Prerequisites: CCNP level skills.
Cisco IOS OSPF modes:
- Point-to-point (Cisco)
- Broadcast (Cisco)
- Non-broadcast (RFC 2328)
- Point-to-multipoint (RFC 2328)
- Point-to-multipoint non-broadcast (Cisco)
Topology
Pic. 1 – Topology Diagram.
Workflow
- Get familiar with the topology.
- Read the ‘Task List‘.
- Read the ‘Questions‘ and provide the answers BEFORE configuring the routers.
- Configure the lab according to the ‘Task List‘ .
- Compare the answers (step 3) with the lab results.
Task List
- Configure IP addresses as per topology diagram and use encapsulation Frame-Relay on S0/0 interfaces.
- Make sure that you use only DLCIs specified in the topology diagram (pic. 1) and routers do not learn any other DLCIs dynamically.
- R2 should use only one layer 3 to layer 2 mapping. Also R3 should use only one layer 3 to layer 2 mapping.
- Configure OSPF with all links in area 0. Make sure that R2 can ping R3‘s loopback0 and S0/0 interfaces (R2 must not have frame-relay mapping to R3).
Questions
- What are the differences betweent OSPF point-to-multipoint and non-broadcast on Frame-Relay links?
- Does point-to-multipoint mode networks use multicast or unicast to transmit OSPF packets? Why?
- What are the default hello/dead interval timers on point-to-multipoint links?
Lab Solution
R1 Configuration:
!
interface loopback0
ip address 172.16.101.1 255.255.255.0
ip ospf network point-to-point
!
ip ospf network point-to-point
!
interface Serial0/0
ip address 10.1.1.1 255.255.255.0
encapsulation frame-relay
ip ospf network point-to-multipoint
frame-relay map ip 10.1.1.2 102 broadcast
frame-relay map ip 10.1.1.3 103 broadcast
no frame-relay inverse-arp
!
ip address 10.1.1.1 255.255.255.0
encapsulation frame-relay
ip ospf network point-to-multipoint
frame-relay map ip 10.1.1.2 102 broadcast
frame-relay map ip 10.1.1.3 103 broadcast
no frame-relay inverse-arp
!
router ospf 1
router-id 1.1.1.1
log-adjacency-changes
network 10.1.1.1 0.0.0.0 area 0
network 172.16.101.1 0.0.0.0 area 0
router-id 1.1.1.1
log-adjacency-changes
network 10.1.1.1 0.0.0.0 area 0
network 172.16.101.1 0.0.0.0 area 0
!
R2 Configuration:
!
interface Loopback0
ip address 172.16.102.2 255.255.255.0
ip ospf network point-to-point
!
ip address 172.16.102.2 255.255.255.0
ip ospf network point-to-point
!
interface Serial0/0
ip address 10.1.1.2 255.255.255.0
encapsulation frame-relay
ip ospf network point-to-multipoint
frame-relay map ip 10.1.1.1 201 broadcast
no frame-relay inverse-arp
!
ip address 10.1.1.2 255.255.255.0
encapsulation frame-relay
ip ospf network point-to-multipoint
frame-relay map ip 10.1.1.1 201 broadcast
no frame-relay inverse-arp
!
router ospf 1
router-id 2.2.2.2
log-adjacency-changes
network 10.1.1.2 0.0.0.0 area 0
network 172.16.102.2 0.0.0.0 area 0
!
router-id 2.2.2.2
log-adjacency-changes
network 10.1.1.2 0.0.0.0 area 0
network 172.16.102.2 0.0.0.0 area 0
!
R3 Configuration:
!
interface Loopback0
ip address 172.16.103.3 255.255.255.0
ip ospf network point-to-point
!
ip address 172.16.103.3 255.255.255.0
ip ospf network point-to-point
!
interface Serial0/0
ip address 10.1.1.3 255.255.255.0
encapsulation frame-relay
ip ospf network point-to-multipoint
frame-relay map ip 10.1.1.1 301 broadcast
no frame-relay inverse-arp
!
ip address 10.1.1.3 255.255.255.0
encapsulation frame-relay
ip ospf network point-to-multipoint
frame-relay map ip 10.1.1.1 301 broadcast
no frame-relay inverse-arp
!
router ospf 1
router-id 3.3.3.3
log-adjacency-changes
network 10.1.1.3 0.0.0.0 area 0
network 172.16.103.3 0.0.0.0 area 0
!
router-id 3.3.3.3
log-adjacency-changes
network 10.1.1.3 0.0.0.0 area 0
network 172.16.103.3 0.0.0.0 area 0
!
Verification
Note!
OSPF point-to-multipoint treats the circuits as point-to-point links so no DR/BDR are elected. In addition to that, the spokes do not have to have IP-to-DLCI mapping via R1. R1 resolves the reachability between spokes by injecting itself as the next-hop. Both spokes know how to reach R1 according to IP-to-DLCI static mapping.
Pic. 2 – Only DLCIs as per Topology Diagram.
Pic. 3 – R1’s Adjacencies with R2 and R3.
Pic. 4 – R2 /32 Route Injected by R1.
Pic. 5 – Traceroute.