PTL-0029 verification guide

This document details the complete positive and negative testing matrix for PTL-0029, executed and verified inside Cisco Packet Tracer 9.0.1.

1. Positive Verification (POS)#

POS-01: Multi-Access Subnet IP Reachability#

From R1 privileged EXEC mode, verify direct ICMP echo reachability to all other devices sharing the 192.168.1.0/24 multi-access broadcast segment:

R1# ping 192.168.1.2

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 0/0/0 ms

R1# ping 192.168.1.3

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 0/0/0 ms

R1# ping 192.168.1.50

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.50, timeout is 2 seconds:
.!!!!
Success rate is 80 percent (4/5), round-trip min/avg/max = 0/0/0 ms

Criteria: All endpoints on 192.168.1.0/24 respond with 100% (or 80% on initial ARP) success.

POS-02: Multi-Access OSPF Neighbor Adjacency Inspection#

Verify the neighbor relationship tables on each router:

On R1:

R1# show ip ospf neighbor

Neighbor ID     Pri   State           Dead Time   Address         Interface
3.3.3.3           0   FULL/DROTHER    00:00:36    192.168.1.3     GigabitEthernet0/0/0
2.2.2.2         100   FULL/BDR        00:00:30    192.168.1.2     GigabitEthernet0/0/0

On R2:

R2# show ip ospf neighbor

Neighbor ID     Pri   State           Dead Time   Address         Interface
3.3.3.3           0   FULL/DROTHER    00:00:33    192.168.1.3     GigabitEthernet0/0/0
1.1.1.1         255   FULL/DR         00:00:31    192.168.1.1     GigabitEthernet0/0/0

On R3:

R3# show ip ospf neighbor

Neighbor ID     Pri   State           Dead Time   Address         Interface
2.2.2.2         100   FULL/BDR        00:00:34    192.168.1.2     GigabitEthernet0/0/0
1.1.1.1         255   FULL/DR         00:00:38    192.168.1.1     GigabitEthernet0/0/0

Criteria: R1 sees R2 as FULL/BDR and R3 as FULL/DROTHER. R2 sees R1 as FULL/DR and R3 as FULL/DROTHER. R3 sees R1 as FULL/DR and R2 as FULL/BDR.

POS-03: Detailed OSPF Interface Role and Priority Validation#

Inspect interface-level OSPF state on GigabitEthernet0/0/0 across each router:

On R1 (DR):

R1# show ip ospf interface GigabitEthernet0/0/0

GigabitEthernet0/0/0 is up, line protocol is up
  Internet address is 192.168.1.1/24, Area 0
  Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 1
  Transmit Delay is 1 sec, State DR, Priority 255
  Designated Router (ID) 1.1.1.1, Interface address 192.168.1.1
  Backup Designated Router (ID) 2.2.2.2, Interface address 192.168.1.2
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5

On R2 (BDR):

R2# show ip ospf interface GigabitEthernet0/0/0

GigabitEthernet0/0/0 is up, line protocol is up
  Internet address is 192.168.1.2/24, Area 0
  Process ID 1, Router ID 2.2.2.2, Network Type BROADCAST, Cost: 1
  Transmit Delay is 1 sec, State BDR, Priority 100
  Designated Router (ID) 1.1.1.1, Interface address 192.168.1.1
  Backup Designated Router (ID) 2.2.2.2, Interface address 192.168.1.2
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5

On R3 (DROTHER):

R3# show ip ospf interface GigabitEthernet0/0/0

GigabitEthernet0/0/0 is up, line protocol is up
  Internet address is 192.168.1.3/24, Area 0
  Process ID 1, Router ID 3.3.3.3, Network Type BROADCAST, Cost: 1
  Transmit Delay is 1 sec, State DROTHER, Priority 0
  Designated Router (ID) 1.1.1.1, Interface address 192.168.1.1
  Backup Designated Router (ID) 2.2.2.2, Interface address 192.168.1.2
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5

Criteria: State matches DR for R1 (Priority 255), BDR for R2 (Priority 100), and DROTHER for R3 (Priority 0).

POS-04: OSPF Route Installation and Data Plane Reachability#

Verify that loopback networks are learned via OSPF on R3:

R3# show ip route ospf
     10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
O       10.1.1.1 [110/2] via 192.168.1.1, 00:05:12, GigabitEthernet0/0/0
O       10.2.2.1 [110/2] via 192.168.1.2, 00:05:12, GigabitEthernet0/0/0

Verify end-to-end ping reachability from PC-1:

C:\> ping 10.1.1.1
Reply from 10.1.1.1: bytes=32 time=16ms TTL=255
Reply from 10.1.1.1: bytes=32 time<1ms TTL=255

C:\> ping 10.2.2.1
Reply from 10.2.2.1: bytes=32 time=1ms TTL=255

C:\> ping 10.3.3.1
Reply from 10.3.3.1: bytes=32 time=1ms TTL=255

Criteria: All advertised subnets (10.1.1.1, 10.2.2.1, 10.3.3.1) are present in routing tables and reachable via ICMP echo.

2. Negative Verification (NEG)#

NEG-01: DR Failover and DROTHER Exclusion#

When R1's multi-access interface is administratively disabled (shutdown), R2 promotes from BDR to DR. Because R3 has priority 0, it must remain DROTHER and never be promoted to BDR:

On R2:

R2# show ip ospf interface GigabitEthernet0/0/0
GigabitEthernet0/0/0 is up, line protocol is up
  Internet address is 192.168.1.2/24, Area 0
  Process ID 1, Router ID 2.2.2.2, Network Type BROADCAST, Cost: 1
  Transmit Delay is 1 sec, State DR, Priority 100
  Designated Router (ID) 2.2.2.2, Interface address 192.168.1.2
  No backup designated router on this network

On R3:

R3# show ip ospf interface GigabitEthernet0/0/0
GigabitEthernet0/0/0 is up, line protocol is up
  Internet address is 192.168.1.3/24, Area 0
  Process ID 1, Router ID 3.3.3.3, Network Type BROADCAST, Cost: 1
  Transmit Delay is 1 sec, State DROTHER, Priority 0
  Designated Router (ID) 2.2.2.2, Interface address 192.168.1.2
  No backup designated router on this network

Criteria: R2 is promoted to DR. R3 remains DROTHER. The segment indicates No backup designated router on this network because no eligible routers remain.

NEG-02: Non-Preemptive OSPF Election Behavior#

When R1's interface is restored (no shutdown), OSPF does not preempt the active DR (R2). R1 assumes the open BDR role rather than usurping the DR role, despite its higher priority (255 vs 100). Only upon a manual process reset (clear ip ospf process) does R1 resume the DR role:

R1# show ip ospf interface GigabitEthernet0/0/0
GigabitEthernet0/0/0 is up, line protocol is up
  Internet address is 192.168.1.1/24, Area 0
  Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 1
  Transmit Delay is 1 sec, State DR, Priority 255
  Designated Router (ID) 1.1.1.1, Interface address 192.168.1.1
  Backup Designated Router (ID) 2.2.2.2, Interface address 192.168.1.2

Criteria: Non-preemption ensures network stability until an intentional topology change or process reset occurs.

Verification Guide: PTL-0029 OSPFv2 DR and BDR Elections