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Inside the Router Routers are computers Router CPU and Memory Internetwork Operating System Router Bootup Process Router Ports and Interfaces Routers and the Network Layer Note Almost everything in this chapter will be covered in more detail in later chapters. This course is about understanding and to be able to analyze/troubleshoot networks, not how to type in a command. Example: show ip route Type in the command (easy) Explain what the output is displaying (more understanding) Analyze why you are seeing this information but also know if there is anything missing or if there is something you shouldn’t be seeing. That is what this course is about! 2 Characteristics of a Network Network Characteristics and Attributes 4 Topology Physical Topology: Is the arrangement of the cables, network devices, and end systems. It describes how the network devices are actually interconnected with wires and cables. Logical Topology: Is the path over which the data is transferred in a network. It describes how the network devices appear connected to network users. 5 Network Characteristics and Attributes Speed: The measure of the data rate in bits per second (b/s) of a given link. Cost: Indicates the general expense for purchasing of network components, and installation and maintenance of the network. Security: Indicates how protected the network is, including the information that is transmitted over the network. 6 Network Characteristics and Attributes Availability: Is a measure of the probability that the network is available for use when it is required. Scalability: Indicates how easily the network can accommodate more users and data transmission requirements. Reliability: Indicates the dependability of the components that make up the network, such as the routers, switches, PCs, and servers. Often measured as a probability of failure or as the mean time between failures (MTBF). 7 Routers Why Routing? The router is responsible for the routing of traffic between networks. 9 What is a Router? Leonard Kleinrock and the first IMP. A router is a specialized computer! It sends packets over the data network. It is responsible for interconnecting networks by selecting the best path for a packet to travel and forwarding packets to their destination The first router (ARPANET): IMP (Interface Message Processor) Honeywell 516 minicomputer August 30, 1969 10 Router Components Regardless of their function, size or complexity, all router models are essentially computers and require: Operating systems (OS) Central processing units (CPU) Random-access memory (RAM) Read-only memory (ROM) Routers also have special memory that includes Flash and nonvolatile random-access memory (NVRAM). 11 Router Memory Memory Volatile / Non-Volatile Volatile • • • • Running IOS Running configuration file IP routing and ARP tables Packet buffer Non-Volatile • • • Bootup instructions Basic diagnostic software Limited IOS Non-Volatile • Startup configuration file Non-Volatile • • IOS Other system files RAM (Random Access Memory) ROM (Read-Only Memory) NVRAM (Non-Volatile RAM) Flash Stores 12 Router Backplane Double-wide eHWIC slots eHWIC 0 AUX port LAN interfaces The backplane of a router includes: Console RJ45 Two 4 GB flash card slots Console USB Type B USB Ports 13 Routers vs Multilayer Switches Routers and multilayer switches both perform routing (connecting networks) Routers may have different types of interfaces (Ethernet, serial, ATM, etc.) while multilayer switches will only have Ethernet interfaces. While routers can be used to segment LAN devices, their major use is as WAN devices. Each devices does have its own advantages. Routers are: The backbone devices of large intranets and of the Internet They operate at Layer 3 (network layer) of the OSI model They make decisions based on network addresses (IPv4, IPv6). 14 Routers in LANs and WANs Routers can connect multiple networks. Routers have multiple interfaces, each on a different IP network. 15 Best Path Decisions The primary responsibility of a router is to direct packets by: Determining the best path to send packets Forwarding packets toward their destination 16 Best Path Decisions Routers use routing tables to determine the best path to send packets. Routers encapsulate the packet and forward it to the interface indicated in routing table. 17 Router Functions Routing tables can be created: Manually with static routes Dynamically with routing protocols Routing protocols exchanges network topology (path) information with other routers. 18 Best Path Decisions The router uses its routing table to determine the best path to forward the packet. When the router receives a packet, it examines its destination IP address and searches for the best network address match in the routing table. The routing table entries also includes the interface to be used to forward the packet. Once a match is found, the router encapsulates the IP packet into the data link frame of the outgoing or exit interface. The packet is then forwarded toward its destination. Routers support three packet-forwarding mechanisms: Process switching Fast Switching Cisco Express Forwarding (CEF) 19 Analogy: Process switching solves a problem by doing math long hand, even if it is the identical problem. Process Switching Control Plane IP Routing Table CPU Ingress Interface 1st Packet Data Plane Egress Interface 2nd Packet 3rd Packet 4th Packet 5th Packet Earliest switching method. (Applies to both routers and multilayer switches.) This is an older packet forwarding mechanism. When a packet arrives on an interface, it is forwarded to the control plane where the CPU examines the routing table, determines the exit interface and forwards the packet. It does this for every packet, even if the destination is the same for a stream of packets. 20 Fast Switching Analogy: Fast switching solves a problem by doing math long hand one time and remembering the answer for subsequent identical problems. Control Plane IP Routing Table CPU Ingress Interface Data Plane 1st Packet 2nd Packet 3rd Packet 4th Packet 5th Packet Egress Interface Fast Forward Cache As routers had to process more packets, it was determined process switching was not fast enough. Next evolution in packet switching was Fast Switching. (Applies to both routers and multilayer switches.) The first packet is process-switched (CPU + routing table) but it also uses a fast-switching cache to store next-hop information of the flow. The next packets in the flow are forwarded using the cache and 21 without CPU intervention. Analogy: CEF solves every possible problem ahead of time in a spreadsheet. CEF Switching Control Plane CPU Ingress Interface 1st Packet 2nd Packet 3rd Packet 4th Packet 5th Packet Data Plane Egress Interface FIB and Adjacency Table Preferred and default Cisco IOS packet-forwarding mechanism for routers and multilayer switches. CEF copies the routing table to the Forwarding Information Base (FIB) CEF creates an adjacency table which contains all the layer 2 information a router would have to consider when forwarding a packet such as Ethernet destination MAC address. The adjacency table is created from the ARP table. CEF is discussed in more detail in CIS 187 CCNP SWITCH. 22 Connect Devices Home Office Devices Connect … Laptops and tablets connect wirelessly to a home router. A network printer connects using an Ethernet cable to the switch port on the home router. The home router connects to the service provider cable modem using an Ethernet cable. The cable modem connects to the Internet service provider (ISP) network. 24 Branch Site Devices Connect … • Corporate resources (i.e., file servers and printers) connect to Layer 2 switches. • PCs and VoIP phones connect to Layer 2 Ethernet switches. • Laptops and smartphones connect wirelessly to WAPs. • WAPs connect to switches. • Layer 2 switches connect to the edge router. • The edge router connects to a WAN service provider (SP) and an ISP for backup purposes. 25 Central Site Devices Connect … • PCs and VoIP phones connect to Layer 2 Ethernet switches. • Layer 2 switches connect to Layer 3 switches using Ethernet fiber-optic cables. • Layer 3 switches connect to the edge router. • The corporate website server is connected to the edge router interface. • The edge router connects to a WAN SP and an ISP for backup purposes. 26 Default Gateways To enable network access, devices must be configured with IP address information to identify the appropriate: IP address - Identifies a unique host on a local network. Subnet mask - Identifies with which network subnet the host can communicate. Default gateway - Identifies the router to send a packet to when the destination is not on the same local network subnet. 27 Documenting a Network Network documentation should identify: Device names Interfaces used in the design IP addresses and subnet masks Default gateway addresses Useful documents include: Network topology diagram Addressing Table 28 Documenting a Network 192.168.1.0/24 192.168.2.0/24 .1 .10 .1 192.168.3.0/24 .2 .1 .10 29 Hosts Addressing A host can be assigned IP address information either: Statically - The host is manually assigned the correct IP address, subnet mask, and default gateway. The DNS server IP address can also be configured. Dynamically - IP address information is provided by a server using the Dynamic Host Configuration Protocol (DHCP). The DHCP server provides a valid IP address, subnet mask, and default gateway for end devices. Other information may be provided by the server. 30 Device LEDs Most network interfaces have one or two LED link indicators next to the interface. Generally: Green LED means a good connection Blinking green LED indicates network activity. No light then there may be a problem with either the network cable or the network itself. The switch port where the connection terminates would also have an LED indicator lit. If one or both ends are not lit, try a different network cable. 31 Cisco 1941 LEDs 32 Console Connection SSH Console Connection In a production environment, infrastructure devices are commonly accessed remotely using Secure Shell (SSH) or HyperText Transfer Protocol Secure (HTTPS). Console access is really only required when initially configuring a device, if remote access fails, or if the change may affect the remote access. Console access requires: Console cable – RJ-45-to-DB-9 console cable Terminal emulation software – Tera Term, PuTTY, HyperTerminal 33 USB Serial Console Connection The Cisco ISR G2 supports a USB serial console connection. To establish connectivity, a USB Type-A to USB Type-B (mini-B USB) is required, as well as an operating system device driver. This device driver is available from http://www.cisco.com. Although these routers have two console ports, only one console port can be active at a time. When a cable is plugged into the USB console port, the RJ-45 port becomes inactive. When the USB cable is removed from the USB port, the RJ-45 port becomes active. 34 Console Connection Requirements Port on Computer Serial port Cable required Port on ISR • RJ45-to-DB9 console cable RJ45 Console port USB Type-A port Terminal emulation • USB-to-RS232 compatible serial port adapter • Adapter may require a software driver • RJ45-to-DB9 console cable • USB Type-A to USB Type-B (mini-B USB) • An device driver is required and available from cisco.com. USB Type-B (mini-B USB) Tera Term PuTTY 35 Console Connection Requirements Port on Computer Cable required Port on ISR Terminal emulation Serial port RJ45 Console port Tera Term USB Type-A port • USB Type-A to USB Type-B (mini-B USB) • An device driver is required and available from cisco.com. USB Type-B (mini-B USB) PuTTY 36 Configuring Routers Name the Device .2 .2 Router# configure terminal Enter configuration commands, one per line. Router(config)# hostname R1 R1(config)# End with CNTL/Z. 38 Secure Management Access .2 .2 R1(config)# enable secret class R1(config)# username admin secret class R1(config)# line console 0 R1(config-line)# password cisco R1(config-line)# login R1(config-line)# exit R1(config)# ip domain-name cisco.com R1(config)# crypto key generate rsa 1024 R1(config)# line vty 0 4 R1(config-line)# transport input ssh R1(config-line)# login local R1(config-line)# exit R1(config)# service password-encryption R1(config)# 39 Configure a Banner .2 .2 R1(config)# banner motd $ Authorized Access Only! $ R1(config)# 40 Save the Configuration .2 .2 R1# copy running-config startup-config Destination filename [startup-config]? Building configuration... [OK] R1# 41 Configure Basic Settings on R2 Router# configure terminal Enter configuration commands, one per line. End with CNTL/Z. R2(config)# enable secret class R2(config)# username admin secret class R2(config)# line console 0 R2(config-line)# password cisco R2(config-line)# login R2(config-line)# exit R2(config)# ip domain-name cisco.com R2(config)# crypto key generate rsa 1024 R2(config)# line vty 0 4 R2(config-line)# transport input ssh R2(config-line)# login local R2(config-line)# exit R2(config)# R2(config)# service password-encryption R2(config)# R2(config)# banner motd $ Authorized Access Only! $ R2(config)# end R2# copy running-config startup-config Destination filename [startup-config]? Building configuration... [OK] R2# 42 Configure the Gi0/0 Interface .2 .2 R1(config)# interface gigabitethernet 0/0 R1(config-if)# description Link to LAN 1 R1(config-if)# ip address 192.168.10.1 255.255.255.0 R1(config-if)# no shutdown R1(config-if)# exit R1(config)# *Jan 30 22:04:47.551: %LINK-3-UPDOWN: Interface GigabitEthernet0/0, changed state to down R1(config)# *Jan 30 22:04:50.899: %LINK-3-UPDOWN: Interface GigabitEthernet0/0, changed state to up *Jan 30 22:04:51.899: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0, changed state to up R1(config)# 43 Configure the Gi0/1 Interface .2 .2 R1(config)# interface gigabitethernet 0/1 R1(config-if)# description Link to LAN 2 R1(config-if)# ip address 192.168.11.1 255.255.255.0 R1(config-if)# no shutdown R1(config-if)# exit *Jan 30 22:06:02.543: %LINK-3-UPDOWN: Interface GigabitEthernet0/1, changed state to down R1(config)# *Jan 30 22:06:05.899: %LINK-3-UPDOWN: Interface GigabitEthernet0/1, changed state to up *Jan 30 22:06:06.899: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to up R1(config)# 44 Configure the S0/0/0 Interface .2 .2 R1(config)# interface serial 0/0/0 R1(config-if)# description Link to R2 R1(config-if)# ip address 209.165.200.225 255.255.255.252 R1(config-if)# clockrate 128000 R1(config-if)# no shutdown R1(config-if)# exit *Jan 30 23:01:17.323: %LINK-3-UPDOWN: Interface Serial0/0/0, changed state to down R1(config)# 45 Configure the R2 Interfaces R2(config)#interface gigabitethernet 0/0 R2(config-if)#description Link to LAN 3 R2(config-if)#ip address 10.1.1.1 255.255.255.0 R2(config-if)#no shutdown R2(config-if)#exit *Jan 30 23:08:34.139: Output omitted R2(config)# R2(config)#interface gigabitethernet 0/1 R2(config-if)#description Link to LAN 4 R2(config-if)#ip address 10.1.2.1 255.255.255.0 R2(config-if)#no shutdown R2(config-if)#exit *Jan 30 23:09:56.915: Output omitted R2(config)# R2(config)#interface serial 0/0/0 R2(config-if)#description Link to R1 R2(config-if)#ip address 209.165.200.226 255.255.255.252 R2(config-if)#no shutdown R2(config-if)#exit *Jan 30 23:09:18.451: %LINK-3-UPDOWN: Interface Serial0/0/0, changed state to up *Jan 30 23:09:19.451: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0/0, changed state to up R2(config)# R1’s Serial 0/0/0 interface will also now be in the up state 46 Statically Assign IPv6 Address to Host 2001:0DB8:ACAD:1::/64 PC1 PC2 :10 :10 2001:0DB8:ACAD:3::/64 G0/0 :1 :1 G0/1 R1 :1 S0/0/0 2001:0DB8:ACAD:2::/64 47 Configuring IPv6 Address on Gi0/0 2001:0DB8:ACAD:1::/64 PC1 PC2 :10 :10 2001:0DB8:ACAD:3::/64 G0/0 :1 :1 G0/1 R1 :1 S0/0/0 2001:0DB8:ACAD:2::/64 R1(config)# interface gigabitethernet 0/0 R1(config-if)# description Link to LAN 1 R1(config-if)# ipv6 address 2001:db8:acad:1::1/64 R1(config-if)# no shutdown R1(config-if)# exit R1(config)# *Feb 3 21:38:37.279: %LINK-3-UPDOWN: Interface GigabitEthernet0/0, changed state to down *Feb 3 21:38:40.967: %LINK-3-UPDOWN: Interface GigabitEthernet0/0, changed state to up *Feb 3 21:38:41.967: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0, changed state to up R1(config)# 48 Configuring IPv6 Address on Gi0/1 2001:0DB8:ACAD:1::/64 PC1 PC2 :10 :10 2001:0DB8:ACAD:3::/64 G0/0 :1 :1 G0/1 R1 :1 S0/0/0 2001:0DB8:ACAD:2::/64 R1(config)# interface gigabitethernet 0/1 R1(config-if)# description Link to LAN 2 R1(config-if)# ipv6 address 2001:db8:acad:2::1/64 R1(config-if)# no shutdown R1(config-if)# exit R1(config)# *Feb 3 21:39:21.867: %LINK-3-UPDOWN: Interface GigabitEthernet0/1, changed state to down *Feb 3 21:39:24.967: %LINK-3-UPDOWN: Interface GigabitEthernet0/1, changed state to up *Feb 3 21:39:25.967: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to up R1(config)# 49 Configuring IPv6 Address on S0/0/0 2001:0DB8:ACAD:1::/64 PC1 PC2 :10 :10 2001:0DB8:ACAD:3::/64 G0/0 :1 :1 G0/1 R1 :1 S0/0/0 2001:0DB8:ACAD:2::/64 R1(config)# interface serial 0/0/0 R1(config-if)# description Link to R2 R1(config-if)# ipv6 address 2001:db8:acad:3::1/64 R1(config-if)# clock rate 128000 R1(config-if)# no shutdown R1(config-if)# *Feb 3 21:39:43.307: %LINK-3-UPDOWN: Interface Serial0/0/0, changed state to down R1(config-if)# 50 Configuring the R2 Interfaces 2001:0DB8:ACAD:0003::/64 :2 S0/0/0 2001:0DB8:ACAD:0004::/64 :10 G0/0 :1 R2 G0/1 :1 .:10 2001:0DB8:ACAD:0005::/64 R2(config)#interface gigabitethernet 0/0 R2(config-if)#description Link to LAN 3 R2(config-if)#ipv6 address 2001:db8:acad:4::1/64 R2(config-if)#no shutdown R2(config-if)#exit R2(config)#interface gigabitethernet 0/1 R2(config-if)#description Link to LAN 4 R2(config-if)#ipv6 address 2001:db8:acad:5::1/64 R2(config-if)#no shutdown R2(config-if)#exit R2(config)#interface serial 0/0/0 R2(config-if)#description Link to R1 R2(config-if)#ipv6 address 2001:db8:acad:3::2/64 R2(config-if)#no shutdown 51 Verify Summary Interface Status .2 .2 R1# show ip interface brief Interface IP-Address OK? Method Status Protocol Embedded-Service-Engine0/0 unassigned YES unset administratively down GigabitEthernet0/0 192.168.10.1 YES manual up GigabitEthernet0/1 192.168.11.1 YES manual up Serial0/0/0 209.165.200.225 YES manual up Serial0/0/1 unassigned YES unset administratively down down down up up up R1# 52 Verify Routing Table .2 .2 R1# show ip route Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP <output omitted. Gateway of last resort is not set C L C L C L R1# 192.168.10.0/24 is variably subnetted, 2 subnets, 2 masks 192.168.10.0/24 is directly connected, GigabitEthernet0/0 Network Address 192.168.10.1/32 is directly connected, GigabitEthernet0/0 Interface Address 192.168.11.0/24 is variably subnetted, 2 subnets, 2 masks 192.168.11.0/24 is directly connected, GigabitEthernet0/1 Network Address 192.168.11.1/32 is directly connected, GigabitEthernet0/1 Interface Address 209.165.200.0/24 is variably subnetted, 2 subnets, 2 masks 209.165.200.224/30 is directly connected, Serial0/0/0 Network Address 209.165.200.225/32 is directly connected, Serial0/0/0 Interface Address 53 Verify Interface Configuration .2 .2 R1# show running-config interface gigabitEthernet 0/0 Building configuration... Current configuration : 128 bytes ! interface GigabitEthernet0/0 description Link to LAN 1 ip address 192.168.10.1 255.255.255.0 duplex auto speed auto end R1# 54 Verifying the R1 Gi0/0 Interface R1#show interfaces gigabitEthernet 0/0 GigabitEthernet0/0 is up, line protocol is up Hardware is CN Gigabit Ethernet, address is fc99.4775.c3e0 (bia fc99.4775.c3e0) Description: Link to LAN 1 Internet address is 192.168.10.1/24 MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation ARPA, loopback not set Keepalive set (10 sec) Full Duplex, 100Mbps, media type is RJ45 output flow-control is unsupported, input flow-control is unsupported ARP type: ARPA, ARP Timeout 04:00:00 Last input 00:05:21, output 00:00:00, output hang never Last clearing of "show interface" counters never Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0 Queueing strategy: fifo Output queue: 0/40 (size/max) 5 minute input rate 0 bits/sec, 0 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec 329 packets input, 70930 bytes, 0 no buffer Received 298 broadcasts (0 IP multicasts) 0 runts, 0 giants, 0 throttles 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored 0 watchdog, 0 multicast, 0 pause input 437 packets output, 47524 bytes, 0 underruns 0 output errors, 0 collisions, 1 interface resets 30 unknown protocol drops 0 babbles, 0 late collision, 0 deferred 0 lost carrier, 0 no carrier, 0 pause output 0 output buffer failures, 0 output buffers swapped out R1# 55 Verify the R1 Gi0/1 Interface R1# show interfaces gigabitEthernet 0/1 GigabitEthernet0/1 is up, line protocol is up Hardware is CN Gigabit Ethernet, address is fc99.4775.c3e1 (bia fc99.4775.c3e1) Description: Link to LAN 2 Internet address is 192.168.11.1/24 MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation ARPA, loopback not set Keepalive set (10 sec) Full Duplex, 100Mbps, media type is RJ45 output flow-control is unsupported, input flow-control is unsupported ARP type: ARPA, ARP Timeout 04:00:00 Last input 00:00:11, output 00:00:02, output hang never Last clearing of "show interface" counters never Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0 Queueing strategy: fifo Output queue: 0/40 (size/max) 5 minute input rate 0 bits/sec, 0 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec 614 packets input, 125730 bytes, 0 no buffer Received 585 broadcasts (0 IP multicasts) 0 runts, 0 giants, 0 throttles 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored 0 watchdog, 306 multicast, 0 pause input 717 packets output, 77198 bytes, 0 underruns 0 output errors, 0 collisions, 1 interface resets 228 unknown protocol drops 0 babbles, 0 late collision, 0 deferred 0 lost carrier, 0 no carrier, 0 pause output 0 output buffer failures, 0 output buffers swapped out R1# 56 Verify the R1 Serial Interface R1# show interfaces serial 0/0/0 Serial0/0/0 is up, line protocol is up Hardware is WIC MBRD Serial Description: Link to R2 Internet address is 209.165.200.225/30 MTU 1500 bytes, BW 1544 Kbit/sec, DLY 20000 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation HDLC, loopback not set Keepalive set (10 sec) Last input 00:00:03, output 00:00:02, output hang never Last clearing of "show interface" counters never Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0 Queueing strategy: fifo Output queue: 0/40 (size/max) 5 minute input rate 0 bits/sec, 0 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec 714 packets input, 52752 bytes, 0 no buffer Received 714 broadcasts (0 IP multicasts) 0 runts, 0 giants, 0 throttles 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 714 packets output, 53070 bytes, 0 underruns 0 output errors, 0 collisions, 3 interface resets 0 unknown protocol drops 0 output buffer failures, 0 output buffers swapped out 1 carrier transitions DCD=up DSR=up DTR=up RTS=up CTS=up R1# 57 Verify the R1 Interface Status 2001:0DB8:ACAD:1::/64 PC1 PC2 :10 :10 2001:0DB8:ACAD:3::/64 G0/0 :1 :1 G0/1 R1 :1 S0/0/0 2001:0DB8:ACAD:2::/64 R1# show ipv6 interface brief GigabitEthernet0/0 [up/up] FE80::FE99:47FF:FE75:C3E0 Link Local Address (created automatically) 2001:DB8:ACAD:1::1 Global Unicast Address (configured) GigabitEthernet0/1 [up/up] FE80::FE99:47FF:FE75:C3E1 Link Local Address (created automatically) 2001:DB8:ACAD:2::1 Global Unicast Address (configured) Serial0/0/0 [up/up] FE80::FE99:47FF:FE75:C3E0 Link Local Address (created automatically) 2001:DB8:ACAD:3::1 Global Unicast Address (configured) Serial0/0/1 [administratively down/down] unassigned R1# 58 Verify the R1 Routing Table 2001:0DB8:ACAD:1::/64 PC1 PC2 :10 :10 2001:0DB8:ACAD:3::/64 G0/0 :1 :1 G0/1 R1 :1 S0/0/0 2001:0DB8:ACAD:2::/64 R1# show ipv6 interface gigabitEthernet 0/0 GigabitEthernet0/0 is up, line protocol is up IPv6 is enabled, link-local address is FE80::32F7:DFF:FEA3:DA0 No Virtual link-local address(es): Global unicast address(es): 2001:DB8:ACAD:1::1, subnet is 2001:DB8:ACAD:1::/64 Joined group address(es): FF02::1 FF02::1:FF00:1 FF02::1:FFA3:DA0 MTU is 1500 bytes ICMP error messages limited to one every 100 milliseconds ICMP redirects are enabled ICMP unreachables are sent ND DAD is enabled, number of DAD attempts: 1 ND reachable time is 30000 milliseconds (using 30000) ND NS retransmit interval is 1000 milliseconds R1# 59 Verify Connectivity 2001:0DB8:ACAD:1::/64 PC1 PC2 :10 2001:0DB8:ACAD:3::/64 G0/0 :1 :1 G0/1 :10 R1 :1 S0/0/0 2001:0DB8:ACAD:2::/64 R1# show ipv6 route IPv6 Routing Table - default - 7 entries Codes: C - Connected, L - Local, S - Static, U - Per-user Static <output omitted> C L C L C L L R1# 2001:DB8:ACAD:1::/64 [0/0] via GigabitEthernet0/0, directly connected 2001:DB8:ACAD:1::1/128 [0/0] via GigabitEthernet0/0, receive 2001:DB8:ACAD:2::/64 [0/0] via GigabitEthernet0/1, directly connected 2001:DB8:ACAD:2::1/128 [0/0] via GigabitEthernet0/1, receive 2001:DB8:ACAD:3::/64 [0/0] via Serial0/0/0, directly connected 2001:DB8:ACAD:3::1/128 [0/0] via Serial0/0/0, receive FF00::/8 [0/0] via Null0, receive 60 Verify the R1 Interface Status 2001:0DB8:ACAD:1::/64 PC1 PC2 :10 :10 2001:0DB8:ACAD:3::/64 G0/0 :1 :1 G0/1 R1 :1 S0/0/0 2001:0DB8:ACAD:2::/64 R1# ping 2001:db8:acad:1::10 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 2001:DB8:ACAD:1::10, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5) R1# 61 Tweaking Show Command Output R1#show ip interface brief Interface Embedded-Service-Engine0/0 GigabitEthernet0/0 GigabitEthernet0/1 Serial0/0/0 Serial0/0/1 R1# R1#show ip interface brief GigabitEthernet0/0 GigabitEthernet0/1 Serial0/0/0 R1# IP-Address unassigned 192.168.10.1 192.168.11.1 209.165.200.225 unassigned OK? YES YES YES YES YES Method unset manual manual manual unset Status Protocol administratively down down up up up up up up administratively down down | include up 192.168.10.1 YES manual up 192.168.11.1 YES manual up 209.165.200.225 YES manual up up up up 63 Tweaking Show Command Output R1#show ip route | begin Gateway Gateway of last resort is not set C L C L C L R1# 192.168.10.0/24 is variably subnetted, 2 subnets, 2 masks 192.168.10.0/24 is directly connected, GigabitEthernet0/0 192.168.10.1/32 is directly connected, GigabitEthernet0/0 192.168.11.0/24 is variably subnetted, 2 subnets, 2 masks 192.168.11.0/24 is directly connected, GigabitEthernet0/1 192.168.11.1/32 is directly connected, GigabitEthernet0/1 209.165.200.0/24 is variably subnetted, 2 subnets, 2 masks 209.165.200.224/30 is directly connected, Serial0/0/0 209.165.200.225/32 is directly connected, Serial0/0/0 64 Tweaking Show Command Output R1#show running-config | section line con line con 0 password 7 110A1016141D login R1# R1#show ip interface brief | include down Embedded-Service-Engine0/0 unassigned YES unset Serial0/0/1 unassigned YES unset R1# R1#show ip interface brief | exclude up Interface IP-Address OK? Method Protocol Embedded-Service-Engine0/0 unassigned YES unset Serial0/0/1 unassigned YES unset R1# R1#show running-config | begin line line con 0 password 7 110A1016141D login line aux 0 line 2 no activation-character no exec transport preferred none transport input all transport output pad telnet rlogin lapb-ta mop udptn stopbits 1 line vty 0 4 password 7 030752180500 login transport input all ! administratively down down administratively down down Status administratively down down administratively down down v120 ssh 65 Command History Feature R1#terminal history size 200 R1# R1#show history show ip interface brief show interface g0/0 show ip interface g0/1 show ip route show ip route 209.165.200.224 show running-config interface s0/0/0 terminal history size 200 show history R1# The command history feature temporarily stores a list of executed commands: To recall commands press Ctrl+P or the UP Arrow. To return to more recent commands press Ctrl+N or the Down Arrow. By default, command history is enabled and the system captures the last 10 commands in the buffer. Use the show history privileged EXEC command to display the buffer contents. Use the terminal history size user EXEC command to increase or decrease size 66 of the buffer. Routers Operate at Layers 1, 2, and 3 (Decisions made at Layer 3) 67 Remember: Encapsulation These addresses do not change! Layer 3 IP Packet These change from host to router, router to router, and router to host. Destination IP Address Source IP Address Other IP fields Data Layer 2 Data Link Frame Destination Address Next hop Data Link Address of Host or Router’s interface Source Address Type Data Trailer Current Data Link Address of Host or Router’s exit interface Now, let’s do an example… 68 Layer 2 Data Link Frame Dest. Dest.Add MAC MAC 0B-31 FF-FF 00-10 Source Add MAC 0A-10 00-20 Layer 3 IP Packet Type 800 Dest. IP 192.168.4.10 Source IP 192.168.1.10 IP fields Data Trailer This is just a summary. The details will be shown next! Now for the details… 69 Layer 2 Data Link Frame Dest. MAC 00-10 Source MAC 0A-10 Layer 3 IP Packet Type 800 Dest. IP 192.168.4.10 Source IP 192.168.1.10 IP fields Data Trailer 70 Layer 2 Data Link Frame Dest. MAC 0B-31 00-10 Source Source MAC MAC 00-20 0A-10 Layer 3 IP Packet Type Type 800 800 RTA ARP Cache IP Address MAC Address 192.168.2.2 0B-31 Dest. IP 192.168.4.10 Source IP 192.168.1.10 Network 192.168.1.0/24 192.168.2.0/24 192.168.3.0/24 192.168.4.0/24 IP fields Data Trailer Trailer RTA Routing Table Hops Next-hop-ip Exit-interface 0 Dir.Conn. e0 0 Dir.Conn e1 1 192.168.2.2 e1 2 192.168.2.2 e1 71 Layer 2 Data Link Frame Dest. Add MAC FF-FF 0B-31 Source Add MAC 00-20 Layer 3 IP Packet Type 800 Dest. IP 192.168.4.10 Source IP 192.168.1.10 Network 192.168.1.0/24 192.168.2.0/24 192.168.3.0/24 192.168.4.0/24 IP fields Data Trailer RTB Routing Table Hops Next-hop-ip Exit-interface 1 192.168.2.1 e0 0 Dir.Conn e0 0 Dir.Conn s0 1 192.168.3.2 s0 72 Layer 2 Data Link Frame Dest. Dest.Add MAC FF-FF 0B-20 Source SourceAdd MAC 0C-22 Layer 3 IP Packet Type Type 800 800 RTC ARP Cache IP Address MAC Address 192.168.4.10 0B-20 Dest. IP 192.168.4.10 Source IP 192.168.1.10 IP fields Data Trailer RTC Routing Table Network Hops Next-hop-ip Exit-interface 192.168.1.0/24 2 192.168.3.1 s0 192.168.2.0/24 1 192.168.3.1 s0 192.168.3.0/24 0 Dir.Conn s0 192.168.4.0/24 0 Dir.Conn e0 73 Layer 2 Data Link Frame Dest. MAC 0B-20 Source MAC 0C-22 Layer 3 IP Packet Type 800 Dest. IP 192.168.4.10 Source IP 192.168.1.10 IP fields Data Trailer 74 Layer 2 Data Link Frame Dest. Dest.Add MAC MAC 0B-31 FF-FF 00-10 Source Add MAC 0A-10 00-20 Layer 3 IP Packet Type 800 Dest. IP 192.168.4.10 Source IP 192.168.1.10 IP fields Data Trailer The summary once again! 75 Routing Decisions 76 Alex Zinin’s Routing Table Principles I know about my remote networks but it is not my responsibility if R2 and R3 know about their remote networks. Principle 1: Every router makes its decision alone, based on the information it has in its own routing table. R1 makes forwarding decisions based solely on the information in the routing table. R1 does not consult the routing tables in any other routers. Making each router aware of remote networks is the responsibility of the network administrator. 77 Alex Zinin’s Routing Table Principles Just because I know how to get to R3’s LAN, 192.168.2.0/24 and I send that packet to R2, doesn’t mean R2 knows how to get there. ??? Principle 2: The fact that one router has certain information in its routing table does not mean that other routers have the same information. 78 Alex Zinin’s Routing Table Principles And if the packet for R3’s LAN reaches 192.168.2.0/24, I don’t know if R3 has a route back to 172.16.3.0/24 for any return traffic. ??? Principle 3: Routing information about a path from one network to another does not provide routing information about the reverse, or return, path. 79 Best Path Which path is my “best path”? RIP’s metric is hop count OSPF’s metric is bandwidth ? EIGRP is bandwidth + delay Router’s determine best-path to a network: Depends on the routing protocol A protocol used to between routers to determine “best path” Routing protocols use their own rules and metrics. A metric: Quantitative value used to measure the distance to a given route. Best path: Path with the lowest metric. 80 To reach the 192.168.1.0/24 network it is 2 hops via R2 and 2 hops via R4. Equal Cost Load Balancing ? ? 192.168.1.0/24 What happens if a routing table has two or more paths with the same metric to the same destination network? (equal-cost metric) Router will perform equal-cost load balancing. All routing protocols (RIP, EIGRP, OSPF) support equal cost load balancing; EIGRP also supports unequal cost load balancing. 81 Path Determination of the route Administrative Distance If multiple paths to a destination are configured on a router, the path installed in the routing table is the one with the lowest Administrative Distance (AD): • A static route with an AD of 1 is more reliable than an EIGRPdiscovered route with an AD of 90. • A directly connected route with an AD of 0 is more reliable than a static route with an AD of 1. 82 The Routing Table The Routing Table A routing table is a file stored in RAM that contains information about: Directly connected routes Remote routes Network or next hop associations 83 The show ip route and show ipv6 route commands are used to display the contents of the routing table: Local route interfaces - Added to the routing table when an interface is configured. (displayed in IOS 15 or newer) Directly connected interfaces - Added to the routing table when an interface is configured and active. Static routes - Added when a route is manually configured and the exit interface is active. Dynamic routing protocol - Added when EIGRP or OSPF are implemented and networks are identified. 84 Interpreting the entries in the routing table. 85 Directly Connected Interfaces A newly deployed router, without any configured interfaces, has an empty routing table. An active, configured, directly connected interface creates two routing table entries: Local (L) Directly Connected (C) 86 Directly Connected Example A routing table with the directly connected interfaces of R1 configured and activated. 87 Directly Connected IPv6 Example The show ipv6 route command shows the ipv6 networks and routes installed in the routing table. 88 Statically Learned Routes Static Routes Static routes and default static routes can be implemented after directly connected interfaces are added to the routing table: Static routes are manually configured Covered in Chapter 6 89 Static Routes Example 90 Default Static Routes Example 91 Dynamic Routing (Chapters 7 and later) Dynamic routing is used by routers to share information about the reachability and status of remote networks. It performs network discovery and maintains routing tables. 92 IPv4 and IPv6 Routing Protocols Cisco ISR routers can support a variety of dynamic IPv4 routing protocols including: EIGRP – Enhanced Interior Gateway Routing Protocol OSPF – Open Shortest Path First IS-IS – Intermediate System-to-Intermediate System RIP – Routing Information Protocol Cisco ISR routers can support a variety of dynamic IPv6 routing protocols including: RIPng - RIP next generation OSPFv3 EIGRP for IPv6 MP-BGP4 - Multicast Protocol-Border Gateway Protocol 93