ccna2 m7 distance vector routing protocol
TRANSCRIPT
-
8/14/2019 CCNA2 M7 Distance Vector Routing Protocol
1/22
CCNA Semester2
Module 7Routing and Routing Protocols
Objectives
Distance vector routing
RIP IGRP
-
8/14/2019 CCNA2 M7 Distance Vector Routing Protocol
2/22
-
8/14/2019 CCNA2 M7 Distance Vector Routing Protocol
3/22
Distance vector routing loop issues
Routing decisions based on incorrect information results in packets takingpaths that return them to already visited routers
Before network 1 goes down B & D goes via A to this network, C may go via Bto this network
When net 1 is down, A informs B & D about it, C does not yet know
C sends update to D informing that it canget to net 1 via B
D updates this incorrect route overwritingthe previously correct update from A
D sends update to A followed by A sendsupdate to B causing both A & B to alsoupdate the incorrect route
Consequence: Packet originating from Cdestined to net 1 will loop:
C B A D C
Problem: Count to infinity Large number of routing loops results in forever-increasing value of routing
metric, e.g. hop count, or count to infinity
-
8/14/2019 CCNA2 M7 Distance Vector Routing Protocol
4/22
-
8/14/2019 CCNA2 M7 Distance Vector Routing Protocol
5/22
Route poisoning
To overcome large routing loops Set the hop count to one more than the maximum.
Avoiding routing loops with triggered updates
Triggered update is sent immediately in response tosome change in the routing table.
Triggered updates, used in conjunction with routepoisoning, ensure that all routers know of failed routesbefore any holddown timers can expire.
-
8/14/2019 CCNA2 M7 Distance Vector Routing Protocol
6/22
Loop prevention: Hold-down timer
If at any time during hold-down timer an update is received from The same neighbor indicating that the network isagain accessible, the router marks
the network as accessible and removes the hold-down timer. A different neighboring router with abetter metricthan originally recorded for the
network, the router marks the network as accessible and removes the hold-downtimer.
A different neighboring router with apoorer metric, the update is ignored.
Routing Information Protocol- RIP -
-
8/14/2019 CCNA2 M7 Distance Vector Routing Protocol
7/22
Classful Routing vs. Classless Routing
Classful routing must be used with classfulnetwork or subnets with the same subnetmask.
It does not include subnetmask in its routingtable (FLSM) Classless routing allows updating routes with
different subnetmasks therefore it includesubnetmask in routing update (VLSM)
RIP
Distance vector protocol Hop count is used as the metric for path
selection Maximum hop count is 15 Routing update interval is 30s
-
8/14/2019 CCNA2 M7 Distance Vector Routing Protocol
8/22
RIPv1 and RIPv2
RIP Version 1 is a Classful Routing Protocol, RIP Version 2is a Classless Routing Protocol. RIP v2 enhancementsinclude: Ability to carry additional packet routing information. Authentication mechanism to secure table updates.
Supports variable length subnet masking (VLSM).
Configuring RIP
-
8/14/2019 CCNA2 M7 Distance Vector Routing Protocol
9/22
-
8/14/2019 CCNA2 M7 Distance Vector Routing Protocol
10/22
Configure RIPv1 and RIPv2
Show ip protocols
-
8/14/2019 CCNA2 M7 Distance Vector Routing Protocol
11/22
SHOW IP ROUTE command
Show ip route
R 183.8.0.128 [120/1] via 183.8.128.130 , 00:00:17 , Serial0
via 183.8.64.130 , 00:00:17 , Serial1
183.8.0.128 : destination network number
[120/1] : [administrative distance/hop count]
183.8.128.130 : next hop IP address
00:00:17 : latest update was 17 seconds ago
Serial0 : outgoing interface is Serial0
Second line : load sharing
-
8/14/2019 CCNA2 M7 Distance Vector Routing Protocol
12/22
Troubleshooting RIP update issues
Other commands to troubleshoot RIP: show ip rip database
show ip protocols show ip route debug ip rip {events} show ip interface brief
Load Balancing with RIP
-
8/14/2019 CCNA2 M7 Distance Vector Routing Protocol
13/22
-
8/14/2019 CCNA2 M7 Distance Vector Routing Protocol
14/22
Interior Gateway Routing Protocol- IGRP -
IGRP
IGRP is a distance vector routing protocoldeveloped by Cisco .
IGRP sends routing updates at 90 secondintervals, advertising networks for a particular autonomous system .
-
8/14/2019 CCNA2 M7 Distance Vector Routing Protocol
15/22
IGRP features
Key design characteristics of IGRP are a follows: The versatility to automatically handle indefinite, complex topologies The flexibility needed to segment with different bandwidth and delay
characteristics Scalability for functioning in very large networks
IGRP Metrics
The metrics that IGRP uses are: Bandwidth The lowest bandwidth value in the path Delay The cumulative interface delay along the path Reliability The reliability on the link towards the destination as determined
by the exchange of keepalives Load The load on a link towards the destination based on bits per second MTU The Maximum Transmission Unit value of the path.
Default metric use only bandwidth and delay Hop-count is used as a secondary metric to prevent loop
-
8/14/2019 CCNA2 M7 Distance Vector Routing Protocol
16/22
SHOW IP PROTOCOLS command
IGRP routes
IGRP advertises three types of routes: Interior System Exterior
-
8/14/2019 CCNA2 M7 Distance Vector Routing Protocol
17/22
IGRP Routes
AS = 100 AS = 200
Configuring IGRP
-
8/14/2019 CCNA2 M7 Distance Vector Routing Protocol
18/22
Verifying IGRP configuration
Additional commands for checking IGRPconfiguration are as follows:
show interface interface [brief] show running-config show ip protocols
Troubleshooting IGRP
The following commands are useful whentroubleshooting IGRP: show ip protocols show ip route debug ip igrp events
debug ip igrp transactions ping traceroute
-
8/14/2019 CCNA2 M7 Distance Vector Routing Protocol
19/22
Default static ip route
Create a default route on the router which isbeing configured:
ip route 0.0.0.0 0.0.0.0 { ip_next_hop | interface } Static routes can be advertised to other router
via dynamic routing update using:redistribute static
IGRP has no concept of route 0.0.0.0/0
Default Network
Tell other router to choose the network as thedefault route:
ip default-network { network_number }
Network_number must be a known classfullnetwork (taken from routing table)
IGRP may use this with default static ip route For a network, default route configuration is
only configured on gateway router
-
8/14/2019 CCNA2 M7 Distance Vector Routing Protocol
20/22
Default Route
Summary
How routing loops occur in distance vector Preventing routing loop solution Configuring RIP IGRP features
IGRP metrics IGRP routes Configuring IGRP
-
8/14/2019 CCNA2 M7 Distance Vector Routing Protocol
21/22
Lab Topology 1 - RIP
Lab_A
Lab_B
Lab_C
S0/0
S0/1
S0/0
F0/0
S0/1
F0/0
Lab_D
Lab_E
Lab_F
S0/0
S0/1
S0/0
F0/0
S0/1
F0/0
F0/0 F0/0
S0/1S0/0
Site1 Site2
Port Lab_A Lab_B Lab_C Lab_D Lab_E Lab_F
S0/0 201.10.11.1/24 199.6.13.1/24 204.204.7.1/24 192.168.3.1/24
204.204.7.2/24
172.18.11.1/16
34.10.120.1/16 N/A
S0/1 N/A 201.10.11.2/24 199.6.13.2/24 192.168.3.2/24 34.10.210.5/16
F0/0 172.17.11.1/16 172.16.11.1/16 172.17.11.2/16 172.16.11.2/16 172.18.11.2/16
Lab Topology 2 2 IGRP AS with default routes
Internet
Lab_A
Lab_B
Lab_C Lab_D
Lab_E
Lab_F
IGRP 100172.20.0.0/16
IGRP 200192.168.1.0/24
172.16.2.1/16 172.16.2.2/16
-
8/14/2019 CCNA2 M7 Distance Vector Routing Protocol
22/22
CCNA2 Module7