6.3.7 Packet Tracer - Configure OSPF Authentication Answers

R1(config)# router ospf 1

R1(config-router)# area 0 authentication message-digest

R2(config)# router ospf 1

R2(config-router)# area 0 authentication message-digest

R3(config)# router ospf 1

R3(config-router)# area 0 authentication message-digest

R1(config)# interface g0/0/0

R1(config-if)# ip ospf message-digest-key 1 md5 MD5pa55

R2(config)# interface g0/0/0

R2(config-if)# ip ospf message-digest-key 1 md5 MD5pa55

R2(config-if)# interface g0/0/1

R2(config-if)# ip ospf message-digest-key 1 md5 MD5pa55

R3(config)# interface g0/0/1

R3(config-if)# ip ospf message-digest-key 1 md5 MD5pa55

! ==============================================================
!--- 6.3.7 Packet Tracer - Configure OSPF Authentication
!--- ANSWER SCRIPT FOR ROUTER R1
!--- Usage: copy this whole file and paste it into the R1 terminal (start at the R1> prompt). Every line beginning with "!" is a comment; IOS ignores it, so pasting a comment by accident is harmless.
! ==============================================================

enable
configure terminal

! --------------------------------------------------------------
!--- Part 1: Configure the OSPF MD5 Key on WAN Interfaces.
! --------------------------------------------------------------

!--- Configure the MD5 key on the link to R2 (10.1.1.0/30) so hellos on this segment can be authenticated. Use password MD5pa55 for key 1.
interface gigabitethernet 0/0/0
 ip ospf message-digest-key 1 md5 MD5pa55
 exit

! --------------------------------------------------------------
!--- Part 2: Enable OSPF Area 0 MD5 Authentication.
! --------------------------------------------------------------

!--- Turn on MD5 authentication for every OSPF interface in area 0.
router ospf 1
 area 0 authentication message-digest
 exit

end

! --------------------------------------------------------------
!--- Save the configuration to NVRAM. (Press Enter when prompted for the destination filename.)
! --------------------------------------------------------------
copy running-config startup-config


! ==============================================================
!--- Verification:
!---   show ip ospf interface g0/0/0  -> confirms "Message digest authentication enabled", Youngest key id 1
!---   show ip ospf neighbor          -> confirms the adjacency with R2 stays FULL after authentication is enabled
!---   ping 10.1.1.2                  -> confirms Layer 3 reachability to R2 (OSPF auth doesn't affect plain IP)
!---   ping 192.168.3.5               -> confirms end-to-end reachability to PC-C, proving routes learned via the now-authenticated OSPF session are still valid
!--- Note: G0/0/1 (the LAN side, facing S1) is deliberately left without a message-digest-key. "area 0
!--- authentication message-digest" applies to the whole area, but only interfaces with an active OSPF
!--- neighbor need a matching key to form an adjacency — no other router sits on the 192.168.1.0/24 segment.
! ==============================================================

! ==============================================================
!--- 6.3.7 Packet Tracer - Configure OSPF Authentication
!--- ANSWER SCRIPT FOR ROUTER R2
!--- Usage: copy this whole file and paste it into the R2 terminal (start at the R2> prompt). Every line beginning with "!" is a comment; IOS ignores it, so pasting a comment by accident is harmless.
! ==============================================================

enable
configure terminal

! --------------------------------------------------------------
!--- Part 1: Configure the OSPF MD5 Key on WAN Interfaces.
! --------------------------------------------------------------

!--- Configure the MD5 key on the link to R1 (10.1.1.0/30). Use password MD5pa55 for key 1.
interface gigabitethernet 0/0/0
 ip ospf message-digest-key 1 md5 MD5pa55
 exit

!--- Configure the MD5 key on the link to R3 (10.2.2.0/30). Use password MD5pa55 for key 1.
interface gigabitethernet 0/0/1
 ip ospf message-digest-key 1 md5 MD5pa55
 exit

! --------------------------------------------------------------
!--- Part 2: Enable OSPF Area 0 MD5 Authentication.
! --------------------------------------------------------------

!--- Turn on MD5 authentication for every OSPF interface in area 0.
router ospf 1
 area 0 authentication message-digest
 exit

end

! --------------------------------------------------------------
!--- Save the configuration to NVRAM. (Press Enter when prompted for the destination filename.)
! --------------------------------------------------------------
copy running-config startup-config


! ==============================================================
!--- Verification:
!---   show ip ospf interface brief   -> confirms both G0/0/0 and G0/0/1 show OSPF running with message-digest auth
!---   show ip ospf neighbor          -> confirms adjacencies with both R1 and R3 stay FULL after authentication is enabled
!---   ping 10.1.1.1                  -> confirms Layer 3 reachability to R1
!---   ping 10.2.2.1                  -> confirms Layer 3 reachability to R3
!--- Note: R2 has no directly attached LAN in this topology, so both of its GigabitEthernet interfaces
!--- sit on router-to-router links and both need the message-digest-key — unlike R1/R3, which each have
!--- one WAN interface (keyed) and one LAN interface (not keyed, no OSPF neighbor there).
! ==============================================================

! ==============================================================
!--- 6.3.7 Packet Tracer - Configure OSPF Authentication
!--- ANSWER SCRIPT FOR ROUTER R3
!--- Usage: copy this whole file and paste it into the R3 terminal (start at the R3> prompt). Every line beginning with "!" is a comment; IOS ignores it, so pasting a comment by accident is harmless.
! ==============================================================

enable
configure terminal

! --------------------------------------------------------------
!--- Part 1: Configure the OSPF MD5 Key on WAN Interfaces.
! --------------------------------------------------------------

!--- Configure the MD5 key on the link to R2 (10.2.2.0/30) so hellos on this segment can be authenticated. Use password MD5pa55 for key 1.
interface gigabitethernet 0/0/0
 ip ospf message-digest-key 1 md5 MD5pa55
 exit

! --------------------------------------------------------------
!--- Part 2: Enable OSPF Area 0 MD5 Authentication.
! --------------------------------------------------------------

!--- Turn on MD5 authentication for every OSPF interface in area 0.
router ospf 1
 area 0 authentication message-digest
 exit

end

! --------------------------------------------------------------
!--- Save the configuration to NVRAM. (Press Enter when prompted for the destination filename.)
! --------------------------------------------------------------
copy running-config startup-config


! ==============================================================
!--- Verification:
!---   show ip ospf interface g0/0/0  -> confirms "Message digest authentication enabled", key id 1
!---   show ip ospf neighbor          -> confirms the adjacency with R2 stays FULL after authentication is enabled
!---   ping 10.2.2.2                  -> confirms Layer 3 reachability to R2
!---   ping 192.168.1.5               -> confirms end-to-end reachability to PC-A, proving routes learned via the now-authenticated OSPF session are still valid
!--- Note: G0/0/1 (the LAN side, facing S3) is deliberately left without a message-digest-key, for the
!--- same reason as R1's LAN interface — no other router sits on the 192.168.3.0/24 segment.
! ==============================================================