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•To route, a router needs to do the following:• Know the destination address• Identify the sources it can learn from• Discover possible routes• Select the best route• Maintain and verify routing information
What Is Routing?
• Static Route– Uses a route that a
network administrator enters into the router manually
•Dynamic Route–Uses a route that a
network routing protocol adjusts automatically for topology or traffic changes
Identifying Static and Dynamic Routes
Static Routes
• Configure unidirectional static routes to and from a stub network to allow communications to occur.
– Defines a path to an IP destination network or subnet or host
Router(config)#ip route network [mask] {address | interface}[distance] [permanent]
Static Route Configuration
Static Route Example
• This is a unidirectional route. You must have a route configured in the opposite direction.
Verifying the Static Route Configuration
router#show ip routeCodes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default U - per-user static route Gateway of last resort is 0.0.0.0 to network 0.0.0.0 10.0.0.0/8 is subnetted, 1 subnetsC 10.1.1.0 is directly connected, Serial0S* 0.0.0.0/0 is directly connected, Serial0
• Routing protocols are used between routers to determine paths and maintain routing tables.
• Once the path is determined, a router can route a routed protocol (IP).
What Is a Routing Protocol?
• An autonomous system is a collection of networks under a common administrative domain.
• IGPs operate within an autonomous system.
• EGPs connect different autonomous systems.
Autonomous Systems: Interior or Exterior Routing Protocols
• Routers pass periodic copies of routing table to neighbor routers and accumulate distance vectors.
Distance Vector Routing Protocols
Metric
• Is a value that assign to each path
• Use to calculate with path is the best path to remote destination network
• Different in routing protocol
• The route with the lowest metric is the best route
– Maximum is 6 paths (default = 4)– Hop-count metric selects the path– Routes update every 30 seconds
RIP Overview
Load Balancing with RIP
By default, on a Cisco router, if multiple equal-cost paths existup to six entries are placed into the forwarding database and the routersload balance between them.
– Defines an IP routing protocol
Router(config)#router protocol [keyword]
• Mandatory configuration command for each IP routing process
• Identifies the physically connected network that routing updates are forwarded to
Router(config-router)#network network-number
Dynamic Routing Configuration
– Starts the RIP routing process
Router(config)#router rip
Router(config-router)#network network-number
• Selects participating attached networks
• Requires a major classful network number
RIP Configuration
Summary– RIP is a distance vector routing protocol that uses hop
count as the metric for route selection and broadcasts routing updates every 30 seconds.
– To enable a dynamic routing protocol, you will select the routing protocol and then assign IP network numbers.
– The router rip command specifies RIP as the routing protocol. The network command identifies a participating attached network.
– The show ip commands display information about routing protocols and the routing table.
– Use the debug ip rip command to display information on RIP routing transactions.
S0 : 192.168.1.1
S1 : 192.168.3.1
F0/0 : 192.168.2.1
S0 : 192.168.3.2
S1 : 192.168.4.1
S0 : 192.168.4.2
S0 : 192.168.9.2
S0 : 192.168.7.2
S1 : 192.168.7.1S1 : 192.168.9.1
S1 : 192.168.1.2
F0/0 : 192.168.10.1
F0/0 : 192.168.5.1 F0/0 : 192.168.6.1 F0/0 : 192.168.8.1
Configure RIP
1. Assign ip to interface
2. Configure RIP Routing
3. Ping
4. Trace route
5. Show routing table
Key Elements of RIP
– Hop count is the metric for path selection.– Maximum hop count of 15– 16 hops is considered infinity– By default, routing updates are broadcast
every 30 seconds.– Capable of load balancing
• This is helpful in larger networks and solves the problem of 15 hops being the maximum possible in a RIP network
Delay of line
amount of time necessary to move a packet transmition from source to destination.
1 mb/s 1 mb/s
2 mb/s2 mb/s
MTU
• MTU : Maximum Transmission Unit
-The Maximum Packet size, in byte , that a particular interface can handle.
- The default MTU value on Ethernet interface is 1500 byte.
IGRP metric calculation
• By default IGRP chooses a route based on
Bandwidth and delay
Metric = bandwidth + delay
–Maximum 6 paths (default = 4)
–Within metric variance
–Next-hop router closer to destination
IGRP Unequal Multiple Paths
Configuring IGRP
Router(config-router)#network network-number
• Selects participating attached networks
Router(config)#router igrp autonomous-system
• Defines IGRP as the IP routing protocol
debug ip igrp events Command
RouterA#debug ip igrp eventsIGRP event debugging is onRouterA#00:23:44: IGRP: sending update to 255.255.255.255 via Ethernet0 (172.16.1.1)00:23:44: IGRP: Update contains 0 interior, 2 system, and 0 exterior routes.00:23:44: IGRP: Total routes in update: 200:23:44: IGRP: sending update to 255.255.255.255 via Serial2 (10.1.1.1)00:23:45: IGRP: Update contains 0 interior, 1 system, and 0 exterior routes.00:23:45: IGRP: Total routes in update: 100:23:48: IGRP: received update from 10.1.1.2 on Serial200:23:48: IGRP: Update contains 1 interior, 1 system, and 0 exterior routes.00:23:48: IGRP: Total routes in update: 2
S0 : 192.168.1.1
S1 : 192.168.3.1
F0/0 : 192.168.2.1
S0 : 192.168.3.2
S1 : 192.168.4.1
S0 : 192.168.4.2
S0 : 192.168.9.2
S0 : 192.168.7.2
S1 : 192.168.7.1S1 : 192.168.9.1
S1 : 192.168.1.2
F0/0 : 192.168.10.1
F0/0 : 192.168.5.1 F0/0 : 192.168.6.1 F0/0 : 192.168.8.1
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