Baseline: Intra-domain routing using default settings

Each of the routing domains in Network for redistribution example is defined with simple VLANs and a basic routing configuration:

  • In the RIP domains, the RIP protocol is assigned to each VLAN that a router connects to.

  • Routers in the RIP domains redistribute connected routes—this is the default setting when RIP is enabled.

  • For simplicity, all VLANs in the OSPF domain are assigned to the backbone area (area 0.)

  • Border routers (North and South) implement both RIP and OSPF protocols.

The following listing shows the running configuration for the South router, the most complicated of the routers in this example. (Not only is the South router a border router, but it also has host computers connected directly to it in both RIP and OSPF domains.)

South(config)# show run

Running configuration:

; J8697A Configuration Editor; Created on release
#K.15.01.0031

hostname "South"
module 1 type J8702A
module 3 type J9478A
ip routing
vlan 1
   name "DEFAULT_VLAN"
   untagged A19-A24,C13-C24
   ip address dhcp-bootp
   no untagged A1-A18,C1-C12
   exit
vlan 31
   name "VLAN31"
   untagged A1-A6
   ip address 10.3.31.2 255.255.255.0
   exit
vlan 33
   name "VLAN33"
   untagged A7-A12
   ip address 10.3.33.2 255.255.255.0
   exit
vlan 21
   name "VLAN21"
   untagged A13-A18
   ip address 10.2.21.1 255.255.255.0
   exit
vlan 37
   name "VLAN37"
   untagged C1-C6
   ip address 10.3.37.1 255.255.255.0
   exit
vlan 29
   name "VLAN29"
   untagged C7-C12
   ip address 10.2.29.1 255.255.255.0
   exit
router ospf
   area backbone
   exit
router rip
   redistribute connected
   exit
snmp-server community "public" unrestricted
vlan 21
   ip rip 10.2.21.1
   exit
vlan 29
   ip rip 10.2.29.1
   exit
vlan 31
   ip ospf 10.3.31.2 area backbone
   exit
vlan 33
   ip ospf 10.3.33.2 area backbone
   exit
vlan 37
   ip ospf 10.3.37.1 area backbone
   exit
Items of particular interest are:

  • The ip routing command enables routing on the switch.

  • The router ospf command enables OSPF routing on the switch. The area backbone command establishes the backbone area (area 0.)

  • The router rip command enables RIP routing on the switch. The redistribute connected command redistributes directly connected routes to all routers in the attached RIP domain.

  • The vlan commands at the end of the configuration assign routing protocols to the VLANs. Additionally, they make area assignments for VLANs in the OSPF domain.

The other routers have analogous, if somewhat simpler, routing configurations. The Northwest, Northeast, and Southeast routers have only RIP enabled, and the East router has only OSPF enabled. The North router enables both routing protocols, but has fewer VLANs.

Listed below are the routing tables that result for three representative routers:
South

A border router attached to both RIP and OSPF domains.

East

A router within the OSPF domain.

Southeast

A router within the RIP domain.

 South(config)# show ip route 
 
                               IP Route Entries 

  Destination     Gateway         VLAN Type      Sub-Type   Metric     Dist. 
  --------------- --------------- ---- --------- ---------- ---------- ----- 
  10.2.21.0/24    VLAN21          21   connected            1          0 
  10.2.22.0/24    10.2.21.2       21   rip                  2          120 
  10.2.23.0/24    10.2.21.2       21   rip                  2          120 
  10.2.29.0/24    VLAN29          29   connected            1          0 
  10.3.31.0/24    VLAN31          31   connected            1          0 
  10.3.32.0/24    10.3.31.1       31   ospf      IntraArea  2          110 
  10.3.32.0/24    10.3.33.1       33   ospf      IntraArea  2          110 
  10.3.33.0/24    VLAN33          33   connected            1          0 
  10.3.34.0/24    10.3.33.1       33   ospf      IntraArea  2          110 
  10.3.37.0/24    VLAN37          37   connected            1          0 
  127.0.0.0/8     reject               static               0          0 
  127.0.0.1/32    lo0                  connected            1          0 
  
  
  
 East(config)# show ip route 
 
                             IP Route Entries 

  Destination     Gateway         VLAN Type      Sub-Type   Metric     Dist. 
  --------------- --------------- ---- --------- ---------- ---------- ----- 
  10.3.31.0/24    10.3.32.1       32   ospf      IntraArea  2          110 
  10.3.31.0/24    10.3.33.2       33   ospf      IntraArea  2          110 
  10.3.32.0/24    VLAN32          32   connected            1          0 
  10.3.33.0/24    VLAN33          33   connected            1          0 
  10.3.34.0/24    VLAN34          34   connected            1          0 
  10.3.37.0/24    10.3.33.2       33   ospf      IntraArea  2          110 
  127.0.0.0/8     reject               static               0          0 
  127.0.0.1/32    lo0                  connected            1          0 
 
 

Southeast(config)# show ip route 

                            IP Route Entries 

  Destination     Gateway         VLAN Type      Sub-Type   Metric     Dist. 
  --------------- --------------- ---- --------- ---------- ---------- ----- 
  10.2.21.0/24    VLAN21          21   connected            1          0 
  10.2.22.0/24    VLAN22          22   connected            1          0 
  10.2.23.0/24    VLAN23          23   connected            1          0 
  10.2.29.0/24    10.2.21.1       21   rip                  2          120 
  10.3.31.0/24    10.2.21.1       21   rip                  2          120 
  10.3.33.0/24    10.2.21.1       21   rip                  2          120 
  10.3.37.0/24    10.2.21.1       21   rip                  2          120 
  127.0.0.0/8     reject               static               0          0 
  127.0.0.1/32    lo0                  connected            1          0

With this configuration, the routers and host computers in each routing domain are able to communicate with all other routers and hosts in that domain. In addition, the routers and hosts in the RIP domains can communicate with all interfaces of the adjacent border router and with hosts attached to those interfaces. (To prevent that cross-domain communication, you would remove the redistribute connected command from the router rip context.) Beyond those connected routes on the RIP side, there is no inter-domain communication.

Thus, host Z can ping host X and host L, but not host M or host B. And host M can ping host L, but not host X or host Y or host A. And so on.