16.3.1 Packet Tracer – Troubleshoot Static and Default Routes

16.3.1 Packet Tracer - Troubleshoot Static and Default Routes (Instructor Version)

Addressing Table

Device	Interface	IP Addresses
R1	G0/0	172.31.1.1/25
	G0/0	2001:DB8:1::1/64
	S0/0/0	172.31.1.194/30
	S0/0/0	2001:DB8:2::194/64
R2	G0/0	172.31.0.1/24
	G0/0	2001:DB8:3::1/64
	S0/0/0	172.31.1.193/30
	S0/0/0	2001:DB8:2::193/64
	S0/0/1	172.31.1.197/30
	S0/0/1	2001:DB8:4::197/64
R3	G0/0	172.31.1.129/26
	G0/0	2001:DB8:5::1/64
	S0/0/1	172.31.1.198/30
	S0/0/1	2001:DB8:4::198/64
PC1	NIC	172.31.1.126/25
PC1	NIC	2001:DB8:1::126/64
PC2	NIC	172.31.0.254/24
PC2	NIC	2001:DB8:3::254/64
Server	NIC	172.31.1.190/26
Server	NIC	2001:DB8:5::190/64

Objectives

In this activity you will troubleshoot static and default routes and repair any errors that you find.

Troubleshoot IPv4 static routes.
Troubleshoot IPv4 default routes.
Troubleshoot IPv6 static routes.
Configure IPv4 static routes.
Configure IPv4 default routes.
Configure IPv6 static routes.

Background / Scenario

A newly hired network technician is attempting to preconfigure a simple topology that will be delivered to a customer. The technician has not been able to establish connectivity between the three LANs. You have been asked to troubleshoot the topology and verify connectivity between the hosts on the three LANs over IPv4 and IPv6.

Instructions

Step 1: Locate and document the problems.

Review the routing table on R1, R2, R3.

R1#show ip route 
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
       i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
       * - candidate default, U - per-user static route, o - ODR
       P - periodic downloaded static route

Gateway of last resort is 172.31.1.195 to network 0.0.0.0

     172.31.0.0/16 is variably subnetted, 4 subnets, 3 masks
C       172.31.1.0/25 is directly connected, GigabitEthernet0/0
L       172.31.1.1/32 is directly connected, GigabitEthernet0/0
C       172.31.1.192/30 is directly connected, Serial0/0/0
L       172.31.1.194/32 is directly connected, Serial0/0/0
S*   0.0.0.0/0 [1/0] via 172.31.1.195

R1#
R1#show ipv6 route 
IPv6 Routing Table - 8 entries
Codes: C - Connected, L - Local, S - Static, R - RIP, B - BGP
       U - Per-user Static route, M - MIPv6
       I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea, IS - ISIS summary
       ND - ND Default, NDp - ND Prefix, DCE - Destination, NDr - Redirect
       O - OSPF intra, OI - OSPF inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
       ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2
       D - EIGRP, EX - EIGRP external
C   2001:DB8:1::/64 [0/0]
     via GigabitEthernet0/0, directly connected
L   2001:DB8:1::1/128 [0/0]
     via GigabitEthernet0/0, receive
C   2001:DB8:2::/64 [0/0]
     via Serial0/0/0, directly connected
L   2001:DB8:2::194/128 [0/0]
     via Serial0/0/0, receive
S   2001:DB8:3::/64 [1/0]
     via Serial0/0/0, directly connected
S   2001:DB8:4::/64 [1/0]
     via Serial0/0/0, directly connected
S   2001:DB8:5::/64 [1/0]
     via Serial0/0/0, directly connected
L   FF00::/8 [0/0]
     via Null0, receive
R1#

R2#show ip route 
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
       i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
       * - candidate default, U - per-user static route, o - ODR
       P - periodic downloaded static route

Gateway of last resort is not set

     172.31.0.0/16 is variably subnetted, 8 subnets, 5 masks
C       172.31.0.0/24 is directly connected, GigabitEthernet0/0
L       172.31.0.1/32 is directly connected, GigabitEthernet0/0
S       172.31.1.0/25 [1/0] via 172.31.1.198
S       172.31.1.128/26 [1/0] via 172.31.1.194
C       172.31.1.192/30 is directly connected, Serial0/0/0
L       172.31.1.193/32 is directly connected, Serial0/0/0
C       172.31.1.196/30 is directly connected, Serial0/0/1
L       172.31.1.197/32 is directly connected, Serial0/0/1

R2#show ipv6 route 
IPv6 Routing Table - 9 entries
Codes: C - Connected, L - Local, S - Static, R - RIP, B - BGP
       U - Per-user Static route, M - MIPv6
       I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea, IS - ISIS summary
       ND - ND Default, NDp - ND Prefix, DCE - Destination, NDr - Redirect
       O - OSPF intra, OI - OSPF inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
       ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2
       D - EIGRP, EX - EIGRP external
S   2001:DB6:1::/64 [1/0]
     via 2001:DB8:2::194
C   2001:DB8:2::/64 [0/0]
     via Serial0/0/0, directly connected
L   2001:DB8:2::193/128 [0/0]
     via Serial0/0/0, receive
C   2001:DB8:3::/64 [0/0]
     via GigabitEthernet0/0, directly connected
L   2001:DB8:3::1/128 [0/0]
     via GigabitEthernet0/0, receive
C   2001:DB8:4::/64 [0/0]
     via Serial0/0/1, directly connected
L   2001:DB8:4::197/128 [0/0]
     via Serial0/0/1, receive
S   2001:DB8:5::/64 [1/0]
     via 2001:DB8:4::198
L   FF00::/8 [0/0]
     via Null0, receive
R2#

R3#show ip route 
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
       i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
       * - candidate default, U - per-user static route, o - ODR
       P - periodic downloaded static route

Gateway of last resort is not set

     172.31.0.0/16 is variably subnetted, 7 subnets, 5 masks
S       172.31.0.0/24 is directly connected, Serial0/0/1
S       172.31.1.0/28 is directly connected, Serial0/0/1
C       172.31.1.128/26 is directly connected, GigabitEthernet0/0
L       172.31.1.129/32 is directly connected, GigabitEthernet0/0
S       172.31.1.192/30 is directly connected, Serial0/0/1
C       172.31.1.196/30 is directly connected, Serial0/0/1
L       172.31.1.198/32 is directly connected, Serial0/0/1

R3#show ipv6 route 
IPv6 Routing Table - 7 entries
Codes: C - Connected, L - Local, S - Static, R - RIP, B - BGP
       U - Per-user Static route, M - MIPv6
       I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea, IS - ISIS summary
       ND - ND Default, NDp - ND Prefix, DCE - Destination, NDr - Redirect
       O - OSPF intra, OI - OSPF inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
       ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2
       D - EIGRP, EX - EIGRP external
S   2001:DB8:2::/64 [1/0]
     via Serial0/0/1, directly connected
S   2001:DB8:3::/64 [1/0]
     via Serial0/0/1, directly connected
C   2001:DB8:4::/64 [0/0]
     via Serial0/0/1, directly connected
L   2001:DB8:4::198/128 [0/0]
     via Serial0/0/1, receive
C   2001:DB8:5::/64 [0/0]
     via GigabitEthernet0/0, directly connected
L   2001:DB8:5::1/128 [0/0]
     via GigabitEthernet0/0, receive
L   FF00::/8 [0/0]
     via Null0, receive
R3#

Record your findings in a table like the one below.

Location	Problem	Solution
R1	IPv4 Default route next hop interface address is incorrect.	Change next hop address to 172.31.1.193
R2	IPv6 route to LAN 1 has the wrong network address for the destination network.	Change destination address from 2001:DB6:1::/64 to 2001:DB8:1::/64
R2	The next hop addresses in the two IPv4 routes are reversed.	Change the statements to `ip route 172.31.1.0 255.255.255.128 172.31.1.194` and `ip route 172.31.1.128 255.255.255.192 172.31.1.198`
R3	The IPv6 route to LAN 1 is missing.	Configure a directly connected static route to 2001:DB8:1::/64
R3	The IPv4 route to LAN 1 has the wrong mask for the network.	Change the mask to 255.255.255.128

Step 2: Repair the problems.

Configure the devices so that full connectivity exists between the hosts on the LANs over IPv4 and IPv6.

Note: Your task is to establish connectivity using the existing static route design. Changing the types of static routes used will result in a loss of points.

Device Configs - Final

Router R1

! ==============================================================
!--- 16.3.1 Packet Tracer - Troubleshoot Static and Default Routes
!--- FIX SCRIPT FOR ROUTER R1
!--- Usage: from the console on R1, enter privileged EXEC mode with "enable", then paste this whole file. Every line beginning with "!" is a comment; IOS ignores it, so pasting a comment by accident is harmless.
!--- CRITICAL FIX: the source Answer Configuration replaces R1's broken default route with "172.16.1.193" - a completely different network (172.16.x.x) than the one this topology actually uses (172.31.x.x). This is a typo for "172.31.1.193" (R2's S0/0/0 address), matching both the Addressing Table and the Documentation Table's own stated solution. Left as-is, this "fix" would silently fail to restore connectivity while looking configured.
! ==============================================================

enable
configure terminal

! --------------------------------------------------------------
!--- Documentation Table, Location R1: fix the default route's next-hop address
! --------------------------------------------------------------

!--- The existing default route points at 172.31.1.195 (the broadcast address of the 172.31.1.192/30 link, not a usable host address) - remove it and replace it with R2's actual S0/0/0 address.
no ip route 0.0.0.0 0.0.0.0 172.31.1.195
ip route 0.0.0.0 0.0.0.0 172.31.1.193

end

! --------------------------------------------------------------
!--- Operational habit (not explicitly required by this lab): save to NVRAM. (Press Enter when prompted for the destination filename.)
! --------------------------------------------------------------
copy running-config startup-config

! ==============================================================
!--- Verification:
!---   R1# show ip route static -> S* 0.0.0.0/0 [1/0] via 172.31.1.193
!---   From PC1, ping PC2 and the Server (IPv4) -> success once R2 and R3's fixes are also applied
! ==============================================================

Router R2

! ==============================================================
!--- 16.3.1 Packet Tracer - Troubleshoot Static and Default Routes
!--- FIX SCRIPT FOR ROUTER R2
!--- Usage: from the console on R2, enter privileged EXEC mode with "enable", then paste this whole file. Every line beginning with "!" is a comment; IOS ignores it, so pasting a comment by accident is harmless.
!--- CRITICAL FIX: the source Answer Configuration's "no ipv6 route" command targets next-hop "2001:DB8:3::194", but the actual broken route shown in "show ipv6 route" uses next-hop "2001:DB8:2::194" instead. Since "no ipv6 route" must match the existing route's parameters exactly to remove it, the command as originally written would silently fail to remove anything, leaving the broken route (and its wrong destination network, DB6 instead of DB8) still in place. Fixed below.
! ==============================================================

enable
configure terminal

! --------------------------------------------------------------
!--- Documentation Table, Location R2 (1 of 2): fix the reversed IPv4 next-hop addresses to LAN 1 and LAN 3
! --------------------------------------------------------------

!--- These two routes had their next-hops swapped - LAN 1 (172.31.1.0/25) needs to go via R1's S0/0/0 address, and LAN 3 (172.31.1.128/26) needs to go via R3's S0/0/1 address.
no ip route 172.31.1.0 255.255.255.128 172.31.1.198
no ip route 172.31.1.128 255.255.255.192 172.31.1.194
ip route 172.31.1.0 255.255.255.128 172.31.1.194
ip route 172.31.1.128 255.255.255.192 172.31.1.198

! --------------------------------------------------------------
!--- Documentation Table, Location R2 (2 of 2): fix the wrong destination network in the IPv6 route to LAN 1
! --------------------------------------------------------------

!--- The existing route's next-hop (2001:DB8:2::194, R1's actual S0/0/0 IPv6 address) is already correct - only the destination network itself is wrong (DB6 instead of DB8). The "no" command below must match that actual next-hop exactly, or it won't remove anything.
no ipv6 route 2001:DB6:1::/64 2001:DB8:2::194
ipv6 route 2001:DB8:1::/64 2001:DB8:2::194

end

! --------------------------------------------------------------
!--- Operational habit (not explicitly required by this lab): save to NVRAM. (Press Enter when prompted for the destination filename.)
! --------------------------------------------------------------
copy running-config startup-config

! ==============================================================
!--- Verification:
!---   R2# show ip route static   -> 172.31.1.0/25 via 172.31.1.194, 172.31.1.128/26 via 172.31.1.198
!---   R2# show ipv6 route static -> 2001:DB8:1::/64 via 2001:DB8:2::194 (the DB6 route is gone)
!---   From PC2, ping PC1 and the Server (IPv4 and IPv6) -> success once R1 and R3's fixes are also applied
! ==============================================================

Router R3

! ==============================================================
!--- 16.3.1 Packet Tracer - Troubleshoot Static and Default Routes
!--- FIX SCRIPT FOR ROUTER R3
!--- Usage: from the console on R3, enter privileged EXEC mode with "enable", then paste this whole file. Every line beginning with "!" is a comment; IOS ignores it, so pasting a comment by accident is harmless.
!--- The source Answer Configuration for R3 was already correct - no fixes needed here.
! ==============================================================

enable
configure terminal

! --------------------------------------------------------------
!--- Documentation Table, Location R3 (1 of 2): fix the wrong mask on the IPv4 route to LAN 1
! --------------------------------------------------------------

!--- The existing route used a /28 mask (255.255.255.240); LAN 1 is actually a /25 (255.255.255.128) per the Addressing Table.
no ip route 172.31.1.0 255.255.255.240 Serial0/0/1
ip route 172.31.1.0 255.255.255.128 Serial0/0/1

! --------------------------------------------------------------
!--- Documentation Table, Location R3 (2 of 2): add the missing IPv6 route to LAN 1
! --------------------------------------------------------------

!--- "Directly connected" style (exit-interface only), matching the existing static route design already used elsewhere on this router (its other IPv6/IPv4 routes toward R1/R2 use the same style).
ipv6 route 2001:DB8:1::/64 Serial0/0/1

end

! --------------------------------------------------------------
!--- Operational habit (not explicitly required by this lab): save to NVRAM. (Press Enter when prompted for the destination filename.)
! --------------------------------------------------------------
copy running-config startup-config

! ==============================================================
!--- Verification:
!---   R3# show ip route static   -> 172.31.1.0/25 (not /28) via Serial0/0/1
!---   R3# show ipv6 route static -> 2001:DB8:1::/64 now present via Serial0/0/1
!---   From the Server, ping PC1 and PC2 (IPv4 and IPv6) -> success once R1 and R2's fixes are also applied
! ==============================================================

Download Packet Tracer (.pka) file: