IP Routing Static Routing

Information management 2 Groep T Leuven – Information department 2/14 The Router Router Interface is a physical connector that enables a router to send or receive packets Each interface connects to a separate network Consist of socket or jack found on the outside of a router Types of router interfaces: –-Ethernet –-Fastethernet –-Serial –-DSL –-ISDN –-Cable

Information management 3 Groep T Leuven – Information department 3/14 Routing Table Routing table should contain at least 2 items –Destination address –Pointer to the destination Network is missing !

Information management 4 Groep T Leuven – Information department 4/14 Routing Table Router3#show 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, ia - IS-IS inter area * - candidate default, U - per-user static route, o - ODR P - periodic downloaded static route Gateway of last resort is not set /24 is subnetted, 7 subnets S [1/0] via S [1/0] via S [1/0] via C is directly connected, Serial2/0 C is directly connected, FastEthernet0/0 C is directly connected, Serial3/0 S [1/0] via Router3#

Information management 5 Groep T Leuven – Information department 5/14 Routing order 1.Check for a connected network 2.Search for a matching host route 3.Search for a matching network route 4.Search for a default gateway (last resort)

Information management 6 Groep T Leuven – Information department 6/14 The router As a packet travels from one networking device to another –-The Source and Destination IP addresses NEVER change –-The Source & Destination MAC addresses CHANGE as packet is forwarded from one router to the next. –-TTL field decrement by one until a value of zero is reached at which point router discards packet (prevents packets from endlessly traversing the network)

Information management 7 Groep T Leuven – Information department 7/14 Router Path – step 1 PC1 Wants to send something to PC 2 here is part of what happens –Step 1 - PC1 encapsulates packet into a frame. Frame contains R1’s destination MAC address

Information management 8 Groep T Leuven – Information department 8/14 Router Path – step 2 Step 2 - R1 receives Ethernet frame.

Information management 9 Groep T Leuven – Information department 9/14 Router Path – step 2 –Step 2 - R1 receives Ethernet frame.  R1 sees that destination MAC address matches its own MAC.  R1 then strips off Ethernet frame.  R1 Examines destination IP.  R1 consults routing table looking for destination IP.  After finding destination IP in routing table, R1 now looks up next hop IP address.  R1 re-encapsulates IP packet with a new Ethernet frame.  R1 forwards Ethernet packet out Fa0/1 interface.

Information management 10 Groep T Leuven – Information department 10/14 Router Path – step 3 Step 3 - Packet arrives at R2  R2 receives Ethernet frame  R2 sees that destination MAC address matches its own MAC  R2 then strips off Ethernet frame  R2 Examines destination IP  R2 consults routing table looking for destination IP  After finding destination IP in routing table, R2 now looks up next hop IP address  R2 re-encapsulates IP packet with a new data link frame  R2 forwards Ethernet packet out S0/0 interface

Information management 11 Groep T Leuven – Information department 11/14 Router Path – step 4 Step 4 - Packet arrives at R3  R3 receives PPP frame  R3 then strips off PPP frame  R3 Examines destination IP  R3 consults routing table looking for destination IP  After finding destination IP in routing table, R3 is directly connected to destination via its fast Ethernet interface  R3 re-encapsulates IP packet with a new Ethernet frame  R3 forwards Ethernet packet out Fa0/0 interface Step 5 - IP packet arrives at PC2.  Frame is decapsulated & processed by upper layer protocols.

Information management 12 Groep T Leuven – Information department 12/14 Demo – packet tracer

Information management 13 Groep T Leuven – Information department 13/14 Case studies Summary routes Default routes Alternative routes Floating static Load sharing Trouble shooting static routes

Information management 14 Groep T Leuven – Information department 14/14 Exercise Configure the routing that all traffic goes clock wise / / / / / / /24 64 kbps 128 kbps 16 kbps