-decimal. On a router with no IPv4 address anywhere there is nothing to derive it from, so the process will not start until
router-id is set manually.eBGP (External BGP)
BGP is the internet’s routing protocol — a path-vector EGP that routes between Autonomous Systems (AS). In enterprises, eBGP peers with ISPs or connects SD-WAN underlay paths. Unlike IGPs, BGP doesn’t auto-discover neighbors; peers must be explicitly configured.
| Attribute | Type | Description | Scope |
|---|---|---|---|
| Weight | Cisco local | Highest preferred for outbound (local router only) | Router-local |
| Local Preference | Well-known discretionary | Highest preferred for outbound (within AS) | iBGP |
| AS-Path | Well-known mandatory | Shortest preferred; loop prevention | eBGP |
| MED | Optional non-transitive | Lowest preferred for inbound (hint to neighbor AS) | eBGP |
| Origin | Well-known mandatory | i < e < ? (IGP < EGP < incomplete) | All |
| Next-Hop | Well-known mandatory | eBGP: set to self. iBGP: not changed by default | All |
BGP Best-Path Selection Order (mnemonic: “We Love Oranges AS Oranges Mean Pure Refreshment”): Weight → Local Pref → Locally originated → AS-Path (shortest) → Origin → MED → eBGP over iBGP → IGP metric to Next-Hop → Router-ID
eBGP sets IP TTL=1 by default — peers must be directly connected. Use
neighbor X.X.X.X ebgp-multihop <ttl> for non-directly-connected peers (loopback-based peering). iBGP uses TTL=255.Policy-Based Routing (PBR)
Normal forwarding looks only at the destination address. Policy-based routing overrides that, letting a route-map choose the next hop based on source address, protocol, port, or packet size — routing by policy rather than by destination alone.
! Send guest traffic out the broadband link, everything else routes normally R1(config)# ip access-list extended GUEST-TRAFFIC R1(config-ext-nacl)# permit ip 192.168.50.0 0.0.0.255 any R1(config)# route-map PBR-GUEST permit 10 R1(config-route-map)# match ip address GUEST-TRAFFIC R1(config-route-map)# set ip next-hop 203.0.113.2 R1(config-route-map)# exit ! empty permit = everything else routes normally R1(config)# route-map PBR-GUEST permit 20 R1(config)# interface GigabitEthernet0/1 R1(config-if)# ip policy route-map PBR-GUEST ! INBOUND, on ingress R1# show ip policy R1# debug ip policy
set ip next-hop— forces the next hop, taking precedence over the routing tableset ip default next-hop— used only if the routing table has no routeset interface— forces an egress interfaceip local policy route-map— applies PBR to traffic generated by the router itself
A route-map ends with an implicit deny, but in PBR “deny” means do not apply policy rather than drop — unmatched traffic falls through to normal routing. The empty
permit 20 makes that explicit and is good practice.3.3 IP Services
NTP (Network Time Protocol)
NTP synchronizes clocks across devices using a hierarchical stratum model. Accurate time is critical for log correlation, certificate validity, and SNMP timestamps.
| Stratum | Description | Example |
|---|---|---|
| 0 | Reference clock (atomic, GPS) | GPS receiver, cesium clock |
| 1 | Directly connected to stratum 0 | NTP primary servers (time.nist.gov) |
| 2 | Synced from stratum 1 | Enterprise NTP server |
| 3–15 | Downstream clients/servers | Routers, switches, firewalls |
| 16 | Unsynchronized | Device not yet synced or NTP disabled |
- NTP authentication: MD5-based; configure matching key on server and client
- NTP master: Makes the router act as an authoritative source (even without upstream sync) — use with caution
- Verify with:
show ntp status,show ntp associations
PTP (Precision Time Protocol, IEEE 1588)
NTP synchronises to within milliseconds, which is fine for log correlation. PTP reaches sub-microsecond accuracy by timestamping in hardware and measuring the delay of each link, which is what industrial, financial and broadcast networks need.
| NTP | PTP (1588) | |
|---|---|---|
| Accuracy | Milliseconds | Sub-microsecond |
| Timestamping | Software | Hardware, at the PHY |
| Transport | UDP 123 | UDP 319 (event) / 320 (general), or Layer 2 |
| Hierarchy | Stratum 0–16 | Grandmaster, boundary, transparent, ordinary clocks |
| Master selection | Configured | Best Master Clock Algorithm (BMCA), automatic |
| Typical use | Logging, certificates | Industrial control, financial trading, broadcast |
SW1(config)# ptp mode boundary SW1(config)# ptp domain 0 SW1(config)# interface GigabitEthernet1/0/1 SW1(config-if)# ptp enable SW1# show ptp clock SW1# show ptp parent ! which grandmaster this clock follows SW1# show ptp port
A boundary clock terminates PTP and becomes a master to devices below it. A transparent clock forwards PTP messages but writes its own queuing delay into the correction field, so downstream clocks can subtract it. Both remove the switch from being a source of error.
NAT / PAT
NAT (Network Address Translation) translates private RFC 1918 addresses to public IPs. Essential for IPv4 address conservation and ISP connectivity.
| NAT Type | Description | Use Case |
|---|---|---|
| Static NAT | One-to-one: fixed private ↔ public mapping | Servers (web, mail) needing consistent public IP |
| Dynamic NAT | Many-to-many: pool of public IPs, first-come-first-served | Outbound internet with IP pool |
| PAT (NAT Overload) | Many-to-one: all private hosts share one public IP via port numbers | Home/branch internet (most common) |
| Policy NAT | NAT applied only when route-map conditions match | Multi-ISP, VPN exclusion |
ip nat inside source translates the source of packets coming FROM inside TO outside. “Inside local” = private IP. “Inside global” = public IP seen on outside. show ip nat translations and show ip nat statistics are key verification commands.Multicast — IGMP and PIM
Multicast delivers one stream to many receivers efficiently. Hosts use IGMP to join multicast groups; routers use PIM to build delivery trees.
| Component | Version/Mode | Key Behavior |
|---|---|---|
| IGMP v1 | Legacy | Join only — no leave; 3-min timeout |
| IGMP v2 | Common | Adds Leave Group message for faster pruning (~3 sec) |
| IGMP v3 | Modern | Source-specific joins (SSM) — host specifies source IP |
| MLD | IPv6 equivalent | MLDv1≈IGMPv2, MLDv2≈IGMPv3 |
| PIM Dense Mode | Push model | Flood-and-prune; good for dense receiver populations |
| PIM Sparse Mode | Pull model | RP-based; receivers explicitly join; enterprise standard |
| PIM SSM | Source-Specific | No RP needed; uses 232.0.0.0/8; requires IGMPv3 |
| BIDIR-PIM | Bidirectional | Bidirectional tree; many-to-many; no SPT switchover |
Rendezvous Point (RP) discovery methods:
- Static RP:
ip pim rp-address— simple, no redundancy without Anycast RP - Auto-RP: Cisco proprietary — Candidate-RP announces to 224.0.1.39; Mapping Agent listens and floods to 224.0.1.40
- BSR (Bootstrap Router): RFC standard — Candidate-RPs register with BSR; BSR floods RP-Set to all PIM routers
- Anycast RP + MSDP: Multiple RPs share same IP address; MSDP synchronizes active sources between them
If a multicast packet fails the RPF check, it is dropped — this is the most common multicast troubleshooting issue. Use
show ip rpf <source-ip> to verify which interface RPF expects packets from. Asymmetric unicast routing causes RPF failures.First Hop Redundancy Protocols in IP Services
FHRPs give hosts a default gateway that survives the failure of any one router, by sharing a virtual IP and virtual MAC between two or more routers. The design rationale sits in 1.1.b; this is the configuration and verification view the blueprint asks for under IP Services.
| HSRP | VRRP | GLBP | |
|---|---|---|---|
| Standard | Cisco proprietary | Open (RFC 5798) | Cisco proprietary |
| Roles | Active / Standby | Master / Backup | AVG / AVF |
| Virtual MAC | 0000.0c07.acxx (v1) | 0000.5e00.01xx | 0007.b400.xxyy |
| Multicast | 224.0.0.2 (v1) / 224.0.0.102 (v2) | 224.0.0.18 | 224.0.0.102 |
| Default priority | 100 | 100 | 100 |
| Preempt default | Disabled | Enabled | Enabled |
| Load balancing | Per group only | Per group only | Native — multiple forwarders |
! HSRP v2 with interface tracking — decrement priority if the uplink fails R1(config)# interface GigabitEthernet0/0 R1(config-if)# ip address 192.168.10.2 255.255.255.0 R1(config-if)# standby version 2 R1(config-if)# standby 10 ip 192.168.10.1 R1(config-if)# standby 10 priority 110 R1(config-if)# standby 10 preempt R1(config-if)# standby 10 track 1 decrement 20 R1(config)# track 1 interface GigabitEthernet0/1 line-protocol ! VRRP equivalent R1(config-if)# vrrp 10 ip 192.168.10.1 R1(config-if)# vrrp 10 priority 110 R1# show standby brief R1# show vrrp brief R1# show track 1
HSRP preemption is off by default, so a recovered higher-priority router stays Standby until the current Active fails. VRRP preempts by default. Tracking without preemption is pointless: the priority drops, but nothing takes over.
Hands-On Labs
Lab 1 — 802.1Q Trunking and LACP EtherChannel
Configure an 802.1Q trunk between SW1 and SW2 carrying VLANs 10, 20, 30 with native VLAN 99.
SW1(config)# vlan 10 SW1(config-vlan)# name USERS SW1(config)# vlan 20 SW1(config-vlan)# name VOICE SW1(config)# vlan 30 SW1(config-vlan)# name MGMT SW1(config)# vlan 99 SW1(config-vlan)# name NATIVE SW1(config)# interface GigabitEthernet0/1 SW1(config-if)# switchport mode trunk SW1(config-if)# switchport trunk encapsulation dot1q SW1(config-if)# switchport trunk native vlan 99 SW1(config-if)# switchport trunk allowed vlan 10,20,30,99 SW1(config-if)# switchport nonegotiate
Bundle Gi0/2 and Gi0/3 into LACP EtherChannel (port-channel 1) on both switches.
SW1(config)# interface range GigabitEthernet0/2 - 3 SW1(config-if-range)# channel-group 1 mode active ! LACP active SW1(config-if-range)# exit SW1(config)# interface port-channel 1 SW1(config-if)# switchport mode trunk SW1(config-if)# switchport trunk allowed vlan 10,20,30,99 ! SW2 — use passive or active (active+passive also forms channel) SW2(config)# interface range GigabitEthernet0/2 - 3 SW2(config-if-range)# channel-group 1 mode passive ! LACP passive
Verify EtherChannel bundle and trunk status.
SW1# show etherchannel summary ! Look for Po1(SU) — S=Layer2, U=in use. Members should show (P)=bundled SW1# show interfaces trunk ! Verify allowed VLANs and native VLAN on both physical and port-channel interfaces SW1# show interfaces port-channel 1
Lab 2 — RSTP and MST Configuration
Enable Rapid PVST+ and set SW1 as root bridge for VLANs 10,20 and SW2 as root for VLANs 30,99.
SW1(config)# spanning-tree mode rapid-pvst SW1(config)# spanning-tree vlan 10,20 priority 4096 ! Root primary SW1(config)# spanning-tree vlan 30,99 priority 8192 ! Root secondary SW2(config)# spanning-tree mode rapid-pvst SW2(config)# spanning-tree vlan 30,99 priority 4096 SW2(config)# spanning-tree vlan 10,20 priority 8192 ! Enable PortFast + BPDU Guard on access ports SW1(config)# interface GigabitEthernet0/10 SW1(config-if)# spanning-tree portfast SW1(config-if)# spanning-tree bpduguard enable
Configure MST with two instances: MSTI 1 for VLANs 10,20 and MSTI 2 for VLANs 30,99.
SW1(config)# spanning-tree mode mst SW1(config)# spanning-tree mst configuration SW1(config-mst)# name CAMPUS SW1(config-mst)# revision 1 SW1(config-mst)# instance 1 vlan 10,20 SW1(config-mst)# instance 2 vlan 30,99 SW1(config-mst)# exit SW1(config)# spanning-tree mst 1 priority 4096 SW1(config)# spanning-tree mst 2 priority 8192 SW1# show spanning-tree mst SW1# show spanning-tree mst 1 ! View MSTI 1 topology
Lab 3 — OSPF Multi-Area with Summarization
Configure a 3-router OSPF topology: R1 in Area 1, R2 as ABR (Area 0+1), R3 in Area 0.
R1(config)# router ospf 1 R1(config-router)# router-id 1.1.1.1 R1(config-router)# network 10.1.1.0 0.0.0.255 area 1 R1(config-router)# network 10.1.2.0 0.0.0.255 area 1 R1(config-router)# passive-interface GigabitEthernet0/1 ! LAN-facing R2(config)# router ospf 1 R2(config-router)# router-id 2.2.2.2 R2(config-router)# network 10.1.0.0 0.0.255.255 area 1 R2(config-router)# network 10.0.0.0 0.0.0.255 area 0 R2(config-router)# area 1 range 10.1.0.0 255.255.0.0 ! Summarize Area 1 routes
Verify OSPF adjacencies, LSDB, and routing table.
R2# show ip ospf neighbor R2# show ip ospf database ! View all LSA types R2# show ip ospf database summary ! Type 3 LSAs generated by this ABR R3# show ip route ospf ! R3 should see 10.1.0.0/16 summary (not individual /24s) — summarization working
Lab 4 — eBGP Peering and Verification
Configure eBGP between R1 (AS 65001) and R2 (AS 65002) on directly connected interfaces.
R1(config)# router bgp 65001 R1(config-router)# bgp router-id 1.1.1.1 R1(config-router)# neighbor 10.0.0.2 remote-as 65002 R1(config-router)# network 192.168.1.0 mask 255.255.255.0 ! Advertise prefix R2(config)# router bgp 65002 R2(config-router)# bgp router-id 2.2.2.2 R2(config-router)# neighbor 10.0.0.1 remote-as 65001 R2(config-router)# network 172.16.0.0 mask 255.255.0.0
Verify BGP peering state and prefixes.
R1# show bgp summary ! State/PfxRcd — should show integer (# of prefixes), not "Active/Idle" R1# show bgp ipv4 unicast neighbors 10.0.0.2 R1# show bgp ipv4 unicast ! Full BGP table — > = best path R1# show ip route bgp ! BGP routes in RIB (B = BGP, AD 20 for eBGP)
Lab 5 — NAT Overload (PAT) + NTP
Configure PAT so all hosts on 192.168.1.0/24 share a single public IP (203.0.113.1) for internet access.
R1(config)# ip access-list standard NAT_INSIDE R1(config-std-nacl)# permit 192.168.1.0 0.0.0.255 R1(config)# ip nat inside source list NAT_INSIDE interface GigabitEthernet0/1 overload R1(config)# interface GigabitEthernet0/0 R1(config-if)# ip nat inside R1(config)# interface GigabitEthernet0/1 R1(config-if)# ip nat outside
Configure NTP — R1 syncs to upstream server, distributes time to downstream routers.
R1(config)# ntp server 216.239.35.0 prefer ! Upstream NTP R1(config)# ntp authenticate R1(config)# ntp authentication-key 1 md5 Cisco123 R1(config)# ntp trusted-key 1 R2(config)# ntp server 10.0.0.1 ! Sync from R1 R2(config)# ntp authentication-key 1 md5 Cisco123 R2(config)# ntp trusted-key 1 R2(config)# ntp authenticate R1# show ntp status R1# show ntp associations R1# show ip nat translations R1# show ip nat statistics
Lab 6 — PIM-SM Multicast Configuration
Enable IP multicast routing and configure PIM Sparse Mode on all routers. Designate R2 as the RP for 239.0.0.0/8.
R1(config)# ip multicast-routing R1(config)# interface GigabitEthernet0/0 R1(config-if)# ip pim sparse-mode R1(config)# interface GigabitEthernet0/1 R1(config-if)# ip pim sparse-mode R2(config)# ip multicast-routing R2(config)# ip pim rp-address 10.2.2.2 ! R2 is static RP R2(config)# interface GigabitEthernet0/0 R2(config-if)# ip pim sparse-mode ! Configure Auto-RP alternative (R2 = Candidate-RP + Mapping Agent) R2(config)# ip pim send-rp-announce Loopback0 scope 16 R2(config)# ip pim send-rp-discovery Loopback0 scope 16
Verify multicast routing, RP mapping, and PIM neighbors.
R1# show ip pim neighbor R1# show ip pim rp mapping ! Verify RP = 10.2.2.2 for 239.0.0.0/8 R1# show ip mroute ! Multicast routing table: (S,G) and (*,G) entries R1# show ip igmp groups ! IGMP group membership on local segment R1# show ip rpf 10.1.1.10 ! Verify RPF interface for source
Check Your Understanding
Twenty questions on this section. Each answer is explained as you go.
