Rahul Khadse
This type of routing is based on link state. Its working is
explain as under
(1) Each router will send Hello packets to all neighbors
using all interfaces.
(2) The router from which Hello reply receive are
stored in the neighborship table. Hello packets are send periodically to maintain the
neighbor table.
(3) The router will send link state information
to the all neighbors. Link state information from one neighbor is also forwarded to other
neighbor.
(4) Each router will maintain its link state
database created from link state advertisement received from different router.
(5) The router will use best path algorithm to
store the path in routing table.
Neighbor Topology
Routing
11.0.0.1 R1
11.0.0.0 dc
13.0.0.2 12.0.0.0 dc
13.0.0.0 dc
R2 11.0.0.0
10.0.0.0
R3 13.0.0.0
14.0.0.0
15.0.0.0
16.0.0.0
R4 16.0.0.0
17.0.0.0
R5 18.0.0.0
19.0.0.0
20.0.0.0
14.0.0.0
R6 20.0.0.0
21.0.0.0
Problems of Link
State
The main problems of link state routing are: -
(1) High bandwidth consumption.
(2) More hardware resources required that is processor and
memory (RAM)
The routing protocols, which use link state routing are: -
(1) OSPF
(2) EIGRP
Enhanced Interior Gateway Routing Protocol
Features: -
* Cisco proprietary
* Hybrid protocol
Distance
Vector
* Multicast Updates using
Address
224.0.0.10
* Support AS
* Support VLSM
* Automatic Route Summarization
* Unequal path cost load balancing
* Metric (32 bit composite)
Bandwidth
Delay
Load
Reliability
MTU
* Neighbor Recovery
* Partial updates
* Triggered updates
* Backup Route
* Multi Protocol Routing
EIGRP Protocols & Modules
(1) Protocol depended module
Reliable Transport Protocol (Quiet Protocol)
RTP is used to exchange routing updates with neighbor
routers. It will also maintain neighbor relationship with the help of Hello packet. RTP has
following features: -
(1) Multicast updates (224.0.0.10)
(2) Neighbor recovery
If neighbor
stops responding to the Hello packets then RTP will send unicast Hello packet for that neighbor.
(3) Partial updates
(4) No updates are send if there is no topology change.
Diffusing Update Algorithm (DUAL)
DUAL is responsible for calculating best path from the
topology table. Dual has following features: -
* Backup Path
* VLSM
* Route queries to neighbor for unknown n/w
Configuring EIGRP
Router(config)#router eigrp <as no>
Router(config-router)#network <net addr.>
Router(config-router)#network <net addr.>
Router(config-router)#exit
Advanced Configuration EIGRP
Configuring following options are same as configuring IGRP
(1) Bandwidth on Interfaces
(2) Neighbor
(3) Load balancing
Max path
Variance
Configuring EIGRP Metric
If we want our router to use additional metric then we can
use following command: -
Router(config)#Router eigrp <as no>
Router(config-router)#metric weights 0
<k1> <k2> <k3> <k4> <k5>
Type
of service (default) 1
0 1 0
0
Router(config-router)#exit
Metric K Default value
Bandwidth K1 1
Load K2 0
Delay K3 1
Reliability K4 0
MTU K5 0
All routers exchanging update with each other must have same
AS no. and same K value.
To up the Ethernet without connect wireRouter(config)#int eth0
Router(config-if)#no keepalive
Router#clear ip route *
Hush routing table and again make it.
Router#sh ip eigrp topology
It shows topology database.
P-> passive->stable
A->active->under updation
Router#sh ip eigrp neighbor
It shows neighbor table
Router#redistribute <protocol> ?
Metric also need to be modified
Debug IGRP
Router#debug ip igrp events
Router#debug ip igrp transactions
It shows every update
Debug EIGRP
Router#debug ip eigrp
Router#debug ip eigrp summary
For few debug
Open Shortest Path First
Features: -
* Link
State
* Open standard
* Multicast updates
224.0.0.5
224.0.0.6
* Support VLSM
* Support Area similar to AS
* Manual Route Summarization
* Hierarchical model
* Metric
Bandwidth
* Equal path cost load balancing
* Support authentication
* Unlimited hop count
OSPF Terminology
Already known topics in this: -
(1) Hello packets
(2) LSA (Link
State
(3) Neighbor
(4) Neighbor table
(5) Topology table (LSA database)
Router ID
Router ID is the highest IP address of router
interfaces. This id is used as the identity of the router. It maintaining link state databases.
The first preference for selecting router ID is given to the Logical interfaces. If logical
interface is not present then highest IP of physical interface is selected as router id.
Adjacency
A router is called adjacency when neighbor relationship is established. We can also say adjacency relationship is formed between the routers.
Area Router (Autonomous System Border Router – ASBR)
A router, which has all interfaces member of single area, is called area router.
Backbone Area
Area 0 is called backbone area. All other areas must connect to the backbone area for communication.
Backbone Router
A router, which has all interfaces members of area 0, is called backbone router.
..
Area Border Router
A router, which connects an area with area 0, is
called area border router.
LSA Flooding in OSPF
If there are multiple OSPF routers on multi access n/w
then there will be excessive no. of LSA generated by the router and they can choke
bandwidth of the network.
This problem is solved with the help of electing a router as designated router and backup designated router.
Designated Router :-->> A router with highest RID (router id) will be designated router for a particular interface. This router is responsible for receiving LSA from non-DR router and forward LSA to the all DR router.
Backup Designated Router :-- This router will work as backup for the designated router. In BDR mode, it will receive all information but do not forward this information to other non-DR router.
Commands to configure OSPF
Router#conf ter
255.255.255.255
Router(config)#router ospf <process no>
Router(config-router)#network <net address> <wild
mask> area <area id>
Router(config-router)#network <net address> <wild
mask> area <area id>
Router(config-router)#exit
Wild Mask – Complement of subnet mask
Example 255.255.0.0
0.0.255.255
255.255.255.255
- Subnet mask
------------------------
Wild mask
-
255.255.192.0 subnet mask
--------------------------------------
0.0.63.255 wild mask
Router(config)#router ospf 32
Router(config-router)#network 200.100.100.0 0.0.0.255 area
20
Router(config-router)#network 215.1.1.0 0.0.0.255 area 20
Router(config-router)#exit
R1
Router(config)#router ospf 33
Router(config-router)#network 200.100.100.32 0.0.0.3 area 0
Router(config-router)#network 200.100.100.64 0.0.0.31 area 0
Router(config-router)#exit
R2
Router(config)#router ospf 2
Router(config-router)#network 200.100.100.32 0.0.0.3 area 0
Router(config-router)#network 200.100.100.128 0.0.0.63 area
0
Router(config-router)#exit
R1
Router(config-router)#network 200.100.100.4 0.0.0.3
Router(config-router)#network 200.100.100.32 0.0.0.15
R2
Router(config-router)#network 200.100.100.4 0.0.0.3
Router(config-router)#network 200.100.100.160 0.0.0.15
Router(config-router)#network 200.100.100.16 0.0.0.3
R3
Router(config-router)#network 200.100.100.16 0.0.0.3
Router(config-router)#network 200.100.100.224 0.0.0.31
Configuring bandwidth on interface
If the actual bandwidth of interface is not equal to
the maximum speed of interface then we have to use bandwidth command to specify the
actual bandwidth.
Router(config)#interface <type> <no>
Router(config-if)#bandwidth <speed>
Configuring logical interface for OSPF
By default the highest IP address of interface will be
elected as Router id. If there is a change in status of interface then router will
reelect some IP as Router id. So if we create logical interface, it will never go down and
first preference give to the logical interface for RID
Command: -
Router(config)#interface loopback <no>
Router(config-if)#ip address 200.100.100.1 255.255.255.0
Router(config-if)#no sh
Router(config-if)#exit
Command to display OSPF parameter
Router#show ip protocol
Router#show ip ospf
Router#show ip ospf neighbor
Router#show ip ospf database
(it shows RID of router)
Router#show ip ospf interfaces
Posted in: CCNA
