CISCO NETWORKING ACADEMY Chabot College ELEC IP Routing Protocol Highlights

CISCO NETWORKING ACADEMY IP Routing Protocol Topics Routing tables How routes are learned Default routes Metrics Administrative Distance Distance Vector / Link State RIP / IGRP Commands

CISCO NETWORKING ACADEMY Routing Table Stored in RAM Basis for all path selection decisions Includes destination network address - next hop pairs

CISCO NETWORKING ACADEMY Routing Table Example hayward#show ip route Codes: C - connected, S - static, I - IGRP, R - RIP D - EIGRP, EX - EIGRP external, O - OSPF N1 - OSPF NSSA external type 1, N2 - OSPF NSSA E1 - OSPF external type 1, E2 - OSPF external type 2 i - IS-IS, L1 - IS-IS level-1, * - candidate default Gateway of last resort is not set R /24 [120/1] via , 00:00:07, Serial /16 is subnetted, 3 subnets C is directly connected, Serial1 C is directly connected, Serial0 R [120/1] via , 00:00:10, Serial1 R /24 [120/2] via , 00:00:10, Serial1 S /24 [1/0] via C /24 is directly connected, Ethernet0

CISCO NETWORKING ACADEMY Routing Table Example hayward#show ip route R /24 [120/1] via , 00:00:07, Serial /16 is subnetted, 3 subnets C is directly connected, Serial1 C is directly connected, Serial0 R [120/1] via , 00:00:10, Serial1 R /24 [120/2] via , 00:00:10, Serial1 S /24 [1/0] via C /24 is directly connected, Ethernet0 Destination Network Address Next Hop

CISCO NETWORKING ACADEMY How routes are learned 1. Interface configuration in the config file. Defines directly connected networks even when no dynamic routing is configured: hayward#show ip route /16 is subnetted C is directly connected, Serial1 C is directly connected, Serial0 C /24 is directly connected, Ethernet0

CISCO NETWORKING ACADEMY How routes are learned When dynamic routing is running, directly connected networks are listed in the routing table along with others: hayward#show ip route R /24 [120/1] via , 00:00:07, Serial /16 is subnetted, 3 subnets C is directly connected, Serial1 C is directly connected, Serial0 R [120/1] via , 00:00:10, Serial1 R /24 [120/2] via , 00:00:10, Serial1 S /24 [1/0] via C /24 is directly connected, Ethernet0

CISCO NETWORKING ACADEMY How routes are learned 2. Static routes entered manually in the router config file. hayward#show ip route R /24 [120/1] via , 00:00:07, Serial /16 is subnetted, 3 subnets C is directly connected, Serial1 C is directly connected, Serial0 R [120/1] via , 00:00:10, Serial1 R /24 [120/2] via , 00:00:10, Serial1 S /24 [1/0] via C /24 is directly connected, Ethernet0

CISCO NETWORKING ACADEMY How routes are learned 3. Routes learned from a dynamic routing protocol (e.g. RIP, IGRP, OSPF). hayward#show ip route R /24 [120/1] via , 00:00:07, Serial /16 is subnetted, 3 subnets C is directly connected, Serial1 C is directly connected, Serial0 R [120/1] via , 00:00:10, Serial1 R /24 [120/2] via , 00:00:10, Serial1 S /24 [1/0] via C /24 is directly connected, Ethernet0

CISCO NETWORKING ACADEMY How routes are learned 4. Default route set manually. Shown with * Also: gateway of last resort oakland#show ip route Gateway of last resort is to network /16 is subnetted, 2 subnets C is directly connected, Serial1 R [120/1] via , 00:00:18, Serial1 R /24 [120/2] via , 00:00:18, Serial1 S /24 [1/0] via C /24 is directly connected, Ethernet0 R* /0 [1/0] via

CISCO NETWORKING ACADEMY Static Routes - Why? Security –RIP may reveal too much of your network to others. A static route limits what you “show”. Backup routes –A static route can be a backup to be used automatically if a dynamic route goes down Bandwidth conservation –Dynamic routing uses network bandwidth; static routes do not. –Static routes are sufficient for stub networks

CISCO NETWORKING ACADEMY Stub Networks Only one path in & out of the network; no path selection decision: Only one path to this “stub” network Here, there are path selection decisions. Dynamic routing needed. A static route to the stub net will do.

CISCO NETWORKING ACADEMY Default Routes - the Problem For each packet, routing are decisions based on the routing table rules. What happens to a packet if has a destination that is not included in the routing table?

CISCO NETWORKING ACADEMY Default Routes - the Problem What happens to a packet sent to It is dropped because there is no entry for that network in the routing table: oak#show ip route Gateway of last resort is not set R /24 [120/1] via , 00:00:07, Serial /16 is subnetted, 3 subnets C is directly connected, Serial1 C is directly connected, Serial0 R [120/1] via , 00:00:10, Serial1 R /24 [120/2] via , 00:00:10, Serial1 S /24 [1/0] via C /24 is directly connected, Ethernet0

CISCO NETWORKING ACADEMY Default Routes - the Problem But the routing table can’t hold entries for every network, including all those on the Internet! So we need a route for internet traffic - the default. If packet has a destination not on our network, try sending it here Gateway Our Network

CISCO NETWORKING ACADEMY Default Routes - Terms default route (through) default gateway (also known as) gateway of last resort (to) default network

CISCO NETWORKING ACADEMY Metric Specifies the cost of a route Dynamic routing protocol chooses the route with the lowest cost Metrics differ, depending on routing protocol:

CISCO NETWORKING ACADEMY Administrative Distance Specifies the trustworthiness of a route source Lower values = more trustworthy The IOS chooses the route with lowest distance: IOS ignores these routes

CISCO NETWORKING ACADEMY Distance Vector vs Link State Distance Vector –Each router knows: Direction (vector) Distance (hops) –Example. Destination is: out S0 3 hops away –Does not know exact map to destination. 3 hops

CISCO NETWORKING ACADEMY Distance Vector vs Link State Distance Vector –To reach Joe’s office: Go out middle door & pass through 3 buildings. At each building, you’ll be told which door to exit –Which office could be Joe’s? 3

CISCO NETWORKING ACADEMY Distance Vector vs Link State Distance Vector –To reach Joe’s office: Go out middle door & pass through 3 buildings. At each building, you’ll be told which door to exit –Which office could be Joe’s? 3 2

CISCO NETWORKING ACADEMY Distance Vector vs Link State Distance Vector –To reach Joe’s office: Go out middle door & pass through 3 buildings. At each building, you’ll be told which door to exit –Which office could be Joe’s? 3 2 1

CISCO NETWORKING ACADEMY Distance Vector vs Link State Distance Vector –To reach Joe’s office: Go out middle door & pass through 3 buildings. At each building, you’ll be told which door to exit –Which office could be Joe’s?

CISCO NETWORKING ACADEMY Distance Vector vs Link State Distance Vector –To reach Joe’s office: Go out middle door & pass through 3 buildings. At each building, you’ll be told which door to exit –Which office could be Joe’s? Joe

CISCO NETWORKING ACADEMY Distance Vector vs Link State Link State –Each router knows: Overall map of network Shortest path to destination

CISCO NETWORKING ACADEMY Distance Vector vs Link State Link State –To reach Joe’s office: Follow Campus Map. Take shortest path. Joe

CISCO NETWORKING ACADEMY Distance Vector vs Link State Distance Vector Updates (RIP example) –Each router gossips to its direct neighbor. –Gossip is sent every 30 seconds. –Takes time to pass the gossip to the end of the line. –When all routers have received the gossip they are “converged”. Until then, the routers posses conflicting knowledge. A tells B ABCDEF B tells CC tells DD tells EE tells F

CISCO NETWORKING ACADEMY Distance Vector vs Link State Link State –Each router sends information about its links to all other routers. –Changes in network topology trigger these link state advertisements. –Each router then develops a full map of the network. A tells all other routers when it learns of a change in the network ABCDEF When any other router detects a change, it also tells everyone. Down

CISCO NETWORKING ACADEMY RIP Distance-Vector Updates: every 30 seconds Metric: Hops Default administrative distance: 120 Convergence: slow Versions 1 & 2

CISCO NETWORKING ACADEMY IGRP Distance-Vector Updates: every 90 seconds Metric: bandwidth & delay (defaults) Can also include load, reliability Default administrative distance: 100 Convergence: faster than RIP

CISCO NETWORKING ACADEMY Configuring Dynamic Routing 1.Specify the routing protocol. –Ordinarily, all routers must run the same protocol. 2.Specify all directly connected networks on which the router will send and receive route updates (also called advertisements). –Network are specified by major network numbers, not subnets. Example - here the network is : / /16

CISCO NETWORKING ACADEMY Commands Configuring RIP oak(config)#router rip oak(config-router)#network oak(config-router)#network oak(config-router)#^Z Enables RIP routing Sets RIP to send/receive updates on these directly connected networks

CISCO NETWORKING ACADEMY Commands Configuring RIP version 2 - same as RIP but –adds version 2 statement –version should be the same for all routers oak(config)#router rip oak(config-router)#version 2 oak(config-router)#network oak(config-router)#network oak(config-router)#^Z Enables RIP routing Sets RIP version 2

CISCO NETWORKING ACADEMY Commands Configuring IGRP - same as RIP, but –includes an autonomous system number –AS must be same for all routers oak(config)#router igrp 40 oak(config-router)#network oak(config-router)#network oak(config-router)#^Z Enables IGRP routing Autonomous System #

CISCO NETWORKING ACADEMY Commands Configuring a static route - outgoing interface fre(config)#ip route s0 fre(config)#^Z Destination network & mask Route to network via this outgoing interface

CISCO NETWORKING ACADEMY Commands Configuring a static route - next hop fre(config)#ip route s0 fre(config)#ip route fre(config)#^Z Destination network & mask Route to network via this next hop address. Use this format to improve clarity of routing tables.

CISCO NETWORKING ACADEMY Comands Specifying next hop –It is the ip address of nearest interface of the neighbor router along the route. –From Router B, this is the next hop to LAN A: LAN DLAN C LAN A B

CISCO NETWORKING ACADEMY Comands From Router B, what is the next hop to –the net? – Net B Net Net

CISCO NETWORKING ACADEMY Comands From Router B, what is the next hop to –the net? – Net B Net Net –The next hop is always on the neighbor router!

CISCO NETWORKING ACADEMY Comands From Router B, what are the only two possible next hop addreses? – Net B Net Net –

CISCO NETWORKING ACADEMY Commands Static route - administrative distance parameter Optional oak(config)#ip route s0 121 oak(config)#^Z Administrative Distance

CISCO NETWORKING ACADEMY Commands Static route - administrative distance If unspecified, default distance is 0 for outgoing interface format. These routes will show as S but will be listed as directly connected in the routing table. oak(config)#ip route s0

CISCO NETWORKING ACADEMY Commands Static route - administrative distance If unspecified, default distance is 1 for next hop format. These routes will show as S (static) in the routing table. oak(config)#ip route

CISCO NETWORKING ACADEMY Commands Configuring a default route (default network) method 1 - set a default route to the wildcard network & subnet of hay(config)#ip route hay(config)#^Z Wildcard network & mask Route to default network via this “next hop” address - the address of the direct neighbor interface. See

CISCO NETWORKING ACADEMY oakland#show ip route Gateway of last resort is to network /16 is subnetted, 2 subnets C is directly connected, Serial1 R [120/1] via , 00:00:18, Serial1 R /24 [120/2] via , 00:00:18, Serial1 S /24 [1/0] via C /24 is directly connected, Ethernet0 R* /0 [1/0] via Commands method 1 - RIP will automatically redistribute the default route to the wildcard network & subnet of to other routers: Distributed from hayward to oakland by RIP

CISCO NETWORKING ACADEMY Commands Configuring a default route (default network) method 2: (presented in the curriculum) ip default-network xxx.xxx.xxx.xxx hay(config)#ip default-network hay(config)#^Z Send default traffic here See

CISCO NETWORKING ACADEMY Commands Default network must be –defined on each router or –redistributed by RIP to other routers

CISCO NETWORKING ACADEMY Commands Redistribution methods: – : With IOS Version 12.0, RIP automatically distributes a route to to other routers. With IOS Version 12.1 or later, you must add the default-information originate command: hay(config)#router rip hay(config-router)#default-information originate hay(config)#router rip hay(config-router)#redistribute static –ip default-network: To force RIP to redistribute the default route, you must add the redistribute static command:

CISCO NETWORKING ACADEMY Commands show ip route displays routing table oakland#show ip route Gateway of last resort is to network R /24 [120/1] via , 00:00:11, Serial /16 is subnetted, 3 subnets C is directly connected, Serial1 C is directly connected, Serial0 R [120/1] via , 00:00:18, Serial1 R* /24 [120/2] via , 00:00:18, Serial1 S /24 [1/0] via C /24 is directly connected, Ethernet0 Route Source [Administrative Distance/Metric]

CISCO NETWORKING ACADEMY Commands show ip protocols oak(config)#show ip protocols Routing Protocol is "rip" Sending updates every 30 seconds, next due in 2 seconds Invalid after 180 seconds, hold down 180, flushed after 240 Outgoing update filter list for all interfaces is not set Incoming update filter list for all interfaces is not set Redistributing: rip Routing for Networks: Update Distance: (default is 120)

CISCO NETWORKING ACADEMY Commands show ip interfaces interface detail oak(config)#show ip interfaces Ethernet0 is up, line protocol is up Internet address is , subnetmask Broadcast address is Address determined by non-volatile memory MTU is 1500 bytes Helper address is not set Secondary address , subnet mask Directed broadcast forwarding is enabled Outgoing access list is not set Inbound access list is not set Proxy ARP is enabled Split horizon is enabled

CISCO NETWORKING ACADEMY Commands debug ip rip Displays rip updates as they are received & sent by router Temporary troubleshooting only - must not be left on! Turn off with no debug ip rip or no debug all