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Static and Dynamic Routing

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Configure OSPF

  1. Configure OSPF on R1 (LAN-facing interfaces) and all Core and Distribution switches (all Layer-3 interfaces).
    a. Use process ID 1 and Area 0.
    b. Manually configure each device’s RID to match the loopback interface IP.
    c. On switches, use the network command to match the exact IP address of each interface.
    d. On R1, enable OSPF in interface config mode.
    e. Make sure OSPF is enabled on all loopback interfaces, too. Loopback interfaces should be passive.
    f. Each Distribution switch’s SVIs (except the Management VLAN SVI) should be passive, too.
    g. Configure all physical connections between OSPF neighbors to use a network type that doesn’t elect a DR/BDR. (This means point-to-point). NOTE: This doesn’t work on the Layer-3 PortChannel interfaces between CSW1/CSW2. Leave them as the default network type.

For R1, note that even though a sh ip ospf shows that the router-id is the loopback address, the instructions say to manually define it. Configure R1 as defined:

R1#conf t
R1(config)#router ospf 1
R1(config-router)#do sh ip ospf
 Routing Process "ospf 1" with ID 10.0.0.76
 Supports only single TOS(TOS0) routes
 Supports opaque LSA
 SPF schedule delay 5 secs, Hold time between two SPFs 10 secs
 Minimum LSA interval 5 secs. Minimum LSA arrival 1 secs
 Number of external LSA 0. Checksum Sum 0x000000
 Number of opaque AS LSA 0. Checksum Sum 0x000000
 Number of DCbitless external and opaque AS LSA 0
 Number of DoNotAge external and opaque AS LSA 0
 Number of areas in this router is 0. 0 normal 0 stub 0 nssa
 External flood list length 0
R1(config-router)#router-id 10.0.0.76
R1(config-router)#passive-interface l0
R1(config-router)#int l0
R1(config-if)#ip ospf 1 area 0
R1(config-if)#int range g0/0-1
R1(config-if-range)#ip ospf 1 area 0
R1(config-if-range)#ip ospf network point-to-point

Configure CSW1:

CSW1#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
CSW1(config)#router ospf 1

Configure the router-id with the IP address of its loopback interface:

CSW1(config-router)#router-id 10.0.0.77

Make the loopback interface passive:

CSW1(config-router)#passive-interface l0

For the switches, look at the interfaces that have IP addresses:

CSW1(config-router)#do sh ip int br | exclude un
Interface              IP-Address      OK? Method Status                Protocol 
Port-channel1          10.0.0.41       YES manual up                    up 
GigabitEthernet1/0/1   10.0.0.34       YES manual up                    up 
GigabitEthernet1/1/1   10.0.0.45       YES manual up                    up 
GigabitEthernet1/1/2   10.0.0.49       YES manual up                    up 
GigabitEthernet1/1/3   10.0.0.53       YES manual up                    up 
GigabitEthernet1/1/4   10.0.0.57       YES manual up                    up 
Loopback0              10.0.0.77       YES manual up                    up

Activate OSPF on CSWs interfaces:

CSW1(config-router)#network 10.0.0.41 0.0.0.0 area 0
CSW1(config-router)#network 10.0.0.34 0.0.0.0 area 0
CSW1(config-router)#network 10.0.0.45 0.0.0.0 area 0
CSW1(config-router)#network 10.0.0.49 0.0.0.0 area 0
CSW1(config-router)#network 10.0.0.53 0.0.0.0 area 0
CSW1(config-router)#network 10.0.0.57 0.0.0.0 area 0
CSW1(config-router)#network 10.0.0.77 0.0.0.0 area 0

Configure the OSPF type as point-to-point on the switches physical interfaces:

CSW1(config-router)#int range g1/0/1,g1/1/1-4
CSW1(config-if-range)#ip ospf network point-to-point

Configure CSW2:

router ospf 1
router-id 10.0.0.78
network 10.0.0.42 0.0.0.0 area 0
network 10.0.0.38 0.0.0.0 area 0
network 10.0.0.61 0.0.0.0 area 0
network 10.0.0.65 0.0.0.0 area 0
network 10.0.0.69 0.0.0.0 area 0
network 10.0.0.73 0.0.0.0 area 0
network 10.0.0.78 0.0.0.0 area 0
interface range g1/0/1,g1/1/1-4
ip ospf network point-to-point

Then the distribution switches:

DSW-A1:

router ospf 1
router-id 10.0.0.79
passive-interface loopback0
passive-interface vlan 10
passive-interface vlan 20
passive-interface vlan 40
network 10.0.0.46 0.0.0.0 area 0
network 10.0.0.62 0.0.0.0 area 0
network 10.0.0.79 0.0.0.0 area 0
network 10.1.0.2 0.0.0.0 area 0
network 10.2.0.2 0.0.0.0 area 0
network 10.0.0.2 0.0.0.0 area 0
network 10.6.0.2 0.0.0.0 area 0
interface range g1/1/1-2
ip ospf network point-to-point

DSW-A2:

router ospf 1
router-id 10.0.0.80
passive-interface loopback0
passive-interface vlan 10
passive-interface vlan 20
passive-interface vlan 40
network 10.0.0.50 0.0.0.0 area 0
network 10.0.0.66 0.0.0.0 area 0
network 10.0.0.80 0.0.0.0 area 0
network 10.1.0.3 0.0.0.0 area 0
network 10.2.0.3 0.0.0.0 area 0
network 10.0.0.3 0.0.0.0 area 0
network 10.6.0.3 0.0.0.0 area 0
interface range g1/1/1-2
ip ospf network point-to-point

Check the OSPF Neighbors:

Neighbor ID     Pri   State           Dead Time   Address         Interface
10.0.0.79         1   FULL/DR         00:00:33    10.0.0.2        Vlan99
10.0.0.78         0   FULL/  -        00:00:38    10.0.0.65       GigabitEthernet1/1/2
10.0.0.77         0   FULL/  -        00:00:36    10.0.0.49       GigabitEthernet1/1/1

Notice that the interface is VLAN 99.
If we didn’t make the VLAN 10, 20 and 40 SVIs passive, DSW-A1 and A2 would become OSPF neighbors with each other four times – once for each SVI – that isn’t necessary.
Also notice that because we made G1/1/1 and 1/1/2 point-to-point, no DR or BDR are elected for the connections with CSW1 and CSW2: 10.0.0.77 and 78 here.

Configure DSW-B1:

router ospf 1
router-id 10.0.0.81
passive-interface loopback0
passive-interface vlan 10
passive-interface vlan 20
passive-interface vlan 30
network 10.0.0.54 0.0.0.0 area 0
network 10.0.0.70 0.0.0.0 area 0
network 10.0.0.81 0.0.0.0 area 0
network 10.3.0.2 0.0.0.0 area 0
network 10.4.0.2 0.0.0.0 area 0
network 10.5.0.2 0.0.0.0 area 0
network 10.0.0.18 0.0.0.0 area 0
interface range g1/1/1-2
ip ospf network point-to-point

Configure DSW-B2:

router ospf 1
router-id 10.0.0.82
passive-interface loopback0
passive-interface vlan 10
passive-interface vlan 20
passive-interface vlan 30
network 10.0.0.58 0.0.0.0 area 0
network 10.0.0.74 0.0.0.0 area 0
network 10.0.0.82 0.0.0.0 area 0
network 10.3.0.3 0.0.0.0 area 0
network 10.4.0.3 0.0.0.0 area 0
network 10.5.0.3 0.0.0.0 area 0
network 10.0.0.19 0.0.0.0 area 0
interface range g1/1/1-2
ip ospf network point-to-point
  1. Configure one static default route for each of R1’s Internet connections. They should be recursive routes. (meaning they should specify a next hop IP address, but not an exit interface. For review, recursive routes specify only the next hop IP. Directly connected routes specify only the exit interface, and fully specified routes specify both.)

Configure a floating static route

a. Make the route via G0/1/0 a floating static route by configuring an AD value 1 greater than the default.

R1 has two Internet interfaces, G0/0/0 and G0/1/0:

R1#show ip int br
Interface              IP-Address      OK? Method Status                Protocol 
GigabitEthernet0/0     10.0.0.33       YES manual up                    up 
GigabitEthernet0/1     10.0.0.37       YES manual up                    up 
GigabitEthernet0/2     unassigned      YES unset  administratively down down 
GigabitEthernet0/0/0   203.0.113.2     YES DHCP   up                    up 
GigabitEthernet0/1/0   203.0.113.6     YES DHCP   up                    up 
Loopback0              10.0.0.76       YES manual up                    up 
Vlan1                  unassigned      YES unset  administratively down down

They have a /30 prefix length:

R1#show ip int g0/0/0
GigabitEthernet0/0/0 is up, line protocol is up (connected)
  Internet address is 203.0.113.2/30

A /30 subnet only has two usable addresses, .1 and .2 in this case, so that means the ISP’s IP address must be 203.0.113.1. This will be the next hop IP address.

Configure the default route, and the floating static route with a higher AD (than the default of 1 for a static route) for the second WAN interface:

R1(config)#ip route 0.0.0.0 0.0.0.0 203.0.113.1
R1(config)#ip route 0.0.0.0 0.0.0.0 203.0.113.5 ?
  <1-255>  Distance metric for this route
  <cr>
R1(config)#ip route 0.0.0.0 0.0.0.0 203.0.113.5 2

Confirm the primary static route is in the route table:

R1(config)#do sh 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 203.0.113.1 to network 0.0.0.0
xxx
O       10.6.0.0/24 [110/3] via 10.0.0.34, 00:15:14, GigabitEthernet0/0
                    [110/3] via 10.0.0.38, 00:15:14, GigabitEthernet0/1
     203.0.113.0/24 is variably subnetted, 4 subnets, 2 masks
C       203.0.113.0/30 is directly connected, GigabitEthernet0/0/0
L       203.0.113.2/32 is directly connected, GigabitEthernet0/0/0
C       203.0.113.4/30 is directly connected, GigabitEthernet0/1/0
L       203.0.113.6/32 is directly connected, GigabitEthernet0/1/0
S*   0.0.0.0/0 [1/0] via 203.0.113.1

b. R1 should function as an OSPF ASBR, advertising its default route to other routers in the OSPF domain. 

R1#conf t
R1(config)#router ospf 1
R1(config-router)#default-information originate

Confirm propagation at any of the later 3 switches:


DSW-B2(config-if-range)#do show ip route
Codes: C - connected, S - static, I - IGRP, 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 10.0.0.57 to network 0.0.0.0
XXX
O*E2 0.0.0.0/0 [110/1] via 10.0.0.57, 00:00:34, GigabitEthernet1/1/1
               [110/1] via 10.0.0.73, 00:00:34, GigabitEthernet1/1/2

The default route is at the bottom of the routing table. Notice it has two routes installed: one with CSW1 as the next hop, and one with CSW2 as the next hop. If you ping R1’s internet IP from this switch, it should work.

DSW-B2(config-if-range)# do ping 203.0.113.2

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 203.0.113.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 0/0/0 ms

Now try to ping the ISPs IP address:

DSW-B2(config-if-range)#do ping 203.0.113.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 203.0.113.1, timeout is 2 seconds:
UUUUU
Success rate is 0 percent (0/5)

You get 5 U's for unreachable. This is because DSW-B2 is pinging from a private IP address, which the ISP’s router doesn’t accept. To solve that, we need to configure NAT, network address translation in the next section.