Static
Dynamic
Distance Vector
RIP
IGRP
EIGRP
MM métrica (x256)
Metrics (static values)
Bandwidth (default)
Delay (default)
Reliability
Load
Packet
Opcode
UPDATE
Propagate new information after changes
QUERY
Subtopic 1
REPLY
Response to query
HELLO
Keep-alive (5s or 60s on non-broadcast multi-access nets)
Autonomous System (AS) Number (1..65536)
Same for adjacent routers involved
Flags
Sequence
ACK
Numbers (TLV format)
Values
Hold Time
Max time to wait for HELLO (default 3x HELLO time)
K-Values (same for adjacent routers)
K1 (bandwidth)
saves mininmum bandwidth
K2
K3 (delay)
accumulation of delays
K4
K5 (reliability)
0-255
AD
EIGRP Summary Route (5)
EIGRP Internal (D) (90)
EIGRP external (DEX) (170)
Pro
Can convey internal and external information in Numbers
User Protocols Dependent Modules (PDM) for different network protocols
Complete topology overview inside AS
Cons
Requires more resources than RIP
Uses Diffusion Update Algorithm (DUAL)
Prevent routing loops
Find loop-free primary routes
Keep a list of free backup loop-routes (have different metrics thatn primary)
Concepts
Successor (S)
Lleast-cost route to the destination network
N successors means load-balancing
Feasible Distance (FD)
Lowest calculated metric to reach the destination network
Feasible Successor (FS)
Loop-free backup route
Routes for which RD_A is < FD_A
Reported Distance (RD)
Lowest calculated metric to reach the destination network
Told to a router by neighbors
Feasibility Condition (FC)
RD to a network is less that FD to a given network
Advertise Distance (AD)
Subtopic 1
Transported over Real Time Protocol (RTP)
Reliable
UPDATE
QUERY
REPLY
Unreliable
HELLO
ACK
Sent in
Unicast (bounded update)
REPLY
QUERY
Multicast (224.0.0.10)
QUERY
On cold start sends routing tables
Route summarization by default (same issue as RIP)
Use same AS number for router in same routing domain
Point auto-summarization to Null interface to avoid unecessary updates
Change interface bandwidth to a specific value
Allows manual summarization by interface
Timers can be different
If changed keep recommended ratio
Supports authentication
Process-id is the same as ASN
Link-State (LS)
Open Shortest Path First (OSPF)
Packet Header
Router ID
Area ID
Type
HELLO
Discover neighbors and build adjacencies
Usually multicast (224.0.0.5)
DATABASE DESCRIPTION (DBD)
Checks for database synchronization between router
LINK-STATE REQUEST (LSR)
Eequest specific LS records
LINK-STATE UPDATE (LSU)
Contains up to 10 LS Advertisements (LSA)
Unencrypted updates
LINK-STATE ACK (LSAck)
ACK of previous packets
Designated Router (DR)
Conveys updates to other OSPF routers
Backup DR (BDR)
Takes over DR if it fails
Hello Interval (usually 30s)
Router Dead Interval (usually 4x Hello Interval)
List of Neighbors
Authentication
Algorithm
1) LS Database
2) Apply SPF algorithm
3) SPF Tree
4) Derive "best" routing table
AD (110)
Supports authentication
Process-id is not the same as Area ID and can be different among routers in a given area
Router ID
IP address that identifies a router
Criteria to decide
1) Manually defined (# router-id)
2) Highest IP address of loopback interfaces
3) Highest IP address of active interfaces
Adjacency conditions
Same subnet masks
Routers must be in the same area (Area ID)
Must use the same authentication scheme (Authentication)
Hello and Router Dead Intervals must be equal among routers to establish adjacencies
Same Network Types
Troubleshooting
Missing or incorrect network defined
Use Loopback Address for OSPF stability because it cannot fail
Router States
1) Down
2) Init
3) 2-way
Hello to find neighbors
4) Exchange Start
How starts sending packets
5) Exchange
Exchange LSR e LSU
6) Loading
7) Full
All information is exchanged
In multi-acess networks
State = FULL, if router is DR or BDR
State = 2Way, if router is DROTHERS
No automatic summarization
Cost based on bandwidth
Based on interface bandwidth (by default 100 Mbps)
Can be modified (auto-cost reference-bandwidth)
5 network types
Point-to-Point (e.g. serial interfaces)
No DR/BDR election
Broadcast Multi-Access (BMA)
Non-Broadcast Multi-Access (NBMA)
Point-to-MultiPoint (Serial interfaces)
Virtual Links
used to transmit routing information between different areas other than 0
2 Challenges in Multi-Access Networks
Multiple Adjacencies
Excessive flooding LSA
Excessive bandwidth use + chaotic traffic
Solution
Use DR and BDR
LSA sent to 224.0.0.6 where DR/BDR are listening
DR forwards LSA to 224.0.0.5
Routers are elected to send/receive LSA
Default interface priority is 1
Election criteria precedence
1) DR (1st highest OSPF interface priority)
2) BDR (2nd highest OSPF interface priority)
3) Highest router-id
Timing of election
As soon as the 1st OSPF router enabled interface is active
DR fails
OSPF process in DR fails
Multiacess interface on DR fails
Manipulate election
1st start DR then start BDR
Sequentially change interface states
1st interface up is DR the 2nd BDR
Intermediate System-to-Intermediate System (IS-IS)
Shortest Path First (SPF) using Uses Dijkstra (based on lowest cost)
Uses LS Packet (LSP)
State of each directly connected (adjacent) link
Flood to neighbors except source of LSP
Sent
On router initial startup
After LS changes
Builds topological map
Router independently determines shortest path to all networks
Fast Convergence
Event-driven updates
Periodic HELLO to find neighbors
Cons
Higher requirements (memory, processing and bandwidth)
Link-State Routing Process
1) Router learns about its own links, its own directly connected networks
2) Each router is responsible for meeting its neighbors on directly connected networks
3) Each router builds a LSP containing the state of each directly connected link
4) Each router floods the LSP to all neighbors, who then store all LSPs received in a database
5) Each router uses the database to construct a complete map of the topology and computes the best path to each destination network
Prevents routing loops by building a complete and synchronized view of the network
Path Vector
BGP
Classification
Network classes
Classful
Classless
Update strategy
Unicast
Broadcast
Multicast
Information completeness
Partial
Full
Update targets
Bounded
Unbounded
Timing of updates
Triggered
Periodic
Use #passive-interface command to prevent sending packets out a specific interface
Table
Levels
Ultimate Route
Routes with next-hop IP address and/or exit interface
Level 1 Ultimate Route
Supernet route
Network route
Default route
Deleted when the last level 2 route is removed
Level 1 Parent route
Does not have an ultimate route
Indicates presence of level 2 routes
Created when subnets are added to the routing table
Variably subnetted
2 or more child routes with different masks belong to the same classful network
Subnetted
All child routes share the same mask
Level 2 routes (Child routes)
Subnet of a classful network address
Are Ultimate Routes
Always uses a classful scheme
Classful & Classless
Routing Protocols
how to populate routing table
Routing Behaviors
How to search routing table