The Stub (six) of special OSPF area and OSPF Totally Stub region Detailed configuration and

Foreword

OSPF routers need to maintain intra-domain routing, inter-domain routing, external routing information database. Domain Routing here mainly refers to a class, second class the LSA; interdomain routing the LSA mainly refers to three, mainly refers to external routes four, five the LSA, we are done in the foregoing detailed description.

When the network is expanding, LSDB scale will continue to increase. We have a way

给OSPF划分区域：分为骨干区域和非骨干区域。

OSPF backbone area router general performance would be more powerful, able to carry and maintain more LSDB, but some non-backbone area router may not carry too much LSDB.
Such is indeed divided regions effectively reduce the entry of the LSA, but some non-backbone area router or more will receive three, four, five LSA. ** And we found that some non-backbone area router does not need to provide transit traffic to other regions, the router within the region there is no need to maintain the LSDB outside the region. *** So in order to further reduce the size and number of the router LSDB LSA, we can further reduce the number and size of LSA routing table through a special area of OSFP.

As shown below: AR4 and AR5 region where the flow rate need not be provided for the other transfer region.

Stub area and Totally Stub area

Transmission area networks and terminal

As shown above, the whole network can be divided into four parts Area 0, Area 1, Area 2, the external network. Between the four parts of the main flow as shown in each access red.

OSPF for each area can be divided into two types:

1. Transmission regions: the region in addition to carrying traffic and traffic originating in the region, but also carries a source and destination IP traffic do not belong to the region, i.e., "through type flow", as Area 0.
2. Terminal region: only the traffic of the region access and traffic originating in the region, such as Area 1, Area 2.

For terminal region need to consider several issues:

1. The need to save to reach other areas of specific routes: access other areas through a single outlet (here, RTB, RTC), "summary" Routing relatively more concise and specific routes.
2. Equipment performance: network construction and maintenance cost factors must be considered. Alternatively deployed terminal region of relatively low performance of the router.

OSPF routers to calculate the area, inter-area external routes need to rely on the network to collect a large number of LSA, LSA will take up a lot of storage space LSDB, so the key is to solve the problem without affecting the normal route, reducing the number of the LSA.

Stub Area

At this time, we will be able to configure the terminal region Stub area, to reduce the number of LSA.

The ABR Stub area which does not propagate into the area external route Stub received (corresponding to the four, five the LSA), Stub area routers in the LSDB, routing table size will be greatly reduced.
To ensure Stub area outside the autonomous system to reach, the ABR Stub area will generate a default route (corresponding to the three types of the LSA) , and advertised to other routers Stub region.

Stub area is an optional configuration attribute, but it is not recommended to each zone in the Stub area. Generally speaking, Stub area located at the AS tip, ABR is only one of those non-backbone area.

Commands

Note the following when configuring Stub area:

1. The backbone can not be configured as Stub area.
2. When an area is configured as Stub area, all routers in the area must be configured as Stub router. If there is a router configuration Stub, then the router and other routers in the Stub area can not become neighbors to the Stub area.
3. Stub ASBR can not exist within the region, external route can not be distributed in the region.
4. Stub area can not pass through the virtual connection established.

Here configured as Stub area Area 1, the following command:

[rtd]ospf 1
[rtd-ospf-1]area 1
[rtd-ospf-1-area-0.0.0.1]stub

[rtb]ospf 1
[rtb-ospf-1]a 1
[rtb-ospf-1-area-0.0.0.1]stub

At this point of view RTD LSA:
command display ospf lsdbto view all the router LSA

[rtd]display ospf lsdb 

	 OSPF Process 1 with Router ID 192.168.3.4
		 Link State Database 

		         Area: 0.0.0.1
 Type      LinkState ID    AdvRouter          Age  Len   Sequence   Metric
 Router    192.168.3.4     192.168.3.4        305  36    80000006       1
 Router    192.168.1.2     192.168.1.2        308  36    80000004       1
 Network   192.168.3.4     192.168.3.4        305  32    80000002       0
 Sum-Net   0.0.0.0         192.168.1.2        315  28    80000001       1
 Sum-Net   192.168.4.0     192.168.1.2        315  28    80000001       3
 Sum-Net   192.168.2.0     192.168.1.2        315  28    80000001       2
 Sum-Net   192.168.1.0     192.168.1.2        315  28    80000001       1

It found that only a class, second class, three types of LSA, there is a default three categories LSA:Sum-Net 0.0.0.0 192.168.1.2 315 28 80000001 1

View RTD route and found the default route.

<rtd>dis ip routing-table 
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Tables: Public
         Destinations : 11       Routes : 11       

Destination/Mask    Proto   Pre  Cost      Flags NextHop         Interface

        0.0.0.0/0   OSPF    10   2           D   192.168.3.2     GigabitEthernet
0/0/0 

Totally Stub Area

After you configure a Stub area, we found a router in the Stub area (Pictured: RTD) contains only a class, second class, three types of LSA. So we can understand Stub popular area, it is to cut four, five of the LSA.

But in the actual network, the network topology may be my very large, very much OSPF area, three types of LSA may be very large, which leads LSDB LSA-terminal region due to the presence of three or too large. Then we can configure Totally Stub area, reducing further three LSA entry.

Totally Stub region allows neither autonomous system external routes (four, five LSA) spread in the region, does not allow inter-area routes (three LSA) spread in the region.

Totally Stub region routers in other areas and the need for access to the external system is made three LSA ABR default route generated by the region implemented.

Stub region arranged with the difference that, in the ABR is necessary to add the no-summary.

Configuration

As Figure: On the basis of a Stub Area Area 1 disposed on the ABR will, on the RTB is added no-summaryto.

RTB configuration:

[rtb]ospf
[rtb-ospf-1]
[rtb-ospf-1]area 1
[rtb-ospf-1-area-0.0.0.1]stub no-summary 

View RTD's LSDB:

[rtd]display ospf lsdb 

	 OSPF Process 1 with Router ID 192.168.3.4
		 Link State Database 

		         Area: 0.0.0.1
 Type      LinkState ID    AdvRouter          Age  Len   Sequence   Metric
 Router    192.168.3.4     192.168.3.4         63  36    8000000B       1
 Router    192.168.1.2     192.168.1.2         68  36    80000005       1
 Network   192.168.3.4     192.168.3.4         63  32    80000002       0
 Sum-Net   0.0.0.0         192.168.1.2         74  28    80000001       1

At this point it can be found only a default LSA three categories LSA:Sum-Net 0.0.0.0 192.168.1.2 74 28 80000001 1

View the OSPF routing table:
Check the OSPF routing table commanddisplay ospf routing

[rtd]dis ospf routing 

	 OSPF Process 1 with Router ID 192.168.3.4
		  Routing Tables 

 Routing for Network 
 Destination        Cost  Type       NextHop         AdvRouter       Area
 192.168.3.0/24     1     Transit    192.168.3.4     192.168.3.4     0.0.0.1
 0.0.0.0/0          2     Inter-area 192.168.3.2     192.168.1.2     0.0.0.1

 Total Nets: 2  
 Intra Area: 1  Inter Area: 1  ASE: 0  NSSA: 0 

Can also be found, route to the outside area is a default route.

And the whole experiment configuration command

Step one: to build the topology

Build topologies, and a good distribution network segment, the proposed mark down, to avoid mistakes.

Step Two: Configure the IP address of the router

According to the allocated segments, configure all IP addresses of the router interfaces. Loopback and configure a port as an external IP address of the server address to RTF. IP can be: 192.168.6.1

For chestnut:

[RTD]
[RTD]interface GigabitEthernet 0/0/0
[RTD-GigabitEthernet0/0/0]ip address 192.168.3.4 24

Step three: OSPF area configuration and neighbors

Note: Here we divided three areas: Area 0, Area 1, Area 2. Neighbors need to be declared in different areas.

Declare neighbor command:network [相邻网段] [反子网掩码]

For chestnut:
RTA:

[RTA]ospf	
[RTA]ospf 1
[RTA-ospf-1]area 0
[RTA-ospf-1-area-0.0.0.0]network 192.168.1.0 0.0.0.255   
[RTA-ospf-1-area-0.0.0.0]network 192.168.2.0 0.0.0.255
[RTA-ospf-1-area-0.0.0.0]network 192.168.5.0 0.0.0.255

RTB:

[RTB]ospf
[RTB-ospf-1]areo 0
[RTB-ospf-1-area-0.0.0.0]network 192.168.1.0 0.0.0.255
[RTB-ospf-1-area-0.0.0.0]area 1
[RTB-ospf-1-area-0.0.0.1]network 192.168.3.0 0.0.0.255

Step Three: detecting OSPF

Once configured, the OSPF, you can continue to configure down to not worry, we can first detect what OSPF is configured correctly.

Detection command:

1. RTD can be used pingto see whether the communication RTE
2. View the routing table:display ip routing-table
3. View the OSPF routing table:display ospf routing

Step Four: introducing external routes

step 1

The exterior routing protocol is configured with RIP.

RTF：

[RTF]rip 
[RTF-rip-1]version 2    //版本2
[RTF-rip-1]network 192.168.5.0 

Step 2

important! ! !
Routing neighbors need to be declared before the introduction of the RTF will 192.168.5.0/24 network using OSPF protocol.
192.168.5.0/24 network while on the RTA declared by RIP.

RTF：

[RTF]ospf
[RTF-ospf-1]a 0
[RTF-ospf-1-area-0.0.0.0]network 192.168.5.0 0.0.0.255

RTA:

[RTA]rip 
[RTA-rip-1]v 2
[RTA-rip-1]network 192.168.5.0

Step 3

External routes. (Explained in detail to see the article: OSPF (five) OSPF external routes

RTA

[RTA]ospf
[RTA-ospf-1]import-route rip

RTF：

[RTF]rip 
[RTF-rip-1]import-route ospf 

Step Five: detecting whether or not the introduction of external routes

Detection command:

1. RTD can be used pingto see whether the RTF communication address of Loopback0
2. View the routing table:display ip routing-table
3. View the OSPF routing table:display ospf routing

Step Six: Configure Stub, Totally Stub region.

This part of the experiment above can control, will not be repeated here.