<span dir="rtl">OSPF و EIGRP در رد - oshaghi.net</span>

cloutedcoughNetworking and Communications

Oct 28, 2013 (3 years and 9 months ago)

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OSPF
و
EIGRP
در(../

رد

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Shafagh Zandi
http://www.shafagh.com
http://blog.shafagh.com/persian
Sunday, September 18, 2011
ROUTING PROTOCOLS

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Routers language to share information about the reachability and status of
networks.
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Sunday, September 18, 2011
ROUTING PROTOCOLS
IP
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1. IP Routing is Destination Based.
2. Routing occurs per hop.
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Sunday, September 18, 2011
ROUTING PROTOCOLS
Static Routing
Dynamic Routing
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Sunday, September 18, 2011
DYNAMIC ROUTING
All dynamic routing protocols are built around an algorithm
to provide:
1. Path Determination
2. Metrics
3. Convergence
4. Load Balancing
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Sunday, September 18, 2011
DYNAMIC ROUTING PROTOCOLS
IGP - Interior Gateway Protocol
EGP - Exterior Gateway Protocol
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Sunday, September 18, 2011
DYNAMIC ROUTING PROTOCOLS
Distance Vector Protocols
Link State Protocols
Path Vector Protocols
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Sunday, September 18, 2011
DYNAMIC ROUTING PROTOCOLS
Distance Vector Protocols
RIP, IGRP
Link State Protocols
OSPF, IS-IS
Path Vector Protocols
BGP
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Sunday, September 18, 2011
EIGRP
Minimal use of network resources
Restricted use of network when there’s a change (Paces)
Rapid Convergence
Scalability - No periodic updates
EIGRP
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Sunday, September 18, 2011
EIGRP
Neighbor Relationship
Loop-free Path Calculation
Querying neighbors to find unknown paths
EIGRP
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یاBCا
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Sunday, September 18, 2011
EIGRP NEIGHBOR RELATIONSHIP

EIGRP conserves network bandwidth by non-periodic, incremental updates.

Topology changes are transmitted when needed.

If a neighbor is reachable, the path is assumed to be valid.

EIGRP relies on Neighbor relationships!
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Sunday, September 18, 2011
EIGRP NEIGHBOR RELATIONSHIP

5-second hellos for Ethernet (Broadcast Media) and Point-to-Point links

60-second hellos for slow multipoint links ( T1 )

Hold time  3x Hello (by default)  15 second for Broadcast/P2P links.

ip eigrp hello-interval

ip eigrp hold-time
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Sunday, September 18, 2011
EIGRP NEIGHBOR RELATIONSHIP

Neighbors can have different timers set, because the hold timer is included in hello
packets.
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Sunday, September 18, 2011
EIGRP METRIC

EIGRP uses the minimum bandwidth and the total delay to compute metric.

EIGRP uses bandwidth and delay (by default) to compute composite metric.
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Sunday, September 18, 2011
EIGRP LOOP-FREE ROUTES

Distance to destination advertised by the neighbor 
reported distance

The best metric available to the network 
feasible distance

The neighbor with the best metric to a destination 
successor

Any neighbors whose reported distances are less than the FD 
feasible successor
A
B
C
D
E
1
1
1
1
1
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Sunday, September 18, 2011
CLEARING TOPOLOGY TABLE

EIGRP uses non-periodic updates, it does not time routers out of its table

The route must be removed by new information from a neighbor or through tearing
down a neighbor relationship.
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Sunday, September 18, 2011
EIGRP QUERY

If a router loses a route to a destination (and it has no FS) it goes active.

EIGRP queries each of its neighbors to see if any of them has another path.

to learn filtered routes (DUAL, Split Horizon, etc)

to inform neighbors that has no longer a path to this network.
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Sunday, September 18, 2011
EIGRP QUERY

If a route remained active for three minutes, it is considered SIA (STUCK IN ACTIVE)

When a route is SIA, the neighbor that has not answered is reinitialized

clearing SIA route

clearing all other routes through that neighbor
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Sunday, September 18, 2011
BOUNDING QUERIES

Summarization

EIGRP Stub Routers

Distribution Lists
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Sunday, September 18, 2011
EIGRP SUMMARIZATION

Auto-summary (Internal routes)

Manual-summarization (Internal and External routes)

Route is created to interface null0

Advertise the summary out of the interface

Advertise the components of this summary as unreachable
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Sunday, September 18, 2011
EIGRP LOAD BALANCING

Equal-cost paths

Unequal-cost paths

uses Variance

Path metrics: 100,200,300,400

Variance  3
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Sunday, September 18, 2011
EIGRP SUMMARY
Uses IP Protocol 88 and RTP (Reliable Transport Protocol)
Diffusing Update Algorithm (DUAL)
Full updates first - Partial updates after route change.
EIGRP supports MD5 Authentication only.
Auto summary is enabled by default.
Split horizon is enabled by default.
VLSM support and route summarization.
Route tags for redistribution
Supports advertisement of Next-hop router.
Multi-protocol support: advertises IPX and AppleTalk routes.
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Sunday, September 18, 2011
OSPF

RFC 2328

OSPF advertises the state of its directly connected links to all routers (Flooding)

OSPF uses long periodic updates

Routers perform SPF - Shortest Path First to find a loop-free path to each destination.
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Sunday, September 18, 2011
OSPF ROUTER ID

Each OSPF router must have a unique identifier  Router ID

Router ID and LSA Sequence number are used to detect duplicate LSAs.

Router ID is highest IP address from any operational interface (up/up)
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Sunday, September 18, 2011
OSPF PACKET TYPES

     Hello - Neighbor Discovery/Maintenance

     DBD - Database Description

     LSR - Database Download Request

     LSU - Database Update

     LSAck - Flooding Acknowledgement
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Sunday, September 18, 2011
OSPF NEIGHBOR TIMERS

     Fast Timer: Hello 10, Dead 40

     Slow Timer: Hello 30, Dead 120
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Sunday, September 18, 2011
OSPF NEIGHBORS

     Area ID and Area Type

     Authentication

     Network Mask (ignores subnet mask on P2P)

     Hello Interval

     Router Dead Interval

     Options

     MTU (not part of Hello) MTU is part of DD packets.
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Sunday, September 18, 2011
OSPF DESIGNATED ROUTER

     
Goal
: Optimizing LSA flooding process on multi-access links with use of pseudo-node

     DR represent the multi-access network (by LSA2) and forms adjacency with others.

     Selection of DR is not per router basis, but per interface.

     DR election: Higher priority (1-255)  higher RID

          DR is elected based on Router Priority, which is an 8-bit value. (0 to 255) Default1

          Equal the priorities then the neighbor with the highest Router ID will be chosen.

     Priority of 0 means no intention to become the DR or BDR.

     DRothers send update packets to the AllDRouters (224.0.0.6)

     All routers continue to multicast Hellos to the AllSPFRouters (224.0.0.5)

     DR floods the updates to AllSPFRouters (224.0.0.5)
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Sunday, September 18, 2011
OSPF LSA TYPES

Router Link State - Type 1

Network Link State - Type 2

Summary Link State - Type 3

Summary ASBR Link State - Type 4

External Network Link State - Type 5

External Network Link State - Type 7
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Sunday, September 18, 2011
OSPF AREAS

Area 0  Backbone Area

Area x  non-transit flooding domain

Stubby Area  External routers are not flooded but internal summaries are.

Totally Stubby Area  All routers receive a default route only from ABR.

Not-So-Stubby Area (NSSA)  External connection to another AS is permitted.
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Sunday, September 18, 2011
OSPF FINITE STATE MACHINE

    
Down

    
Attempt
(only on NBMA)

    
Init
- Hello is seen

    
2-Way
- own RID is seen in Hello from neighbor

    
ExStart
- Master/Slave relation (highest RID) Slave sets MS-bit  0

    
Exchange
- Database Description and LSRs

    
Loading
- Transfer LSAs (LSR,LSU, LSAck)

    
Full
- Adjacent
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Sunday, September 18, 2011
OSPF VIRTUAL LINK

Allowing traffic to traverse to and from the backbone area to pass through another
area.

Must be configured between two ABRs.

Transit area must have full routing table and cannot be a stub area.
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Sunday, September 18, 2011
OSPF SUMMARY
Developed by OSPF working group at IETF
Classified as an IGP
Uses IP Protocol 89
Dijkstra Algorithm to calculate SPF
Metric: Cost (per interface)
ALLSPFRouters: 224.0.0.5
ALLDRouters: 224.0.0.6
Default OSPF DR Priority: 1
Full LSDB topology sync first, then partial LSA flooding.
VLSM and Route tags are supported.
Summarization at Area boundary.
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Sunday, September 18, 2011
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Router A
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192.168.2.0/24
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Sunday, September 18, 2011
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Sunday, September 18, 2011
۳

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Router-4
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ب$M:1ا
A. Change the bandwidth on the link between Router2 and Router5 to 70
B. Change the bandwidth on the link between Router1 and Router3 to 80
C. Change the bandwidth on the link between Router3 and Router5 to 70
D. Change the bandwidth on the link between Router4 and Router5 to 110
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Sunday, September 18, 2011
۴

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OSPF
رد
NET-B
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NET-A
زا

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ب$M:1ا
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Sunday, September 18, 2011
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Sunday, September 18, 2011