Chapter 5 IP Routing Objectives Understand the IP routing process Create and verify static routing Create and verify default routing Resolve network loops in distancevector routing Configure and verify RIP routing Configure and verify IGRP routing Routing Definition Process of moving packets from one network to another and delivering packets to hosts What routers need to know Destination address Neighboring routers Possible routes to all networks Administrator Other routers Best route How to maintain and verify routing info Routing Knows about directly connected networks Dynamic routing Must be told about all other networks Process of a router learning about another networks from neighboring routers Routing protocols determine how this is done Static routing Administrator manually configures routing tables IP Routing Process IP Routing Process cont IP Routing in a Larger Network Assigning IP Addresses ip address ip address subnet mask int fa0 0 ip address 172 16 20 1 255 255 255 0 no shutdown 2621A Configuration Router en Router config t Router config hostname 2621A 2621A config interface fa0 0 2621A config if ip address 172 16 10 1 255 255 255 0 2621A config if no shut IP Routing in Networks Routing tables Configuration Required because all networks are not directly connected Types of routing Static Default Dynamic Static Routing Definition Benefits No overhead Security Disadvantage Administrator manually adds Network Changes Large networks Verify using Ping test up to Internet Layer IP Telnet test up to Host to Host layer TCP Adding a Static Route ip route destination network mask next hop address or exitinterface administrative distance permanent Exit interface Must be used if destined for point to point connection ie WAN Next hop address If used must be up ie You can ping it If down the route will show up in config but not in the routing table Administrative Distance default 1 page 224 Permanent Will not discard if interface down or unable to communicate with next hop Must use next hop address 2621A 2501A Router en Router config t 2621A config ip route 172 16 20 0 255 255 255 0 172 16 10 2 2621A config ip route 172 16 30 0 255 255 255 0 172 16 10 2 2621A config ip route 172 16 40 0 255 255 255 0 172 16 10 2 2621A config ip route 172 16 50 0 255 255 255 0 172 16 10 2 2501A en 2501A config t 2501A config ip route 172 16 30 0 255 255 255 0 s0 2501A config ip route 172 16 40 0 255 255 255 0 s0 2501A config ip route 172 16 50 0 255 255 255 0 s0 2621A Routing Table 2612A sh ip route Codes C connected S static I IGRP R RIP M mobile B BGP D EIGRP EX EIGRP external O OSPF IA OSPF inter area N1 OSPF NSSA external type 1 N2 OSPF NSSA external type 2 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 o ODR Gateway of last resort is not set 172 16 0 0 24 is subnetted 6 subnets S S S S C C 172 16 50 0 172 16 40 0 172 16 30 0 172 16 20 0 172 16 11 0 172 16 10 0 1 0 via 172 16 10 2 1 0 via 172 16 10 2 1 0 via 172 16 10 2 1 0 via 172 16 10 2 is directly connected FastEthernet0 0 is directly connected FastEthernet0 1 Deleting a Route No ip route destination network mask next hop address or exitinterface administrative distance permanent 2621A config no ip route 172 16 20 0 255 255 255 0 172 16 10 2 2621A config no ip route 172 16 30 0 255 255 255 0 172 16 10 2 2621A config no ip route 172 16 40 0 255 255 255 0 172 16 10 2 2621A config no ip route 172 16 50 0 255 255 255 0 172 16 10 2 No way to entire delete routing table 2621A Routing Table 2612A sh ip route Codes C connected S static I IGRP R RIP M mobile B BGP D EIGRP EX EIGRP external O OSPF IA OSPF inter area N1 OSPF NSSA external type 1 N2 OSPF NSSA external type 2 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 o ODR Gateway of last resort is not set 172 16 0 0 24 is subnetted 2 subnets C C 172 16 11 0 is directly connected FastEthernet0 0 172 16 10 0 is directly connected FastEthernet0 1 Default Routing Definition Can only use on stub networks Send to a remote destination not in the routing table Routers with only one interface connected to internetwork Configuration Uses wildcards for network address and subnet mask ip route 0 0 0 0 0 0 0 0 ip address of next hop Stub Networks Stub network IP Routing Classful Subnet mask must be present All Cisco routers default Classless Used with default routing because no subnet mask is available Router must be told to use classes routing 2501C ip classless Default Routing Configuration Example 2501C config no ip route 172 16 10 0 255 255 255 0 172 16 40 1 2501C config no ip route 172 16 20 0 255 255 255 0 172 16 40 1 2501C config no ip route 172 16 30 0 255 255 255 0 172 16 40 1 2501C config ip route 0 0 0 0 0 0 0 0 172 16 40 1 2501C config ip classless Verifying Ping Traceroute Telnet Finding neighboring interfaces ip address 2501B sh cdp entry Device ID Router Entry address es IP address 172 16 40 2 Interface Serial1 Port ID outgoing port Serial0 Holdtime 175 sec Device ID Entry address es IP address 172 16 20 1 Interface Serial0 Port ID outgoing port Serial0 Holdtime 130 sec 2501B Our Network Dynamic Routing Definition Process of using routing protocols to find and update routing information Types of Routing Protocols Interior Gateway Protocol IGP Used within AS Exterior Gateway Protocol EGP Used between AS s IGP vs EGP Administrative Distances Classes of Routing Protocols Classes Distance Vector Each time a packet goes through a router hop Best route one with the least hops RIP IGRP Link State Three tables Directly attached neighbors Entire network topology Routing table OSPF Hybrid Uses the best of both EIGRP Distance Vector Routing Protocols Pinhole Hop Congestion count equal therefore both routes seen as equal Distance Vector Routing Start up No data forwarded while routers are converging Routing Loops Stopping Routing Loops Maximum Hop Count Split Horizon Can not send route info out the interface it learned it from Route Poisoning Loops cause a counting to infinity problem Maximum hop count 15 16 makes next hop unreachable Route hop set to 16 Neighboring routers respond with a poison reverse Holddowns Prevents routes from changing to rapidly …