OSPF multi-region Data Stream Analysis (2)

 

RT2 receives the route, saves it to LSDB, calculates the route, and installs the optimal route to the global route table:

O * IA 0.0.0.0/0 [110/65] via 10.2.26.2, 00:07:10, Serial0/2

O * IA indicates the three default routes delivered

Measurement Value: S0/2 + LSA overhead = 64 + 1 = 65

In RT2, a single-point bidirectional redistribution is performed to re-distribute OSPF routes to RIP. RT4 runs the RIP Protocol and learns the route information:

The routing information in the RIP database is:

0.0.0.0/0

[5] via 172.16.24.1, 00:00:00, Serial0/0

Global Path table of RT4:

R * 0.0.0.0/0 [120/5] via 172.16.24.1, 00:00:20, Serial0/0

R indicates the RIP Protocol * indicates the default route

The management distance is 120, and the measurement value is 5 (5 for redistribution, the default value is 15)

Now you can go to RT3 on RT4!

Route Propagation Analysis on RT4:

Direct Connection routing on RT4:

C 172.16.4.0/24 is directly connected, Ethernet3/0

The Routes learned to RT4 through RIP on RT2:

R 172.16.4.0/24 [120/1] via 172.16.24.2, 00:00:01, Serial0/0

Redistributes RIP routes to OSPF on RT2 and summarizes external routes at the same time:

LS age: 271

Options: (No TOS-capability, Type 7/5 translation, DC)

LS Type: AS External Link // AS External route

Link State ID: 172.16.0.0 (External Network Number) // LSID172.16.0.0

Advertising Router: 2.2.2.2 // advertise vroid ID 2.2.2.2

LS Seq Number: 80000001

Checksum: 0xEC21

Length: 36

Network Mask:/16 // 16-bit Network Mask

Metric Type: 1 (Comparable directly to link state metric) // re-release Type 1

TOS: 0

Metric: 1000 // The overhead is 1000, Which is manually specified

Forward Address: 2.2.2.2 // the forwarding Address is 2.2.2.2 (Class 7 is generally ROUTER-ID)

External Route Tag: 0

After receiving the LSA of the 7 types of summary routes, RT6 saves them to LSDB, calculates the routes, selects the optimal routes, installs them in the global routing table, and converts the 7 types of LSA into 5 types of LSA:

O N1 172.16.0.0/16 [110/1065] via 10.2.26.1, 00:05:03, Serial0/0

N1: The NSSA region is type 1.

Metric value = overhead reaching the forwarding address + LSA overhead = 65 + 1000 = 1065

LS age: 27

Options: (No TOS-capability, DC)

LS Type: AS External Link

Link State ID: 172.16.0.0 (External Network Number)

Advertising Router: 6.6.6.6 // notice the vroabr ID, 7 to 5 by the ABR notice, when there are multiple nssa abr, The ROUTER-ID large to do 7 to 5, after expiration, the other one performs 7 to 5.

LS Seq Number: 80000004

Checksum: 0x302

Length: 36

Network Mask:/16 // 16-bit Network Mask

Metric Type: 1 (Comparable directly to link state metric)

TOS: 0

Metric: 1000 // The overhead is 1000, Which is manually specified

Forward Address: 2.2.2.2 // the forwarding Address 2.2.2.2, used to identify the next hop route to the external route

External Route Tag: 0

When RT5 receives 5 types of LSA, it saves it to LSDB, calculates the route, selects the optimal route, installs it in the global route table, and floods the LSA outward:

O E1 172.16.0.0/16 [110/1129] via 10.0.56.2, 00:04:32, Serial0/1

E1: five types of LSA external routes with the overhead type of 1

Metric value = overhead reaching the forwarding address + LSA overhead = S0/1 + S0/0 + LOOP0 + 1000 = 64 + 64 + 1 + 1000 = 1129

RT5 is an outbound LSA without changing any content:

Routing Bit Set on this LSA

LS age: 192

Options: (No TOS-capability, DC)

LS Type: AS External Link

Link State ID: 172.16.0.0 (External Network Number)

Advertising Router: 6.6.6.6

LS Seq Number: 80000004

Checksum: 0x302

Length: 36

Network Mask:/16

Metric Type: 1 (Comparable directly to link state metric)

TOS: 0

Metric: 1000

Forward Address: 2.2.2.2

External Route Tag: 0

The overhead for reaching the forwarding address is advertised by R6. When calculating the external overhead, the overhead for arriving at RT6 is added:

Routing Bit Set on this LSA

LS age: 674

Options: (No TOS-capability, DC, Upward)

LS Type: Summary Links (Network)

Link State ID: 2.2.2.2 (summary Network Number)

Advertising Router: 6.6.6.6

LS Seq Number: 80000001

Checksum: 0x5D6

Length: 28

Network Mask:/32

TOS: 0 Metric: 65

After receiving the extensive LSA of RT5, RT1 saves it to LSDB, calculates the route, and selects the optimal route to install it in the global route table. Because RT5 implements the complete peripheral area and filters out three types of LSA, therefore, a default LSA is issued to Region 1 to enable the router of Region 1 to go to RT4:

O E1 172.16.0.0/16 [110/1193] via 10.0.15.2, 00:06:21, Serial0/2

Five types of LSA received by RT1, which are not changed when RT6 is sent:

Routing Bit Set on this LSA

LS age: 440

Options: (No TOS-capability, DC)

LS Type: AS External Link

Link State ID: 172.16.0.0 (External Network Number)

Advertising Router: 6.6.6.6

LS Seq Number: 80000004

Checksum: 0x302

Length: 36

Network Mask:/16

Metric Type: 1 (Comparable directly to link state metric)

TOS: 0

Metric: 1000

Forward Address: 2.2.2.2

External Route Tag: 0

Three default LSA types issued by RT1 to Region 1:

LS age: 958

Options: (No TOS-capability, DC, Upward)

LS Type: Summary Links (Network) // Network Summary LSA Class 3 LSA

Link State ID: 0.0.0.0 (summary Network Number) // LSID 0.0.0.0

Advertising Router: 1.1.1.1 // advertise the vroabr as ABR

LS Seq Number: 80000001

Checksum: 0x93A6

Length: 28

Network Mask:/0 // Mask is 0, default route

TOS: 0 Metric: 1 // The default overhead is 1, and the default-metric Metric value can be used to modify the overhead of the default route.

RT3 receives three default LSAs, saves them to LSDB, calculates the route, and selects the optimal route to install it in the global route table:

O * IA 0.0.0.0/0 [110/65] via 10.1.13.1, 00:16:08, Serial0/0

Metric value = S0/0 + LSA overhead = 64 + 1 = 65

LSA stored in RT3 LSDB

LS age: 958

Options: (No TOS-capability, DC, Upward)

LS Type: Summary Links (Network)

Link State ID: 0.0.0.0 (summary Network Number)

Advertising Router: 1.1.1.1

LS Seq Number: 80000001

Checksum: 0x93A6

Length: 28

Network Mask:/0

TOS: 0 Metric: 1

The routers in some regions 1 can go to RT4, and there will also be back routes! Analysis ends now! Follow the experiment analysis in the next section! The blog is constantly updated!

This article is from the "Mortal World" blog