Shulou(Shulou.com)06/01 Report--

08 IGRP and OSPF

8.1 introduction to EIGRP

8.1.1 characteristics of EIGRP

Cisco proprietary advanced distance vector routing protocol. Is the enhanced version of IGRP (Enhanced Interior Gateway Routing Protocol, enhanced Interior Gateway routing Protocol)

8.1.2 EIGRP table

1 neighbor table (Neighbors Table):

A list of directly connected routers that run the EIGRP routing protocol and establish an Adjacency relationship with this router. Stores the next-hop router to which the interface is connected.

2 Topology Table (Topology Table):

All route lists learned from each EIGRP neighbor. Stored FD and AD values that reach the destination network through each neighbor.

FD (Feasible Distance, feasible distance): the sum of metrics from oneself through a neighbor to the target network.

AD (Advertised Distance, advertised distance): the sum of metrics advertised by neighbors from themselves to the destination network.

3 routing table (Routing Table):

A list of the best routes obtained from the EIGRP topology table or other routing process. Stores the best route.

8.1.3 EIGRP package types

Hello package

Establish a neighbor relationship (Establish neighbor relationships)

Update package

Send routing updates (Send routing updates)

Query package

Ask your neighbor for routing information (Ask neighbors about routing information)

Reply package

Reply to routing information related to the query (Respond to query about routing information)

ACK package

Confirm a reliable packet (Acknowledge a reliable packet)

8.1.4 measures for EIGRP

1 calculation parameters of EIGRP metric: bandwidth (Bandwidth) and delay (Delay) are used by default. Reliability, load, MTU can also be used.

2 EIGRP Metric= (107 / minimum bandwidth of the link (in Kbps) + total delay of the link / 10) * 256

8.1.5 key Technologies of EIGRP

8.1.6 Discovery and recovery of neighbors

1 EIGRP Hello package:

The destination address of the Hello packet is 224.0.0.10. If the K value in the Hello packet does not match the AS number, you cannot become a neighbor. Certification must also be matched.

8.1.7 Hello timer for EIGRP

On links greater than or equal to 1.544Mbps, the default Hello Time=5s;Holdtime (hold time) = 15s.

On links less than 1.544Mbps, the default Hello Time=60s;Holdtime (hold time) = 180 s.

8.1.8 conditions for EIGRP to establish adjacency (Adjacency)

Hello packets must be transmitted through the primary address (Primary Address) of the interface

The AS number and K value in the Hello package must match to become an adjacency

The authenticated password must match

8.1.9 EIGRP reliable Transport Protocol (Reliable Transport Protocol,RTP)

1 Reliability of EIGRP

2 retransmission strategy of EIGRP (Retransmission Policy)

RTO (Retransmission Timeout, retransmission timeout) = SRTT (average round trip time) * 6terRTO5000ms, then RTO uses 5000ms.

3. Transmission mechanism of EIGRP

Window=1 of EIGRP transmission, (Stop and wait, stop mechanism)

4 reset of EIGRP neighbor

8.1.10 DUAL finite State Mechanism (Finite-State Machine,FSM)

1 DUAL terminology

DUAL: dispersion update algorithm. The routing algorithm used to calculate the best route in the EIGRP topology table.

2 the processing process of DUAL finite state mechanism

3 Successor of EIGRP

Select the path with the lowest FDvalue of all paths through the neighbor.

4 FS of EIGRP

Select the path whose AD value is less than the SUCCESSOR path FDvalue as the FS among all non-SUCCESSOR paths.

8.1.11 DUAL instance

8.1.12 Protocol dependency Module (PDM)

8.1.13 configure and check EIGRP

8.1.14 configure EIGRP

Router (config) # router eigrp [AS number (1-65535)] (make sure the AS number is the same on each router)

Router (config-router) # network [network number] [wildcard mask]

Wildcard mask (Wildcard Mask): also known as inverse mask. Use 0 to check the value of the corresponding address bit and 1 to ignore the value of the corresponding address bit.

Route (config-router) # passive-interface [Interface]

If you use this command in the RIP routing process, this interface will not send or receive RIP information; if used in the EIGRP process, this interface will not send EIGRP information, but can receive EIGRP information.

8.1.15 EIGRP check command

1 # show ip eigrp neighbors (view EIGRP's neighbor table)

2 # show ip route eigrp (D)

3 # show ip protocols

4 # show ip eigrp interface (see which interfaces on the router are running the EIGRP process)

5 # show ip eigrp topology (view the topology table of the router)

6 # show ip eigrp traffic (view the traffic of EIGRP)

7 # debup eigrp packet (current affairs view EIGRP packet delivery process)

8.1.16 8.3.3 default route for EIGRP

1 create a static default route to ISP first

2 advertise the network address connected to ISP to other routers through EIGRP

3 Router (config) # ip default-network [Network address of the main network connected to ISP]

8.1.17 8.3.4 Route Summary for EIGRP

1 automatic summary router) # auto-summary (on by default)

2 manual summary:

If) # ip summary-address eigrp [as number] [aggregated network address] [subnet mask]

8.1.18 Certification of EIGRP

Define a keychain in global mode:

RouterX (config) # key chain [chain name]

L specify a Key-id:

RouterX (config-keychain) # key [key-id]

L specify the authentication password:

RouterX (config-keychain-key) # key-string [password]

L specify the authentication method on the API:

RouterX (config-if) # ip authentication mode eigrp [autonomous-system] md5

L specify the authenticated keychain on the API:

RouterX (config-if) # ip authentication key-chain eigrp [as number] [key chain name]

8.2 introduction to OSPF

1 Link-state routing protocol: OSPF (Open Shortest Path First, Open shortest path first) protocol is an open standard link-state routing protocol that supports multi-vendor network environment.

How link-state routing protocols work:

1) each router running a link-state routing protocol learns about each of its own directly connected networks

2) each router sends Hello packets to each other to neighbors on directly connected networks

3) each router uses LSA (Link State Advertised) to establish the state of each directly connected link

4) each router floods the LSA created by itself (Flood) to all neighbors, and the neighbors store the received LSA in the link-state database (Link State DataBase,LSDB)

5) each router uses LSDB to obtain a complete topology diagram and calculate the best path to each destination network.

Link-state characteristics:

1) Link-state routing protocols can identify more network information than distance vector routing protocols.

2) Link-state routing protocols create a complete topology diagram; so routes can be accurately matched.

3) the demand for CPU and memory is high.

2 Link and link state:

Link (Link): router interface participating in the OSPF process

Link state (Link State, LS): status information of the router interface running the OSPF routing protocol, including network address, IP address, network type, link cost, neighbor information.

Link-state advertisement (Link State Advertised,LSA): sends link-state data

Link-state database (Link State DataBase,LSDB): a collection of all link-state advertisements (LSA) received; also known as a topology database

Shortest path first algorithm (Shortest Path First,SPF algorithm): an algorithm for calculating the best path in LSDB

3 link-state data structure

1) neighbor table: also known as adjacency database (Adjacency Database)

2) Topology table: also known as topology database; also known as link-state database (Link-state Database,LSDB)

3) routing table: also known as forwarding database (Forward Database).

4 network layering of link-state routing protocols

1) the level of the area:

Backbone area (Backbone Area), also known as transmission area (Transit Area)

Standard area: also known as non-backbone area.

Routers in the area exchange LSA with the router, forming the same LSDB; to exchange routing information between areas, so all other non-backbone areas must be connected to the backbone area through physical or logical links (Virtual Link, virtual links).

2) Design principles of OSPF area:

A. All non-backbone areas must be directly connected to the backbone area (Area 0)

The demarcation of B and OSPF areas is on the router, that is, the same physical link must belong to the same area.

3) the advantages of OSPF regional design:

A. minimize routing entries. Because routing information is exchanged between areas, non-backbone areas can create default routes to backbone areas to minimize routing entries; default routes to backbone areas can be achieved by configuring non-backbone areas as stub areas (Stub Area).

B, the change of link state in the area only affects the router in the local area. The link state change in the area is to affect the router in the local area by flooding (Flood) LSA. The LSA with link state change in the area will not be flooded to other areas and will not affect the routers in other areas.

4) terminology of the region

Backbone router: router in area 0

Internal routers: routers in standard area

Area Border Router (Area Border Router,ABR): the router responsible for connecting the standard area to the backbone area.

Autonomous system Border Router (Autonomous System Border Router,ASBR): a router that connects OSPF management domains to other autonomous systems.

Adjacency of 5 OSPF

(1) on point-to-point WAN links: two neighbors are completely adjacent (Full Adjacency)

(2) multiple access (Multiaccess) network: neighbors only establish complete adjacencies with DR and BDR.

DR (Designated Router, designated router): a router responsible for establishing adjacencies with other routers in a multiaccess network

BDR (Backup designated Router, backup designated router): backup of DR.

DRother (other routers): for routers other than DR and BDR, DRother and DRother cannot form an adjacency and form a yes neighbor relationship.

6 OSPF calculation

SPF algorithm:

7 the operation of LSA

LSA (Link-state Advertise, link-state advertisement)

8 package type of OSPF

Type 1:Hello package

Type 2:DBD/DDP package (Database Description database description package): LSDB summary information.

Type 3:LSR packet (Link-state Request, link-state request packet):

Type 4:LSU packet (Link-state Update, link-state update package):

Type 5:LSAck: link-state acknowledgement packet.

9 the header format of the OSPF packet:

Hello package header format:

1) version: OSPFv2

2) package type: Type 1

3) Total packet length:

4) Router ID (RID): indicates the router that sent the packet, consisting of the highest IP address of all logical interfaces, or the highest IP address of the physical interface if there is no logical interface

5) Area ID: area ID, indicating the area where the interface that sent the packet is located

6) Checksum: verification

7) Authentication Type: authentication type, using 0x0000 to indicate that authentication is not used, 0x0001 for authentication using plaintext, and 0x0002 for authentication using MD5

8) Authentication: password for authentication

2 neighbor relationship-Hello package

The destination address of the Hello packet is 224.0.0.5

The size of the Hello package is 50byte.

The default is: Hello Time=10s Dead Interval Time (interval between death) = 40s.

Conditions for OSPF to establish a neighbor relationship:

1) Area ID must be consistent; 2) Hello Time and Dead Interval Time must be consistent; 3) the authentication method and password must be the same; 4) Stub Flag (stub area flag must be consistent); 5) the OSPF network type of the interface connecting the two routers must be the same. (Ethernet interface default OSPF network type is Broadcast; serial interface and default encapsulated OSPF network type is Point to Point)

3 establish two-way communication (one phase)

After three states:

1) Down state (failure status)

2) Init State (initial state)

3) 2-way state (bidirectional status)

4 Discovery of network routes (phase 2)

4) Exstart state (pre-startup status): select the status of the master (Master) / slave (Slave) router. The larger interface RID sends the DBD packet first as the Master router, and the smaller interface RID sends the DBD packet as the Slave router.

5) Exchange state (exchange status): the process of sending DBD packets to each other.

5 entries for increasing link state (three phases)

6) Loading state (loading status):

7) Full state (full adjacency status): the status of LSDB full synchronization.

6 maintain routing information

1) when the network changes, the router that changes sends DR and BDR;DR with address 224.0.0.6 through LSU, and then sends the LSU with 224.0.0.5 to all routers that have established adjacencies with them.

2) when there is no change in the network, the source router that generated the LSA will Flood every 30 minutes to all routers that have established adjacencies with themselves.

8.6 configure OSPF routing protocol

8.6.1 basic configuration of OSPF

Router (config) # router ospf [process ID, process number, 1-65535]

Process Identifier (process ID): it is locally meaningful and can be inconsistent with the process ID of other routers; used to identify a unique OSPF database.

Router (config-router) # network [network number / address] [wildcard mask] area [0232]

Use of wildcard masks:

Use 0 to check the value of the address bit that matches; use 1 to indicate the value of ignoring the address that matches.

10 check the configuration of OSPF

1 # show ip protocols

2 # show ip route ospf (O)

OSPF does not support automatic summarization, only manual summarization.

The measure of OSPF is expressed in terms of COST. COST=108/ bandwidth (in bps) under Cisco IOS

3 # show ip ospf interface [API] (check whether the API is running OSPF)

4 # show ip ospf (check the operation of OSPF on the router)

5 # show ip ospf neighbors (view neighbor information of OSPF)

6 # show ip ospf database (check the LSDB of OSPF)

11 types of LSA: 11 in total

1), Type 1 LSA: router LSA (Router LSA), issued by all routers in the area

2), Type 2 LSA: network LSA (Network LSA), issued by the DR router

3), Type 3 LSA: summary Network LSA (Summary Network LSA): issued by ABR (area Border Router)

7 # debug ip ospf packets (check the operation of the OSPF package on current affairs)

8 # debug ip ospf events (check the event information of OSPF for current affairs)

8.7 Network types of OSPF

8.7.1 Point-to-Point Network (Point to point)

DR and BDR are not elected.

8.7.2 broadcast multiple access Network (Broadcast Multiaccess)

You need to select DR and BDR.

Use the router with the highest priority of the interface as the DR for this segment, and the interface priority running the OSPF process defaults to 1. You can manually adjust the priority of the interface:

-if) # ip ospf priority [0,255]

The router with the highest priority is DR, the second highest router is BDR, and the other router is DRother. A priority of 0 can never be elected as DR or BDR.

Restart the routing process of OSPF: # clear ip ospf process

If the priority is exactly the same, choose the router with the largest RID as the DR, the second largest router as the BDR, and the other routers as the DRother.

RID (Router ID): consists of the highest IP address of the router's logical interface, or the highest IP address of the physical interface if there is no logical interface.

8.7.3 NBMA (Non-Broadcast Multiacess, non-broadcast multiaccess)

Manually specify neighbors, manually specify DR and BDR

Five modes in NBMA Network

Configuration options for 8.8 OSPF

8.8.1 specify the RID of the OSPF

Router (config-rouer) # router-id [RID address]

8.8.2 configure a default route for OSPF

Router (config-router) # default-information originate [always] [Metricvalue]

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