CCNA Facts

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CCNA 1 -- Net Fun

Confreg -- Configuration Register

Default 0x2102

rommon 1> confreg 0x2142                 - disable startup-config
rommon 2> reset

copy startup running
conf t 
 enable secret cisco
 line con 0
   password cisco
router(conf)# config-register 0x2102     - enable startup-config


  • Putty: Ctrl-Break sends break-signal   Source: putty-wishlist       OR right-click on the header of putty / Special Commands / Break.
  • TeraTERM: Control-menu -> Send break (sometimes Alt-B) standard break-key sequences

PDU: Ethernet

min 64 bytes max 1522 (was 1518 before VLAN's)
(From CCNA1 9.3.1)


PDU: PPP - Point-to-pint protocol

(from 2.2.5 ccna4) LCP Packet Codes:

LCP Code: LCP Packet Type: Description:
1 Configure-Request. Sent to open or reset a P P P connection. Configure-Request contains a list of LCP options with changes to default option values.
2 Configure-Ack. Description: Sent when all the values of all the LCP options in the last Configure-Request received are recognized and acceptable. When both P P P peers send and receive Configure-Acks, the LCP negotiation is complete.
3 Configure-Nack. Sent when all the LCP options are recognized, but the values of some options are not acceptable. Configure-Nack includes the offending options and their acceptable values.
4 Configure-Reject. Description: Sent when LCP options are not recognized or not acceptable for negotiation. Configure-Reject includes the unrecognized or non-negotiable options.
5 Terminate-Request. Optionally sent to close the P P P connection.
6 Terminate-Ack. Sent in response to the Terminate-Request.
7 Code-Reject. Sent when the LCP code is unknown. The Code-Reject message includes the offending LCP packet.
8 Protocol-Reject. Sent when the P P P frame contains an unknown Protocol ID. The Protocol-Reject message includes the offending LCP packet. Protocol-Reject is typically sent by a P P P peer in response to a P P P NCP for a LAN protocol not enabled on the P P P peer.
9 Echo-Request. Optionally sent to test the P P P connection.
10 Echo-Reply. Sent in response to an Echo-Request. The P P P Echo-Request and Echo-Reply are not related to the ICMP Echo Request and Echo Reply messages.
11 Discard-Request. Optionally sent to exercise the link in the outbound direction.

 PPP Configuration Options (from 2.3.1 CCNA4)
 Authentication, Compression (Stacker/Predictor), Error detection, Multilink, PPP Callback

PDU: Frame-Relay

TCP and UDP ports

 21 FTP-control (20 ftp data)
 22 SSH
 23 Telnet
 25 Mail (SMTP)
 53 DNS (UDP för frågor, TCP för databasöverföringar)
143 IMAP


MUA etc ...

Subnetting Numbers

/24  254 usable addresses
/25    .128            126 usable addresses
/26    .192             62 usable addresses
/27    .224             30 usable addresses
/28    .240             14 usable addresses
/29    .248              6 
/30    .252              2
/31    .254              0
/32    .255              0 slash->mask (user:cisco, pass:cisco)

CCNA 2 -- Routing

RFC1918 name IP address range number of addresses classful description largest CIDR block (subnet mask) host id size
24-bit block - 16,777,216 single class A network ( 24 bits
20-bit block - 1,048,576 16 contiguous class B network ( 20 bits
16-bit block - 65,536 256 contiguous class C network ( 16 bits

Table: Routing Protocol Comparizon

Administrative Distance 120 120 90
170 for external (ie default-route)
110 eBGP 20
iBGP 200
Class Classful Classless Classless Classless Classless
Default Route ip route DEST
Default-information originate
ip route DEST
Default-information originate
ip route DEST
redistribute static
ip route DEST
Default-information originate
Send Address
All OSPF Routers
All DR Routers
Packet type RIP-UDP-IP
UDP har protocol nr 17
RTP protocol nr 88 (dec)
OSPF has IP protocol nr 89
prot# 6
Must Match AS# = Proces ID (9.2.2)
K-value mismatch (unconfirmed)
Subnet-mask (src: blog !!)
Area ID
Timers (HELLO etc)

Network-type (included??)
Stub Flag
MTU (this can be overridden though)
Subnet-mask (unless on point-to-point link, or virtual-link)

Timers Update 30s
Invalid 180s (route reatined)
Flush 240s (R. deleted)
Holddown 180s
RIP_JITTER -0% - -15%
>T1: 5 secs HELLOs
<=T1: 60 secs HELLOs
HoldTime = 3xHELLO
DeadTimer= 4xHELLO
Spezials no auto-summary !!
-if)# ip sum-addr eigrp 100
-if)# ip bandwidth-perc eigrp AS# %%
loopback-if)# ip ospf network-type point-to-point
Security  ? ip rip authentication key-chain NAME
ip rip authentication mode { text ¦ md5 }
-if)# ip authentication mode eigrp <AS> md5
-if)# ip authentication key-chain eigrp <AS> <key-chain>
-if)# ip ospf authentication message-digest
-if)# ip ospf message-digest-key 1 md5 FooBar

OSPF cost

In general, the path cost is calculated using the following formula:

10^8 ÷ Bandwidth

Using this formula, the default path costs were calculated as noted in the following list. If these values do not suit your network, you can use your own method of calculating path costs.

Link Type OSPF Cost
•56-kbps serial link Default cost is 1785
•64-kbps serial link Default cost is 1562
•T1 (1.544-Mbps serial link) Default cost is 65
•E1 (2.048-Mbps serial link) Default cost is 48
•4-Mbps Token Ring Default cost is 25
•Ethernet Default cost is 10
•16-Mbps Token Ring Default cost is 6
•FDDI Default cost is 1

more more

CCNA 3 -- Switching + Wireless

Encryption types

 Type 0, which is a cleartext password,                     cisco
 type 5, MD5 Message Digest 5,                              $1$iUjJ$cDZ03KKGh7mHfX2RSbDqP.
 Type 7, which uses the algorithm from the Vigenère cipher  07362E590E1B1C041B1E124C0A2F2E206832752E1A01134D


802.1D common spanning tree
802.1w RSTP
802.2 LLC (not commonly used, mainly Novell)
802.3   Ethernet
802.3af PoE
802.5   TokenRing
802.15.3 PAN: Bluetooth
802.11   LAN
802.11   MAN: 
802.16   MAN:  IEEE WirelessMAN
802.20   MAN:  Mobile Broadband Wireless Access (MBWA)
CDMA          Code division multiple access
802.11a  54Mb/s  5 Ghz    OFDM                             Range:  35 meter=150feet   23 non overlapping channels
802.11b  11Mb/s  2.4 GHz  DSSS= 1, 2, 5.5, 11MB/s                  35 meter            3 non overlapping channels (ch1, Ch6, Ch11) 11channels in EU, 13 in US 
802.11i  = WPA2  * AES Encryption,  * 802.1x Authentication,  * Dynamic key management,  * WPA2 is the Wi-Fi Alliance's implementation of 802.11i


802.11g  54Mb/s  2.4 GHz  OFDM= 6, 9, 12, 18, 24, 48, 54Mb/s       35 meter            3 non overlapping channels
802.11n 248Mb/s theoretical max (?)                                70 meter=230feet

IBSS Independent BSS = ingen accesspunkt; kallas ad-hoc
BSS Basic Service Set = En accesspunkt
ESS Extended Service Set = Flera accesspunkter i samma trådade nätverk, should have 15% overlap
JoinProcess(association)=1:Probing, 2:Authentication, 3:Association

Table: [ Common | Rapid | Multiple ] Spanning Tree Comparizon

Question Common STP Rapid STP MSTP x y z

States Blocking XX sec
Listening 15 sec
Learning 15 sec
. .
Default Values
BridgePrio 32768
PortPri      128
Hello Time     2 sec  
Max Age       20 sec  
Forward Delay 15 sec
root primary   -4096
root secondary=28672
BridgePrioSteps 4096
Topology Change TCA and TCN

yada yada

STP link costs (IEEE)

Link Speed Cost (Revised IEEE) Cost (Previous IEEE)
10Gb/s 2 1
1Gb/s 4 1
100Mb/s 19 10
10 Mb/s 100 100


Ethernet frames with a value of 1 in the least-significant bit of the first octet<ref group=note>On Ethernet, the least-significant bit of an octet is the first to be transmitted. A multicast is indicated by the first transmitted bit of the destination address being 1.</ref> of the destination address are treated as multicast frames and are flooded to all points on the network. While frames with ones in all bits of the destination address (FF:FF:FF:FF:FF:FF) are sometimes referred to as broadcasts, Ethernet network equipment generally does not distinguish between multicast and broadcast frames. Modern Ethernet controllers filter received packets to reduce CPU load, by looking up the hash of a multicast destination address in a table, initialized by software, which controls whether a multicast packet is dropped or fully received.

Some well known Ethernet multicast addresses<ref>Template:Cite web</ref>
Ethernet multicast address Type Field Usage
01-00-0C-CC-CC-CC 0x0802 [[1]] (Cisco Discovery Protocol), VTP (VLAN Trunking Protocol)
01-00-0C-CC-CC-CD 0x0802 Cisco Shared Spanning Tree Protocol Address
01-80-C2-00-00-00 0x0802 Spanning Tree Protocol (for bridges) IEEE 802.1D
01-80-C2-00-00-08 0x0802 Spanning Tree Protocol (for provider bridges) IEEE 802.1AD
01-80-C2-00-00-02 0x8809 Ethernet OAM Protocol IEEE 802.3ah (A.K.A. "slow protocols")
01-00-5E-xx-xx-xx 0x0800 IPv4 Multicast (RFC 1112)
33-33-xx-xx-xx-xx 0x86DD IPv6 Multicast (RFC 2464)


 WEP  Wired Equivalent Privacy
 WPA  Wi-Fi Protected Access
 TKIP Temporal Key Integrity Protocol (based on same cipher as WEP; RC4 ) 
         DES is a symmetric cryptographic algorithm,
         RSA is an asymmetric (or public key)
 AES Advanced Encryption Standard
 PSK or PSK2 with TKIP is the same as WPA
 PSK or PSK2 with AES is the same as WPA2
 EAP Advanced Encryption Standard, assumes protected channel for setup, [i.e. password sent unprotected /Robert ]
 PEAP Protected EAP - uses Transport Layer Security (TLS) [TLS predecessor is SSL]
 LEAP Atentication similar to WEP, cisco propr. protocol

Cisco's response to the weaknesses of LEAP suggests that network administrators either force users to have stronger, more complicated passwords or move to another authentication protocol also developed by Cisco, EAP-FAST, to ensure security.

 EAP-FAST  Flexible Authentication via Secure Tunneling   (Wikipedia: EAP-*)


Frame Relay

 Encapsulation frame-relay [ cisco | ietf ]
 Frame-relay map ip 102 broadcast cisco

Three incompatible LMI-types: cisco, ansi & q933a (default= router autosenses FR-switch's LMI-type

 frame-relay lmi-type [ cisco | ietf | q933a ]
 keepalive 10    <-- Default


0 - 15, 992 - 1023   DEFINED
1023 LMI (cisco)
8 bits 16 bits 8 bits 8 bits 8 bits 8 bits Variable 16 bits 8 bits
Flag LMI DLCI Unnumbered IE Protocol Descriminator Call Reference Message Types IEs FCS Flag

IE=Information Element

Network discovery

 cnap-brouter3560#show ip route
 Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
        D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
        N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
        E1 - OSPF external type 1, E2 - OSPF external type 2
        i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
        ia - IS-IS inter area, * - candidate default, U - per-user static route
        o - ODR, P - periodic downloaded static route
 Gateway of last resort is to network 

 O [110/2] via, 7w0d, GigabitEthernet0/1
 O [110/2] via, 7w0d, GigabitEthernet0/1
 C is directly connected, Vlan28
 O [110/2] via, 7w0d, GigabitEthernet0/1
 O [110/2] via, 7w0d, GigabitEthernet0/1
 O [110/2] via, 7w0d, GigabitEthernet0/1
 C is directly connected, Vlan25 is subnetted, 3 subnets
 O [110/2] via, 7w0d, GigabitEthernet0/1
 O [110/2] via, 7w0d, GigabitEthernet0/1
 O [110/2] via, 7w0d, GigabitEthernet0/1 is subnetted, 1 subnets
 O E2 [110/20] via, 7w0d, GigabitEthernet0/1
 C is directly connected, Vlan24
cnap-brouter3560#show cdp neighbors
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
                  S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone

Device ID        Local Intrfce     Holdtme    Capability  Platform  Port ID
                 Gig 0/5           144           S I      WS-C2950T Gig 0/2
                 Gig 0/9           122           S I      WS-C2960S Gig 1/0/24
                 Gig 0/3           140           S I      WS-C2950T Gig 0/2
                 Gig 0/13          142           S I      WS-C2950T Gig 0/2
                 Gig 0/11          123           S I      WS-C2950T Gig 0/2
                 Gig 0/7           141           S I      WS-C3560- Fas 0/24
                 Gig 0/8           152           S I      WS-C2960- Gig 0/2
Switch           Gig 0/4           170           S I      WS-C2950- Fas 0/12
                 Gig 0/28          179           S I      WS-C2960G Gig 0/24
                 Gig 0/24          154           S I      WS-C2960G Gig 0/24

Device ID        Local Intrfce     Holdtme    Capability  Platform  Port ID
                 Gig 0/23          146           S I      WS-C2960G Gig 0/23
                 Gig 0/22          144           S I      WS-C2960G Gig 0/22
                 Gig 0/21          141           S I      WS-C2960G Gig 0/21  Gig 0/1           158           S I      WS-C2960G Gig 0/39
b005             Gig 0/15          148           S I      WS-C2950T Gig 0/2
                 Gig 0/2           147          R S I     2801      Fas 0/0

cnap-brouter3560#show cdp neighbors detail
Device ID:
Entry address(es):
  IP address:
Platform: cisco WS-C2950T-24,  Capabilities: Switch IGMP
Interface: GigabitEthernet0/5,  Port ID (outgoing port): GigabitEthernet0/2
Holdtime : 158 sec

Version :
Cisco Internetwork Operating System Software
IOS (tm) C2950 Software (C2950-I6K2L2Q4-M), Version 12.1(22)EA9, RELEASE SOFTWARE (fc1)
Copyright (c) 1986-2006 by cisco Systems, Inc.
Compiled Fri 01-Dec-06 18:22 by weiliu

advertisement version: 2
Protocol Hello:  OUI=0x00000C, Protocol ID=0x0112; payload len=27, value=00000000FFFFFFFF010221FF000000000000000BFD37B580FF0000
VTP Management Domain: 'cnap'
Native VLAN: 42
Duplex: full
Management address(es):
  IP address:

Device ID:
Entry address(es):
  IP address:
Platform: Cisco 2801,  Capabilities: '''Router''' Switch IGMP
Interface: GigabitEthernet0/2,  Port ID (outgoing port): FastEthernet0/0
Holdtime : 97 sec

Version :
Cisco IOS Software, 2801 Software (C2801-IPVOICEK9-M), Version 15.1(3)T, RELEASE SOFTWARE (fc1)
Technical Support:
Copyright (c) 1986-2010 by Cisco Systems, Inc.
Compiled Mon 15-Nov-10 22:20 by prod_rel_team

advertisement version: 2
VTP Management Domain: ''
Duplex: full
Management address(es):
Device ID:
Entry address(es):
  IP address:
Platform: cisco WS-C2960G-48TC-L,  Capabilities: Switch IGMP
Interface: GigabitEthernet0/1,  Port ID (outgoing port): GigabitEthernet0/39
Holdtime : 43 sec

Version :
Cisco IOS Software, C2960 Software (C2960-LANBASEK9-M), Version 12.2(44)SE, RELEASE SOFTWARE (fc1)
Copyright (c) 1986-2008 by Cisco Systems, Inc.
Compiled Sat 05-Jan-08 00:42 by weiliu

advertisement version: 2
Protocol Hello:  OUI=0x00000C, Protocol ID=0x0112; payload len=27, value=00000000FFFFFFFF010221FF000000000000001B8F7F7500FF0000
VTP Management Domain: 'HV'
Native VLAN: 755
Duplex: full
Management address(es):
  IP address:

X: Orientation Course


 ::  AC Tutorials
 ::  Academy Marketplace
 ::  Certifications and Vouchers
 ::  Course Catalog                -- Offered courses and Eagle Server
                                      CCNA Exploration --> Scope and Sequence 
 ::  Course Materials              -- Curriculum and Assessments(Chapter test questions)
 ::  Equipment Information         -- Lab Equipment List & Contact Info 
                                      Remote Access and BDL Solutions 
                                      Interactive Learning Tools ( = link to packet tracer )
                                      Maintenance Service and Support --> "Image & Hardware Support","IOS Download Guide",SignUp Process"
 ::  File Sharing
 ::  Glossary
 ::  Library                       -- Länkar till saker som finns i de andra rubrikerna... ?!?
 ::  Marketing Toolkit             --> Collateral/Media --> Logos --> Cisco Networking Academy Identity Guide
                                                                      Cisco Networking Academy Partner Logo ->
 ::  Support Desk                  --> Academy, Assessment, and Curriculum Quality Support (also click "HELP"; top right corner)
 ::  Tools        -> /Curriculum\ /Course\ /ClassroomSetup\ 
 ::  Academy Netspace Games
 ::  Facebook
 ::  Club NetAcad
Career Opportunities

AC Tutorials

  • Academy Management: Administrators (Legal Main Contact, Curriculum Lead)
  • User Management: Instructors and Administrators
  • Teaching / learning: Instructors
  • Assessment Management: Instructors
  • Community: All users
  • Support: All users


  • CCNA Exploration 4.0 "Network Fundamentals" Pacing Guide (2008). Klick Library->InstructorResources->ccnaExpl:Net Fun->Pacing Guide
  • CCNA Exploration Scope and Sequence         Klick Course Catalog -> CCNA Exploration -> Scope and Sequence
  • Quality Assurance Plan (QAP)         Deleted according to Jaskaran /Robert
  • Networking Academy Maintenance - Image & Hardware Support         klick ::Equipment Information -> Lab Equipment List & ...
            OR ::Library -> Equipment Information -> Lab Equipment List & ...


8.4.2 The Show IP Route Challange Lab

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