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- Below shows the routing table of RT2, with RIPv1 as the routing protocol. RT2 has 2 routes to 10.0.0.0/8 network due to autosummarization. RT2 will perform load balancing across the paths since they are equal-cost paths to the same destination, which will definitely cause malfunctioning on applications! RT2#sh ip route Gateway of last resort is not set 172.16.0.0/24 is subnetted, 3 subnets C 172.16.1.0 is directly connected, Serial0 C 172.16.2.0 is directly connected, Ethernet0 C 172.16.3.0 is directly connected, Serial1 R 10.0.0.0/8 [120/1] via 172.16.1.1, 00:00:20, Serial0 [120/1] via 172.16.3.2, 00:00:15, Serial1 RT2# - This problem can be solved by migrating to a classless routing protocol with autosummarization disabled, eg: RIPv2, EIGRP. Remember to disable autosummarization as it is enabled by default. - As mentioned before, routing protocols are considered either classful or classless. Nevertheless, IP routing can also be considered either classful or classless as well. - The concepts of classful and classless routing are independent of any routing protocol, as the concepts still applicable to IP routing even if only static routes are being used. Note: Classlessness can be a characteristic of a routing protocol or a router. - Classful or classless routing affects how a router uses its default route. A very good topic for the discussion of classful and classless routing is default routing, where packets destined to networks with no specific routes in the routing table will be directed to the default route. - The [no] ip classless global configuration command enables and disables classless routing respectively. Disabling classless routing is equivalent to enabling classful routing. - Note: The classless IP behavior is enabled by default in Cisco IOS Release 12.0 and later. Note: The classless IP behavior has no effect on some later Cisco IOS 12.3 releases. RT1 ISP 150.15.1.0/24 .2 Figure 16-3: Sample Default Routing Network RT1#conf t Enter configuration commands, one per line. End with CNTL/Z. RT1(config)#no ip classless RT1(config)#ip route 0.0.0.0 0.0.0.0 150.15.1.1 RT1(config)#^Z RT1# 119 .1 150.15.100.0/24 10.1.1.0/24 Copyright © 2008 Yap Chin Hoong yapchinhoong@hotmail.com
RT1#sh ip route Gateway of last resort is 150.15.1.1 to network 0.0.0.0 150.15.0.0/24 is subnetted, 1 subnets C 150.15.1.0 is directly connected, Serial0/0 S* 0.0.0.0/0 [1/0] via 150.15.1.1 RT1# RT1#ping 10.1.1.1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 10.1.1.1, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 36/36/40 ms RT1#ping 150.15.100.1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 150.15.100.1, timeout is 2 seconds: ..... Success rate is 0 percent (0/5) RT1#conf t Enter configuration commands, one per line. End with CNTL/Z. RT1(config)#ip classless RT1(config)#^Z RT1#ping 150.15.100.1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 150.15.100.1, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 36/38/40 ms RT1# - As seen from the output above, ping to 150.15.100.1 with classful routing failed, but ping has succeeded with classless routing. This shows even if there is a default route in the routing table, it might not be used! - Cisco IOS uses either classful or classless routing logic when matching a destination IP address with the routes in the routing table and decide when to use the default route. - The classful logic – no ip classless: i) RT1 needs to send a packet to 150.15.100.1. ii) RT1 matches Class B network – 150.15.0.0, a directly connected network. Due to it is running classful routing, the default route cannot be used! iii) RT1 does not have a more specific route to 150.15.100.0 from its routing table. iv) RT1 discards the packet as the default route cannot be used. - The classless logic – ip classless: i) RT1 needs to sends a packet to 150.15.100.1. ii) RT1 does not have a more specific route to 150.15.100.0. iii) The default route is being used as there is no specific route matched. - With classful routing, the default route is only being used when a packet’s destination Class A, B, or C major network number is not in the routing table. Ex: A packet destined to 10.2.1.1 is discarded by a classful router with a routing table that consisting routes to 10.0.0.0/8, 10.1.1.0/24, 10.1.2.0/24, as the major network of 10.2.1.1 – 10.0.0.0, is in the routing table. 120 Copyright © 2008 Yap Chin Hoong yapchinhoong@hotmail.com
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CCNA Complete Guide 2nd Edition Yap
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CCNA Complete Guide 2nd Edition Cop
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Upper Layers Lower Layers Applicati
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Cisco Hierarchical Model - Defined
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Header Length (4) Source Port (16)
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- Socket is a communication channel
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- The length of an IP address is 32
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- The following section discusses s
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- Below lists the 2 sublayers in th
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- Each switch port does not share t
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- Below lists the switch internal p
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Physical Layer - The physical layer
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- Another way to reduce emissions i
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Figure 3-7: Single-Mode and Multimo
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Wireless AP Switch Figure 3-8: 802.
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- Below lists the common IOS CLI er
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RT1#show running-config interface F
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- Cisco IOS treats a mistyped comma
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- Below describes the STP convergen
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- Refer back to Figure 5-1B, assume
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- A switch running RSTP only need 6
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Port Security Configuration - Port
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SW2# 00:25:00: STP: VLAN0001 new ro
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- Both protocols utilize a 12-bit V
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Layer 4 Switching (Content Switchin
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- VTP Pruning provides a way to pre
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VLAN Trunking Protocol Configuratio
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- VLAN information will not be prop
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- Private IP addresses are non-rout
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- Some materials calculate the numb
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Page 71 and 72: Cisco Discovery Protocol (CDP) c250
Page 73 and 74: - CDP is enabled by default. The no
Page 75 and 76: Troubleshooting IP - Internet Contr
Page 77 and 78: - Firstly, PC1 purposely sends out
Page 79 and 80: - Below describes the operation of
Page 81 and 82: Maximum Hop Count Hop count metric
Page 83 and 84: - Invalid Timer specifies how long
Page 85 and 86: - Initial configuration on RT2: Rou
Page 87 and 88: - Static Routing configuration on R
Page 89 and 90: - RIPv1 and IGRP are classful routi
Page 91 and 92: - IGRP configuration on RT2: RT2(co
Page 93 and 94: MISC IP Routing Commands - The pass
Page 95 and 96: - OSPF uses a reliable protocol to
Page 97 and 98: - OSPF areas break up a network so
Page 99 and 100: - EIGRP uses the same formula as us
Page 101 and 102: - Autosummarization EIGRP supports
Page 103 and 104: - OSPF Single-Area configuration on
Page 105 and 106: - The show ip ospf database EXEC co
Page 107 and 108: OSPF Multiarea Configuration Area 1
Page 109 and 110: - Below lists the different termino
Page 111 and 112: - Verify the EIGRP configuration on
Page 113 and 114: - When a link to a neighbor fails,
Page 115 and 116: - Below shows the beauty of VLSM. B
Page 117 and 118: - RT1 and RT3 are summarizing route
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Page 121: - RIPv1 and IGRP perform autosummar
Page 125 and 126: MTU and Fragmentation - Maximum Tra
Page 127 and 128: - Figure 17-1 shows the usage of CI
Page 129 and 130: - Static NAT performs one-to-one ma
Page 131 and 132: 172.16.1.1 172.16.1.2 172.16.1.3 17
Page 135 and 136: - Below shows the IP NAT debugging
Page 137 and 138: - The access list indicates whether
Page 139 and 140: - Access Control List (ACL) is the
Page 141 and 142: - Below lists some other usages of
Page 143 and 144: - Standard IP Access Lists configur
Page 145 and 146: RT2#sh access-lists example01 Exten
Page 147 and 148: WAN Network RT1 CSU/DSU CSU/DSU RT2
Page 149 and 150: Remote Access Technologies - Remote
Page 151 and 152: Digital Subscriber Lines (DSL) - DS
Page 153 and 154: Point-to-Point Serial Links (Leased
Page 155 and 156: - Comparisons between synchronous a
Page 157 and 158: - PPP Encapsulation configuration o
Page 159 and 160: - The function of the username {rem
Page 161 and 162: - 3 LMI protocol options are availa
Page 163 and 164: - Comparisons between Frame Relay L
Page 165 and 166: RT1 RT2 RT3 Figure 23-7A: RT1 with
Page 169 and 170: - IETF Frame Relay encapsulation ty
Page 171 and 172: RT1 Frame Relay RT2 DLCI 101 Frame
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- The interface serialx.y point-to-
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- Frame Relay Multipoint Subinterfa
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- Rate Shifting or Adaptive Rate Se
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- By operating in the 5GHz radio ba
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- Every packet from every access po
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Virtual Interface (mandatory) Servi
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Wireless Security - Organizations t
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Wireless Management - WLANs require
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Cisco Wireless LAN Configuration -
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- ISDN offers very fast call setup
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- ISDN was designed to reuse the ex
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- ISDN PRIs are often being used fo
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- Routing protocols are unable to l
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DDR Step 4: Determining when to ter
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- The show interfaces bri{num:0 | 1
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DDR Dialer Profiles Configuration -
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- Note: IP addresses are configured
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- Below show the routing tables on
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- The configuration above defines 2
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cisco Systems, Inc. 170 West Tasman
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Catalyst Switch IOS Upgrade Procedu
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Catalyst Switch IOS Upgrade Procedu
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Cisco Router Password Recovery Proc
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Catalyst Switch Password Recovery P
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Switch> Switch>en Switch#rename con
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- The 3 possible Frame Relay PVC st
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Constructing a Compound Frame Relay
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8. Once the frame is completed, it
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Decimal Hex Binary Decimal Hex Bina
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MISC Basic Networking Notes - The m
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MISC Data Link Layer Notes - Ethern
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- The 5-4-3 repeater deployment rul
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Ethernet Autonegotiation and Duplex
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The TCP Connection States timeout s
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- Q: How does a client application
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- Urgent Data Pointer (16 bits) ind
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TCP Selective Acknowledgment (SACK)
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- Local Proxy ARP is used when ther
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Spanning Tree Protocol Port ID - Wh
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The Problem of Router-on-a-Stick Co
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- Sample Subnet Zero configuration:
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The permanent keyword in the Static
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RIPv1 and VLSM RT1 RT4 Figure A6-9:
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- Below shows the NAT operations on
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Bidirectional (2-Way) NAT PC1 172.1
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- Note: A router does not require a
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The Access Control List established
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Switch Port Access Control Lists -
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- Below shows a sample Dynamic Acce
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Router(config)#ip access-list exten
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Optional PPP Commands - The compres
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- Below shows the output of the PPP
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- Below shows the output of the PPP
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- Below configure the username and
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IEEE 802.11 Standards and Specifica
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- Figure A6-20 shows the frame form
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- Below lists the IEEE 802.11 manag
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IEEE 802.11 Types and Subtypes Type
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Client (Supplicant) EAPOL-Start EAP
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- IPsec-based VPN is comprised of 2
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- IPsec supports the following 3 ty
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Version Header Length Time To Live
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- The authentication pre-share ISAK
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Troubleshooting ISDN E1/T1 Physical
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- Below addresses ISDN E1/T1 contro
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Troubleshooting ISDN Layer 2 - Unde
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Troubleshooting ISDN Layer 3 - Only
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ISDN Loopback Test Call - In a loop
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96 Number changed. The called numbe
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C2 Channel type not implemented. Th
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locking state, STP, 39 BNC, 27 bool
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show vlan, 57 show vtp status, 58 s
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framing, 22 MAC addresses, 22 stand
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K keepalives EIGRP, 95 Frame Relay,
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PAT (Port Address Translation), 127
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star topologies, 25 startup-config
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