Cisco CCNA

cisco CCNAThe following notes were made while revising for my Cisco CCNA exam. They are not in any way a complete set of revision notes, but more like a last minute refresher for those bits of information that are important and need to be remembered.

If you find this page useful check out my other revision pages:
 Last minute revision guide
 Cisco IOS commands
 Layer 2 switching
 Spanning Tree Protocol - STP
 Novell IPX
 Access Control Lists - ACL
For other useful CCNA study guides, CCNA practice exams and technical training, see my certification and networking links page.

Cisco CCNA Certification Study Guide

 Ctrl+Shift+6 then X - Allows you to open more than one telnet session.
 Only the Hardware addresses change when packets go through routers.
 Half duplex Ethernet - One station can only send or receive at any time.
 Ethernet Frame - 64bytes Min 1518bytes Maximum.
 ISL frames are 1522bytes long, this can be mistaken for Giants and lost. Have to use ISL NIC cards. On router interface use 'encapsulation isl 2' to use ISL frames on VLAN 2.
 FX and SX are fibre media, 100VG-AnyLAN is twisted pair copper media.
 Spanning Tree is IEEE 802.1d - created by DEC (Digital Equipment Corp).
 BPDUs are Multicast frames, sent every 2 seconds. Blocked ports still receive BDPUs.
 Forward delay - Time taken from listening to learning (approx 50 seconds)
 Default IEEE bridge priority 32,768, used to select root bridge. If these are identical then switch with lowest MAC address is used.
 ISDN Protocols - E = Telephone network standards, I = Concepts, Terminology, Q = Switching, Signalling methods.
 ISDN Reference Points - R = non-ISDN device and TA, S/T = references point between NT1 and NT2, U = NT1 and ISDN network (US only)
 TE1 = Device compatible with ISDN, TE2 = Device NOT compatible with ISDN, TA = Converts non ISDN signals to ISDN signals, NT1 = Converts 4 wires into 2 wire local loop, NT2 = Providers equipment (Switch, PBX)
 BRI - 2 * B-channel 64kbps, 1 * D-channel 16kbps (D-channel - LAPD)
 PRI (Europe, Aus) - 30 * B-channel 64kbps, 1 * D-channel 64kbps (20.48Mbps)
 PRI (EUS, Japan) - 23 * B-channel 64kbps, 1 * D-channel 64kbps (1.544Mbps)
 ISDN supports IP, IPX, Appletalk...
 ISDN can use PPP, HDLC, LAPD, each B-channel needs a SPID
 Use static routes for ISDN otherwise it will keep link open.
 MAC address 48 bits (12 Hex), IPX address 80 bits.
 Netware 3.11 (1983-) - ethernet_802.3/novell-ether (Cisco default on Ethernet networks), Netware 3.12 or later (1985-) - Ethernet_802.2/sap - includes LLC, Ethernet_II - arpa, Ethernet_SNAP - snap, Netware 4.11 - use sap, Netware 5 uses IP
 Novell RIP - Metrics = ticks and hops (15 max), 60 sec updates (tick = 55ms / 1/18 sec)
 Novell 4.11 > uses NLSP (Netware Link Service Protocol) Link State Routing
 SAP - Updates 60 Secs - 4 = Netware file server, 7 = Print server, 24 = Remote bridge server
 Ping Responses - U = unreachable, C = congestion, I = user interrupt,? = unknown packet type, & = lifetime exceeded
 Trace Responses - N = Network unreachable, !H = Not forwarded due to ACL restriction, P = Protocol unreachable, U = Port could not be reached
 Ethernet 5-4-3 rule = Between 2 nodes there can only be max 5 segments, 4 repeaters and only 3 segments must have users.
 80/20 rule - 80% of traffic should be local 20% across backbone
 Class 1 repeater (translational) - delay 140 secs, number you can use 1
 Class 2 repeater (transparent) - delay 92 secs, number you can use 2
 CSMA/CD - Used on half duplex devices
 Auto-negotiate on FastEthernet checks link speed and duplex of line.
 Protocol field in IP header - TCP = 6, UDP = 17, ICMP = 1, IGRP = 9
 Ports - 20 FTP data, 21 FTP program, 23 - telnet, 25 - SMTP, 69 - TFTP, 53 - DNS, 80 - HTTP
 Loopback address -
 ACL - Standard ACL as close to destination as possible, Extended ACL as close to source as possible
 IP = 1-99, Ex IP = 100-199, AppleTalk = 600-699, IPX = 800-899, Ex IPX = 900-999, IPX SAP = 1000-1099
 Remember that there is an explicit ACL of 'deny all' if no statements match.
 Multiprotocol routing supports more than one routing protocol, allows a router to deliver packets from several routed protocols.
 Core Layer - High speed switching - free from filtering or anything which will slow packets etc.
 Distribution Layer - Packet manipulation, address area segregation, broadcast domains, VLANs, security (ROUTERS), WAN access, queuing, firewalls, multicast domains, ACLs
 Access Layer - End users, ACL/filters, remote access, shared bandwidth (SWITCHES), segmentation, DDR
 HSSI - 52Mbps max
 ATM cell size - 53bytes
 Cisco LMI - DLCI - 16-1007, ANSI LMI - DLCI 16-992 (DLCI = 10bits)
 LMI is a special DLCI = 1023
 LMI Multicasting reserved for 1019-1022
 LMI extensions - Virtual circuit status, multicasting, global addressing, simple flow control
 LMI types Cisco (default), ansi, q933a. From IOS 11.2 LMI is auto-sensed
 Class A - 1-126
 Class B - 128.1-191.255
 Class C 192.0.1-
 Class D - (1110 highest order bits) - remaining bits for multicasting
 Class E - (1111 highest order bits) - Reserved for future use
 RIP 1 (Classful), single subnet, periodic updates of full routing table, max hop count 15
 RIP 2 (Classless addressing), triggered updates, full routing table updates
 Directed Broadcast - All host bits set to 1 received by all hosts on local broadcast domain.
 Local Broadcast ( - All bits set to 1 received by all hosts on local and remote broadcast domains.
 Synchronous serial links default to HDLC on Cisco routers
 VIP cards - type slot/port adapter/interface (e.g e/1/0/2) (remember first interface is 0 not 1)
 IGRP Metrics - Delay, Bandwidth
 Default route - ip route - need to use 'ip classless' (Classless is enabled by default on IOS 12.x) (Only work on stub networks)
 ip default-network
 CDP timer default 90 secs, holdtime 240 secs
 Trunked links - FastEthernet or GigabitEthernet only
 Frame Tagging - ISL = Adds it's own FCS, Cisco propriety (default), IEEE 802.1q
 LAN Emulation (LANE) - Used for multiple VLANS over ATM
 802.10 - FDDI Frame Tagging
 Hosts can only communicate between VLANS using Layer 3 devices
 VTP Modes - Server (Default for Catalyst switches) Need at least one server in a VTP domain. All changes are advertised. Client - Sends and receives updates. To make a switch a server make it a client first then promote it once it's VTP database has received the latest revision. Transparent - Does not participate in VTP domain, but forwards VTP ads through trunked links. They keep their own database.
 VTP adverts sent every 5 mins or when a change occurs, changes only kept by other switches if higher rev no than their current version.
 VTP pruning - If a switch does not have any ports configured for VLAN 5 then it won't receive updates for it. Disabled by default. Enabled across entire domain if configured. VLAN 1 is not pruning eligible.
 Config Reg - 00 Rom Monitor, 01 Boot Image from ROM, 02-F NVRAM, Bit 6 set to 1 to ignore NVRAM. Register is 16 Bits.
 1900 Switch Config - enable password level 1 - usermode, level 15 - enable password.
 1900 switch can have up to 64 VLANS. You cannot telnet from a switch but you can telnet into it.

Administrative Distances
Routing Protocol Administrative Distance
Connected Intf 0
OSPF 110
Static route 1
RIP 120
IGRP 100

• RIP - Updates 30 secs, Max Hops 15, Invalid 90 secs, Flush 240 secs, metrics hops, load balance 6 equal cost links
• IGRP - Updates 90 secs, max hops 255 (default 100), invalid 3x90 secs, holddown 3x90+10 secs, flush 7x90 secs, metrics bandwidth, delay, load balance upto 6 unequal cost links.
• When routers are converging no data is sent.
• Frame Relay - 64 kbps - 1.544 Mbps, non-broadcast multi-access encapsulation (NBMA), dynamic bandwidth allocation, congestion control. Can use PVC and SVCs, PVC more common. Virtual circuit established before data sent. Encapsulation Cisco (Default), IETF (use when connecting non-cisco routers). Static routes are more stable than IARP.
• Routers are DTE devices by default, DCE interfaces need a clock rate.
• Telneting uses layers 1-4 so a good test of functionality. If you type a command the router doesn't know or type and IP address it will try to resolve the name and telnet.
• Bandwidth command sets cost for serial links. This is only used by routing protocols so they can 'cost' paths. Default = 1.544kbps (T1) Command is in Kbps.
• Clock rate command is in bps.
• HDLC - Connection-orientated, operates at the datalink layer, small overhead, no way of distinguishing network protocols. Every vendors implementation is different, NO authentication, CISCO Default over serial lines.
• LAPB - Connection-orientated, datalink layer protocol, HUGE overhead, uses windowing, used instead of HDLC for error prone links.
• PPP - industry standard, used when connection between different vendors devices. NCP to identify network protocol, authentication, compatible with async + sync links, operates at physical + datalink layers only. PAP - insecure authentication, CHAP auth provides initial + periodic auth. PPP compression uses stacker and predictor methods. Error detection - PPP uses quality and magic number methods. Multilink - IOS 11.1 only, spreads the load over 2 parallel circuits (bundle).
• Ethernet 0 is up, line protocol is down - keepalive or framing issue, check keepalives on both sides should match, check clocking on DCE, check encapsulation on both ends.
• Ethernet 0 is down, protocol is down, - carrier detect is not present, other end maybe administratively shutdown or interface or cable problem.
• Ethernet 0 is administratively shutdown - the 'no shutdown' command has not been issued on the interface.
• Show interface serial 0 - shows bandwidth, MTU, keepalives.
• MTU default = 1500bytes.
• Bandwidth default = 1.544Kbps (T1)
• Keepalives default = 10 seconds.
• Use a cross over cable to connect devices of the same type (e.g router Ethernet intf to router Ethernet intf)
• Cross over cables swap pins 1 and 3 RD, and pins 2 and 6 TX
• STP - 10-100Mbps - 100metres
• ScTP - 10-100Mbps - 100metres
• UTP - 10-100Mbps - 100metres
• Coax - Coaxial - 500metres
• Fiber - Single Mode upto 3000metres
• Fiber - Multimode upto 2000metres
• Connectionless protocols rely on application layer protocols for error handling and delivery.
• EIGRP holds separate routing tables for IP,IPX,Appletalk, but only uses one protocol to distribute the updates.
• CDP uses SNAP (Subnetwork Access Protocol) to enable neighbouring devices to exchange data.
• IPX NLSP - link-state routing protocol intended to replace IPX RIP and SAP
• NCP - Netware Core Protocol - Provides clients with access to server resources
• IPX SAP - Sent every 60 seconds - includes all known services.
• sap is Cisco default for Token Ring networks, SNAP is default for FDDI networks
• VTP allows VLANs to be trunked over Ethernet, ATM, LANE or FDDI
• Gigabit Ethernet using Multimode Fibre can run up to 260m
• 100BaseFX up to 400m
• VLAN Management Policy Server - Must be configured with all hosts' MAC addresses for dynamic allocation.
• Standard ping - 5*100 byte ICMP echos, time out 2 seconds
• DHCP uses UDP packets
• Passive interface command stops interface sending routing updates, but still receives them.
• 2 ways to configure VLAN membership, statically or dynamically through VLAN Management Policy Server.
• ISL and Trunk protocol used to configure trunking on a switch.
• Pre 10.3 IOS commands Config Net - copy config from tftp to DRAM Config Mem - copy NVRAM to DRAM
• IP routing table [administrative distance/composite metric]
• IPX routing table [ticks/hops]


Show version - software version, config files, boot images, config register, basic config of router
Show ipx interface - status, ipx rip and sap received/sent, ipx access-lists
Show ipx route - ipx routing table
Show ipx servers - server list (name, port, hops, type of service)
Show ipx traffic - number/type of packets, RIP and SAP packets
Show protocol - ipx addresses of an interface, IP addresses and routing protocol
Show ip protocol - routing update times, networks active on, neighbour routers, administrative distances, AS number
Show access-lists - shows standard and extended access-lists on all interfaces
Show access-list 101
Show ip interface - IP addresses, masks, MTU, access-lists, split horizon, ICMP, CDP status, NAT statistics, LMI info, DLCIs
Show interface serial 0 - shows bandwidth, MTU, keepalives
Show ip route - ip routing table
Show cdp neighbor - deviceID, local intf, holdtime, capability, platform, remote portID
Show cdp entry * - IP address of neighbour, protocol info, platform, capability, portID, holdtime, same info as show version, neighbour device ID, local interface
Show cdp neighbor detail - same as above also IP address, version info
Show cdp traffic - info on traffic and errors
Show cdp interface - encapsulation, timer, holdtime for each intf
Show controllers serial 0 - shows DTE/DCE connections, buffer size, collisions, mac address
Show host(s) - shows hostname to IP resolution of hosts
Show session(s) - shows connections to a remote device
Show users - shows connections to your router, port and time connected
Show frame-relay lmi - lmi errors and lmi type
Show frame-relay pvc - all configured PVC's, DLCI numbers, status of connections, No. of BECN/FECN
Show frame-relay pvc 16
Show frame-relay map - ip to dlci mappings
Show run - display router config (RAM), configured PVCs, ACLs.

Show mac-address-table
Show run
Show ip - like ipconfig
Show port system - shows switching method
Show vtp
Show trunk A allowed-vlans - shows which VLANS allowed on trunk link
Show vlan-membership
Show vlan 2
Show vlan - verify VLAN config
Show history - shows last 10 commands entered by default
Show terminal - shows terminal config + history buffer size

Banner exec - for activation or incoming vty
Banner incoming - displayed on reverse telnet sessions
Banner login - displayed on all connected terminals. Displayed before MOTD banner but before login prompts
Bfe - manual emergency mode setting
Clear counters - clears counters on all interfaces
Clear frame-relay-inarp - clears dynamic mappings
Clear line 1 - clears vty 1 connection to a remote router
Clock set 10.30.10 28 may 2002
Config-register 0x2102 - changes config register
Copy flash tftp
Copy tftp flash - copies IOS image from tftp server default directory to router flash
Disable - to get back to user mode from privileged
Disconnect 1 - clears a connection to a remote router
Enable - to get into privileged mode
Enable last-resort - define enable action if no tacas servers respond
Enable use-tacas - tells the router to authenticate passwords through a tacas server
Encapsulation isl 3 - encapsulates ISL frame-tagging for VLAN 3 on an interface
Exec timeout 0 1 - sets console timeout to 1 second
Exec-timeout 0 0 - sets exec timeout to never timeout
Exec-timeout 1 0 - set exec timeout to 1 minute
Ip domain-lookup - enables DNS (use no form to stop this)
Ip domain-name - appends domain name to hostname (required for DNS)
Ip host nik - adds to host table (up to 8 ip addr)
Ip name-server - sets ip address(es) of DNS servers
Lock - locks the terminal
Logging synchronous - stops console messages overwriting commands
Logout - to logout of the router
Media-type 100BaseX - sets media type
Mrinfo - request neigbour and version information from a multicast router
No login - sets line, vty ports not to prompt for login info
Passive-inteface s0 - disables routing updates on interface (Global command) - they are not sent out this interface but they are still received.
Ping ipx 40.0000.0c8d.5c9d
Service password-encryption - encrypts passwords (Global command)
Terminal monitor - needed to view debug commands from telnet session
Terminal history size 50 - sets command history to 50 lines
Tftp-server system - Make router a tftp server

Interface Ethernet 2/0/1 - type slot / port adapter / port number (interface) for VIP cards
Config terminal - configures RAM
Config network (config net) - changes a config on a tftp host
Config memory - configure NVRAM
Ip address secondary - adds a secondary subnet address to an interface
Clock rate 56000 - sets clock rate to 56kbps for DCE interfaces

Access-enable - creates a temporary access-list entry
Access-template - creates a temporary access-list entry
Access-profile - apply user profile to interface

Access-list 1 permit - same as next line
Access-list 1 permit any - permits any host
Access-list 1 permit - same as next line
Access-list 1 permit host - permits host
No access list 1 - deletes access list 1
Ip access-group 1 out (out is default)
Access-list 101 deny tcp any eq telnet
Access-list 101 permit ip any any established (TCP connection)
Router(Config)#ip access-list standard nik
Router(Config std-nacl)#deny any log (log - logs packets)

No ip access-group in - won't delete inbound lists if you leave the in off the end of the command

Router(Config)#int s0
Router(Config-if)#encapsulation frame-relay cisco (default)
Router(Config)#int s0.16 point-to-point
Router(Config-if)#no inverse-arp
Router(Config-if)#ip address
Router(Config-if)#bandwidth 64 - sets bandwidth to 64kbps (Only used by routing protocols)
Router(Config-if)#frame-relay map ip 16 ietf broadcast - broadcast tells the router to send broadcasts out this intf

Router(Config)#router igrp 50
Router(Config-router)#timers basic 15 45 0 60
Router(Config-router)#variance 1-128 (controls load balancing between best and worse metrics)
Router(Config-router)#traffic-share balanced/min
Balanced - share inversely proportional to metrics
Min - use routers that have only min costs
Router(Config-router)#no metric holddown
Router(Config-router)#metric maximum-hop 50

Router(Config)#ipx routing - enables IPX routing, RIP and SAP
Router(Config)#ipx maximum-paths 2 - enables equal cost load balancing over 2 paths
Router(Config)#ipx per-host-load-share - ensures all packets to 1 destination are sent over same line
Router(Config)#int e0
Router(Config-if)#ipx network 10 encapsulation sap secondary - assigns ipx network 10 to a secondary interface on Ethernet 0 with encapsulation Ethernet_802.2
Router(Config-if)#ipx delay 6 - sets tick metric for IPX RIP (LAN = 1, WAN = 6 default)

Router(Config)#interface bri 0
Router(Config-if)#ip address
Router(Config-if)#no shutdown
Router(Config-if)#dialer-group 1
Router(Config-if)#dialer map ip name 8042 8350661
(Next router ip - hostname of next route (auth) - number to dial)
Router(Config-if)#dialer load-threshold 2 either - makes both interfaces come up immediately
Router(Config-if)#dialer load-threshold 255 either - only brings up 2nd B-channel if first is 100% loaded
Router(Config-if)#hold-queue 75 in - holds 75 packets in the queue during connection
Router(Config-if)#dialer idle-timeout 300 - sets idle time out (120 default)
Router(Config-if)#encapsulation ppp
Router(Config)#dialer-list 1 list 110
Router(Config)#access-list 110 permit tcp any any eq smtp
Router(Config)#access-list 110 permit tcp any any eq telnet

Ip route = default route
Ip default-network
Ip route serial 1 1 permanent - keeps static route even if router cannot communicate with it, administration distance 1

Cdp timer 90
Cdp holdtime 240
Cdp enable (no cdp enable)

#config t
(Config)#enable password level 1 nikolas - usermode password
(Config)#enable password level 15 makris - enable password
(Config)#enable secret nik2 - precedes the enable p/w
(Config)#hostname nik
(Config)#vtp pruning enable - enables pruning on whole switch
(Config)#delete vtp - deletes VTP database
(Config)#vtp server (client/transparent)
(Config)#vtp domain nikolas
(Config)#vtp password cisco
(Config)#ip address
(Config)#ip default-gateway
(Config)#switching-mode store-and-forward (fragment-free)
(Config)#vlan 2 name sales
(Config)#vlan 3 name marketing
(Config)#int Ethernet 0/1 - slot 0/port 1
(Config-if)#vlan-membership static 2
(Config-if)#description Finance_VLAN
(Config-if)#port secure max-mac-count 1 - allows only one mac address per port
(Config)#int f0/26
(Config-if)#trunk on - enables trunking of all VLANS not just VLAN 1
(Config-if)#no trunk-vlan 3 - stops trunking vlan 3
(Config-if)#duplex full - sets to full duplex (auto sense default)
(Config)#copy tftp:// opcode - download into flash memory
(Config)#copy nvram tftp://
(Config)#copy tftp:// nvram
(Config)#delete nvram - deletes config
(Config)#delete vtp - deletes VTP database
(Config)#clear mac-address-table [dynamic]

Debug ipx routing activity - info on RIP updates
Debug ipx sap - info on sap updates
Debug ip igrp events - what's being rec'd sent, route type (int/ext,system), source, dest
Debug ip igrp transactions - shows contents of routing updates
Debug ip rip - source/contents of updates, network, metrics
Debug frame-relay lmi - enables verification of connection
Debug ppp authentication


Layer 2 Switching
 Switches use Application-Specific-Integrated Circuits (ASIC's) to build and maintain filter tables.
 Switching provides:
 Hardware-based bridging
 Wire speed
 Low latency
 Low cost
 Layer 2 switching breaks up collision domains making a flatter network than an ordinary 10BaseT network.
 Cisco 80/20 rule - Make sure users spend 80% of their time on the local segment.
 Broadcasts, multicasts and slow converging spanning tree limits the size of a switched network.
 Bridges are software based (slower) compared to switches which are hardware based.
 Bridges can only have one Spanning Tree instance per bridge.
 Bridges can only have up to 16 ports.
 Trashing the MAC table - Occurs when there is a loop in a switched network and the MAC filter table is being constantly updated.
 Ethernet is half duplex - Only one station can send or receive at any one time.
 Full duplex Ethernet allows transmission and reception at the same time. Two pairs of wires, full duplex NIC cards and a switched connection are required.
 Switches segment collision domains but forward broadcast packets to all ports.
 Ethernet 5-4-3 rule - Between any 2 nodes there can only be a maximum of 5 segments, 4 repeaters and only 3 of those segments can have hosts.

Switch Memory Buffering - 2 Types (Port Based and Shared Memory)
 Port Based can cause problems holding up transmission of all other packets if there is a delay on one port.
 Shared Memory Buffering is not linked to a specific port but dynamically allocated within a shared pool of memory.

Switching Methods
 Store and Forward - Entire frame is received before forwarding is commenced. Error detection is high, latency low.
 Cut through - Comes in 2 types (Fast Forward and Fragment Free).
1. Fast Forward - Forwards frame after receiving destination address, error prone.
2. Fragment Free - Filters out collision packets (If packet data > 64bytes ok)
 Ethernet frame maximum size = 1518bytes (All of this is received before forwarding by Store and Forward)
 Ethernet frame minimum size = 64 bytes (Only this much of packet read by Fragment Free)

Repeaters - 100BASE-T LANs
Type Max delay Max number you can use
Class 1 repeater (Translational) 140 1
Class 2 repeater (Transparent) 92 2


 Increase security and ease administration and relocation.
 Break up broadcast domains.
 VLANS work at layer 2 and 3 of OSI model.
 Communication between VLANs uses layer 3 routing.
3 ways of assigning a switched port to VLANs:
 Port-Centric - All nodes connected to ports in the same VLAN are assigned to the same VLAN ID.
 Static VLANs - Statically assign ports to a VLAN.
 Dynamic VLANs - Ports that can automatically determine their VLAN assignments based on MAC addresses.
 Switches segment LANs into individual collision domains, VLANs break up broadcast domains as well.

VLANS and Frame Tagging
Access Link - Only part of one VLAN (native VLAN of the port), any devices attached to an access link are unaware of VLAN membership.
Trunk Links - Trunks can carry multiple VLANS. Supported on fast or gigabit links only. Used to transport VLANS between devices.
Frame Tagging and Frame Tagging formats:
 ISL (Inter-Switch Link) is Cisco's Proprietary frame tagging format.
 IEEE 802.1q IEEE standard.
 ISL - 26 bytes long + 4 bit FCS (frame check sequence)
 ISL only used on fast and gigabit Ethernet.
 802.1q - Use IEEE standard if you are trunking between non-Cisco switches. Since IEEE frame tagging actually inserts a field in the frame.
 LANE (LAN Emulation) - Used to communicate multiple VLANS over ATM.
 802.10 (FDDI) - VLAN communication over FDDI, uses SAID field in frame (Cisco Proprietary)
 Frames with ISL frame tagging are over the maximum length specified by the Ethernet standard, these will be recorded as giants if frame tagging is not enabled. Maximum Ethernet frame is 1518 bytes, ISL tagged frames can be up to 1522 bytes long.
 ISL NIC cards are available for servers.
 ISL information is only added to frames that are forwarded out of configured trunk links.
 ISL information is removed if it is forwarded out an access link.
 Trunking makes a single port able to be part of multiple VLANS.
 Non trunked links between switches forward VLAN1 information only.
 Dynamic Trunking Protocol (DTP) - Manages trunk negation.
 Communication between VLANS requires layer 3 devices (Routers)
 Cisco 1600, 1700, 2500 do not support ISL.

VTP - VLAN Trunk Protocol
 VTP manages all configured VLANS across a switched network. VTP provides:
 Tracking and monitoring of VLANS.
 Consistent VLAN configuration across all switches.
 VLANS to be trunked across mixed networks.
 Reporting of new VLANS.
 Plug and Play VLAN configuration.
 VTP is not needed if you only have 1 VLAN.
 VTP advertisements sent every 5 minutes or when a change occurs. Switches only overwrite information with a higher revision number.

VTP Modes of Operation
Server (Default for Catalyst switch) - You need at least one server in a VTP domain. All changes are advertised in VTP domain.
Client - Receives info from VTP servers. Sends and receives updates but cannot make changes. To promote a switch to a server make it a client first, to receive all VTP info, then promote it to a server.
Transparent - Does not participate in a VTP domain, but forwards VTP advertisements through trunked links. Transparent switches keep their own database so you can add or delete VLANS from it (Locally significant).

VTP Pruning
Reduces bandwidth, by reducing broadcasts, multicasts etc that are unnecessary. If a switch does not have any ports configured for VLAN 5 then it will not receive the VTP update.
 VTP Pruning is disabled by default on all switches.
 When VTP Pruning is enabled it is enabled across the entire domain.
 Only VLANs 2-1005 are pruning-eligible.
 VLAN1 is an administrative VLAN.

CISCO CCNA - SPANNING TREE PROTOCOL - 802.1d - Algorithm by Radia Perlman

Spanning Tree Protocol
The Spanning Tree Protocol was created by DEC (Digital Equipment Corporation) now Compaq. This is not compatible with the IEEE 802.1d version which Cisco use.
The Spanning Tree Protocol:
 Prevents loops, loops cause broadcast storms
 Allows redundant links
 Resilient to topology changes
 STA (Spanning Tree Algorithm) - Used to calculate loop-free path
 BPDUs (Bridge Protocol Data Units) are sent and received by switches in the network every 2 seconds (default) to determine spanning tree topology.
Bridge Priority - Numerical value held by switches. All Catalyst switches are 32768
Bridge ID = MAC Address

Spanning Tree States
Blocking No frames forwarded, BPDUs heard
Listening No frames forwarded, listening for frames
Learning No frames forwarded, learning addresses
Forwarding Frames forwarded, learning addresses
Disabled No frames forwarded, no BPDUs heard

STA - Spanning Tree Algorithm
Spanning Tree Algorithm is used to calculate a loop-free path.
All switch ports are in blocking mode to begin with. It takes approx 30 seconds until packets can be forwarded.
Step 1 : Elect Root Bridge - Lowest bridge priority, if there is a tie then switch with lowest bridge ID
Step 2 : Elect Root Ports - Locate redundant paths to root bridge; block all but on root. Root Path Cost is cumulative cost of path to root bridge. Ports directly connected to Root Bridge will be root ports, otherwise lowest root path cost used.
Step 3 : Elect Designated Ports - Single port that sends and receives traffic from a switch to and from Root Bridge - Lowest cost path to Root Bridge.

Spanning Tree Overview
 There can only be one Root Bridge.
 Root-Bridge ports are called 'Designated' and are set to send and receive traffic (forwarding state). All other redundant links to the root bridge are shutdown.
 Blocked ports still receive BPDUs.
 Convergence occurs when switches have transitioned to either forwarding or blocking states. No other data is forwarded during this time.
 Forward delay - Time taken for a switch to go from Listening to Learning (50 seconds default).
 IEEE default priority = 32,768, this is true for all devices running STP IEEE version.
 Port Fast Mode - Immediately brings a port from blocking to forwarding state by eliminating forward delays.
 Bridges can only have one spanning tree instance compared to switches which can have many.
 Bridge Protocol Data Units send confirmation messages using multicast frames.

CISCO CCNA - ISDN - Integrated services Digital Network

ISDN - Integrated services Digital Network
 Carries a variety of traffic. Video, Circuit Switched Data And Telephone Services using normal phone network.
 Call set up and data rates faster than modem.
 Operates at layer 1 to 3.
 ISDN uses SS7 signalling to set up a path with a remote switch.

ISDN Physical layer
 ISDN frames differ depending on inbound (network to terminal NT format) or outbound (terminal to network TE format).
 ISDN frames are 24 bits long.
 ISDN BRI service offers 2 B channels operating at 64kbps which can be used independently from one another for user data or voice traffic.
2*(2*8B + 2D + 6F) sent in pairs
ISDN BRI sent at 8000/sec
(1*8B + 2D + 6F) = 24*8000 = 192kbps
but effective data rate = 2*8B = 16*8000 = 128kbps

ISDN Data link layer
 ISDN datalink layer is LAPD - Link Access Procedure D channel - ensures control and signalling information flows properly.
 D channel operates at 16kbps and is used to carry control and signalling information.
 Terminals cannot transmit into D channel unless they first detect a specific number of ones (indicating no signal). If the TE detects a bit in the echo (E) channel that is different from it's D bits then it stops transmitting immediately.

ISDN SPIDs - Service Profile Identifiers
You also need to know your assigned SPID to identify your configuration at the CO.
 SPIDs allow multiple ISDN devices to share local loop.
 SPIDs are processed during each call set up.
 SPIDs assigned by your service provider.
 A SPID is required for each B channel.

ISDN Devices
TE1 - Device compatible with ISDN network, connects to NT1 or NT2
TE2 - Device not compatible with ISDN requires TA
TA - (terminal Adapter) Converts signals so non-ISDN devices can use ISDN
NT1 - Connects 4-wire ISDN to 2-wire local loop
NT2 - Directs traffic to and from different subscriber devices and NT1

ISDN Reference Points
R - References points between non-ISDN device and TA
S - References points that connect into NT2 (Inbound)
T - References Outbound connections from NT2 into ISDN network or NT1
U - References connection between NT1 and ISDN network (North America only)

ISDN Protocols
E - Telephone network standards
I - Concepts, terminology, general methods
Q - How switching should operate

Dial on Demand Routing - DDR
Before setting up a dial on demand connection you must consider what kind of traffic will initiate the dial up connection, consider the following points:
 You must first establish how ISDN connections will be initiated, established and maintained.
 You must establish which sites are involved, who can initiate and terminate connections.
 Applications supported over DDR, which applications can initiate a connection.
 What unexpected protocols could cause a connection to be made.

ISDN switch types
For proper ISDN configuration you have to configure the correct switch type. Most common type in US is At&T's 5ESS and Nortel DMS-100. In UK it's Net3 and Net5.

Novell Internet Packet Exchange (IPX)

Novell IPX
 IPX is a connectionless layer 3 protocol like IP. An IPX address is made up of 32 bits network and 48 bits MAC address (80 bits in total). It is important you know the length of these in binary and hexadecimal.
 SPX (Sequenced Packet Exchange) is a connection-orientated layer 4 protocol similar to TCP.
 NCP (Netware Core Protocol) - Client server connections and applications communication.
 SAP (Service Advertising Protocol) - Advertises network services.
 NLSP (Netware Link Services Protocol) - Link state routing protocol.
 GNS (Get Nearest Server) - A type of SAP advertisement used to locate a server for client log-in.
Netware 2 - 3.11 (1983-1985)
Ethernet_802.3 (default encapsulation on Cisco routers) Cisco name novell-ether. Also called Ethernet raw.
Netware 3.12 - 4.x (1985 - )
Ethernet_802.2 Cisco name sap (service access points) This is standard IEEE format and includes LLC header.
Ethernet_II uses TCP/IP Cisco name arpa. Novell 5.0 onwards uses TCP/IP instead of IPX.
Cisco name snap (Subnetwork Access Protocol)

Default Encapulations
 Ethernet - novell-ether
 Token Ring - sap
 FDDI - snap

Novell IPX RIP
 Incompatible with IP RIP.
 2 Metrics used (Hops, Ticks).
 Max hop count 15.
 Updates every 60 sec.
 Not efficient for large networks

IPX and Cisco routers
 Cisco routers maintain routing tables for each IPX protocol enabled on the network.
 Routers can provide network-based LAN sharing on IPX server-less LAN segments.
 Each network address must use a distinct IPX encapsulation.
 Subinterfaces on routers are used to assign multiple network numbers and encapsulations on single interfaces.

IPX IOS Router Configuration
Router(config)# ipx routing
Router(config)# ipx maximum paths x (default 1, max 512)
Router(config)# int e0.1
Router(config-if)# encapsulation novell-ether
Router(config-if)# ipx network 9e
ipx delay - used to manually set the tick metric delay on an interface. Default values for interface delays are LAN = 1 tick, WAN = 6 ticks.

Router IPX Troubleshooting
Show ipx interface - status / parameters (IPX RIP and SAP info)
Show ipx route - routing table
Show ipx servers - server list)
Show ipx traffic - number / type of packets
Show protocol - IPX address of an interface
Debug ipx routing activity - info on RIP updates
Debug ipx sap - info on Sap updates

SAP Service Advertising Protocols
 4 - Netware File Server
 7 - Print Server
 24 - Remote bridge server (router)

 SAP packets sent every 60 seconds.
 Routers build SAP tables.
 Routers only respond to GNS requests when servers are not local.


Access Control Lists are used to:
 Prioritise traffic
 Restrict or reduce updates
 Provide basic security
 Block types of traffic

Access control list placement
 Standard ACLs - Place as close to destination as possible.
 Extended ACLs - Place as close to source of traffic as possible.
 Only one ACL per port per direction is allowed.
 ACL are more efficient on outbound port.
 If a packet does not match the ACL statement then it will be implicitly denied.
 Once a packet matches an ACL statement no other checks are made, it is permitted.

Standard ACLs - Used to permit or deny an entire protocol suite.
The following two statements have the same effect:
Router(config)# access-list 1 permit
Router(config)# access-list 1 permit any
The following two statements also have the same effect:
Router(config)# access-list 1 permit
Router(config)# access-list 1 permit host

Extended ACLs - Used to permit or deny specific protocols
Protocol ranges are used in ACL statements to deny specific protocols. Below are the ones you will need for your CCNA.

Protocol Range
IP 1-99
Extended IP 100-199
Appletalk 600-699
IPX 800-899
Extended IPX 900-999
IPX SAP 1000-1099

Use the following table to permit or deny specific protocols, ports or ranges of port numbers, an example ACL follows.

lt Less than
gt Greater than
neq Not equal to
eq Equal to

Router(config)# access-list 101 deny tcp any eq 23
Router(config)# access-list 101 permit ip any any established - Established keyword used to connect with a TCP established connection.

Named ACLs
Named access control lists are another way of creating ACLs, any example follows.
Router(config)# ip access-list standard Nik
Router(config std-nacl)# deny any log - used to deny log packets.

Viewing ACLs
Router(config)# show access-lists - shows all access lists.
Router(config)# show access-list 101 - shows access list 101.
Router(config)# show ip interface - used to find out which access lists are on which interfaces.

Configuring ACLs on an interface
Router(config)# interface s1
Router(config-if)# ip access-group 1 out /in - out bound is the default.

Removal of ACLs
Router(config)# no access-list 1


Internetwork Packet Exchange (IPX) is a legacy network protocol used by the Novell NetWare operating systems to route packets through an internetwork. IPX is a datagram protocol used for connectionless communications - similar to IP (Internet Protocol) in the TCP/IP suite. Higher-level protocols, such as SPX and NCP, are used for additional error recovery services.
To make best-path routing decisions, IPX uses the services of a dynamic distance vector routing protocol such as Routing Information Protocol [RIP ]) or NetWare Link-State Protocol [NLSP]).
Novell IPX network addresses are unique and are represented in hexadecimal format that consist of two parts: a network number and a node number. The IPX network number, which is assigned by the network administrator, is 32 bits long. The node number, which usually is the Media Access Control (MAC) address for one of the system's network interface cards (NICs), is 48 bits long. IPX's use of a MAC address for the node number enables the system to send nodes to predict what MAC address to use on a data link.

Novell NetWare IPX supports four encapsulation schemes on a single router interface:
• Novell Proprietary- Also called 802.3 raw or Novell Ethernet_802.3, Novell proprietary serves as the initial encapsulation scheme that Novell uses.
• 802.3- Also called Novell_802.2, 802.3 is the standard IEEE 802.3 frame format.

• Ethernet version 2- Also called Ethernet-II or ARPA, Ethernet version 2 includes the standard Ethernet Version 2 header, which consists of Destination and Source Address fields followed by an EtherType field.
• SNAP- Also called Ethernet_SNAP, SNAP extends the IEEE 802.2 header by providing a type code similar to that defined in the Ethernet version 2 specification.
The maximum length of the data section of an IPX packet varies from a minimum of 30 bytes (the header only) depending on the lower layer MAC protocol (Ethernet or token ring) that is being used.

TCP/IP Quick Guide: A comprehensive pocket and quick reference for people who are learning and using TCP/IP.

Networking 2006 - A Calendar exclusively designed for IT/Networking Pros.

Protocol Structure - Novell IPX: Internetwork Packet Exchange Packet Header

The NetWare IPX Packet Header:
8 16bit
Packet Length
Transport control Packet Type
Destination Network (4 bytes)
Destination node (6 bytes)
Destination socket (2 bytes)
Source network (4 bytes)
Source node (6 bytes)
Source socket (2 bytes)

• Checksum- Indicates that the checksum is not used when this 16-bit field is set to 1s (FFFF).
• Packet length- Specifies the length, in bytes, of a complete IPX datagram. IPX packets can be any length, up to the media maximum transmission unit (MTU) size (no packet fragmentation allowed).
• Transport control- Indicates the number of routers through which the packet has passed. When this value reaches 16, the packet is discarded under the assumption that a routing loop might be occurring.
• Packet type- Specifies which upper-layer protocol should receive the packet's information. It has two common values:
o 5- Specifies Sequenced Packet Exchange (SPX)
o 17- Specifies NetWare Core Protocol (NCP)
• Destination network, Destination node, and Destination socket- Specify destination information.
• Source network, Source node, and Source socket- Specify source information.

Related Protocols
IP , IPv6 , NetWare , SPX , RIP , NLSP

Sponsor Source
IPX is a Novell protocol.

Reference IPX Structure : NetWare Protocols



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