Term | Definition |
Four Router Functions | Packet switching, Packet filtering, Internetwork communication, Path selection |
7 Layers of OSI Model | Application, Presentation, Session, Transport, Network, Data Link, Physical |
Application Layer | User interface. File, print, message, database, and applications. |
Presentation Layer | Data encryption, compression, and TRANSLATION. |
Session Layer | Separates data of each application. Dialog control |
Transport Layer | Provides reliable or unreliable delivery, and performs error correction before retransmit. End-to-end control. Segments |
Network Layer | Logical addressing for use in path selection, ROUTING. Packets. |
Data Link Layer | Access to media via MAC address. Also performs error detection. Frames |
Physical Layer | Voltage, wire speed, and pinout of cables. Bits |
Flow Control | Ensure data integrity at the Transport layer. Segments delivered are ack'd back to the sender, retransmit not ack'd. Sequenced segments reconstructed. |
Windowing | The size of the window controls how much information is transferred from one end to the other before an ack is required. |
Metric | The distance to the remote network. |
CSU | Channel Service Unit |
DSU | Data Service Unit |
DTE | Data Terminal Equipment |
DCE | Data Communication Equipment |
Collision Domain | Where one device sends a frame out on a physical network segment forcing every other device on the same segment to pay attention to it. |
Hub | One collision domain. One broadcast domain. HALF DUPLEX |
Switch | One collision domain on each port. One broadcast domain by default, which can be changed with vlans. |
CSMA/CD | Carrier Sense Multiple Access with Collision Detection. Prevents devices from transmitting simultaneously on the same network medium. |
Full Duplex | Talking in both directions at the same time. |
Half Duplex | Talking in one direction at a time. |
MAC Address | 48 bits. 24 (6 characters) OUI number, 24 vendor specific. |
Nibble Values | 8 4 2 1 |
Byte Values | 128 64 32 16 8 4 2 1 |
1 | 00000001 |
2 | 00000010 |
4 | 00000100 |
8 | 00001000 |
16 | 00010000 |
32 | 00100000 |
64 | 01000000 |
128 | 10000000 |
192 | 11000000 |
224 | 11100000 |
240 | 11110000 |
248 | 11111000 |
252 | 11111100 |
254 | 11111110 |
255 | 11111111 |
0 | 0000 |
1 | 0001 |
2 | 0010 |
3 | 0011 |
4 | 0100 |
5 | 0101 |
6 | 0110 |
7 | 0111 |
8 | 1000 |
9 | 1001 |
A, 10 | 1010 |
B, 11 | 1011 |
C, 12 | 1100 |
D, 13 | 1101 |
E, 14 | 1110 |
F, 15 | 1111 |
Frame Encapsulation | Destination address, source address, data, FCS |
802.3 | 10Base-T |
802.3u | 100Base-TX |
802.3u | 100Base-FX (fiber) |
802.3z | 1000Base-SX (multimode fiber) |
802.3z | 1000Base-LX (single-mode L = LONE fiber) |
802.3.an | 10GBase-T |
Straight-through cable | Host to switch or hub, router to switch or hub. Four wires used - 1, 2, 3, and 6 |
Crossover cable | 1 - 3, 2 - 6 |
Rollover cable | 1-8,2-7,3-6,4-5 |
Fiber optic cable | Core, cladding, buffer |
TCP | Transmission Control Protocol. Takes large blocks of info from an app and breaks them into segments. |
IP | Internet Protocol |
Telnet | Uses TCP, sent in clear text |
SSH | Secure Shell. Uses TCP, encrypted |
FTP | File Transfer Protocol. A program operating as a protocol |
TFTP | Trivial File Transfer Protocol. Stripped down version of FTP. |
SNMP | Simple Network Management Protocol. Collects and manipulates network information from an NMS. |
NMS | Network Management Station. |
HTTP | Hypertext Transfer Protocol. The web server is found, then the page is requested, and the page information is sent back to the host. |
NTP | Network Time Protocol. Time is updated from an NTP server. THIS HELPS WITH TROUBLESHOOTING via a time stamp. |
DNS | Domain Name Service. Resolves host names/internet names to ip addresses. |
DHCP | Dynamic Host Control Protocol. Assigns ip addresses to hosts. DHCPDiscover, DHCPOffer, DHCPRequest, DHCPAck |
APIPA | Automatic Private IP Addressing. 169.254.0.1-169.254.255.254 255.255.0.0
Host assigns itself then you're network is down. |
UDP | User Datagram Protocol. Thin protocol, faster than TCP, but less reliable. |
ARP | Address Resolution Protocol. Finds the hardware address of a host from a known ip address. |
Bit | One digit, a 1 or a 0. |
Byte | Typically 8 bits. |
Octet | 8 bits. |
Network address | The primary address of a network. |
Broadcast address | The address used to send info to all hosts in a network. |
Class A Address | 0 - 127 |
Class B Address | 128 - 191 |
Class C Address | 192 - 223 |
Address Class A | 10.0.0.0 - 10.255.255.255 |
Address Class B | 172.16.0.0 - 172.31.255.255 |
Address Class C | 192.168.0.0 - 192.168.255.255 |
Layer 2 Broadcast | ff:ff:ff:ff:ff:ff |
Loopback Address | 127.0.0.1 Can be any address 127.0.0.1 - 127.255.255.254 |
VLSM | Variable Length Subnet Mask. When your subnet mask does not match your typical address class (classless). example: 10.20.0.0 255.255.0.0 |
Summarization | Allows routers to advertise many networks with one address. |
User exec mode | Limited to basic monitoring commands. |
Privileged exec mode | Provides access to all other router commands. |
Global configuration mode | Commands that affect the entire system. |
Specific configuration modes | Commands that affect interfaces/processes only. |
Setup mode | Interactive configuration dialog. |
hostname | (config)#hostname myrouter |
banner motd | Message you see when you log in. |
Setting up SSH | A domain name is required to configure this.
(config)# ip domain-name mypage.int
(config)# username admin password mypass
(config)# crypto key generate rsa |
Setting up SSH (more) | (config)# ip ssh version 2
(config)# line vty 0 4
(config)# transport input ssh telnet |
Service password-encryption | Encrypts any passwords you configure after this is submitted. |
How to enable an interface? | no shutdown |
Secondary ip address | ip address 192.168.0.1 255.255.255.0 secondary |
Finding stuff | show run | include 192.168.0
show run | begin access |
Serial Interface | The DCE end must be configured with a clock rate.
(config)# clock rate 64000 |
Saving your changes to memory | copy running-config startup-config |
Deleting the startup config | erase startup-config (then reload) |
Clearing counters on an interface | router#clear counters fa0/0 |
No buffer | You don't have any buffer room left for incoming packets. |
Ignored | If packet buffers are full, packets will be dropped. Increments with no buffer. |
Runts | Frames that didn't meet the minimum frame size of 64 bytes. Typically caused by collisions. |
Giants | Frames larger than 1518 bytes. |
Late collisions | This increments with duplex mismatch. |
Bootstrap | stored in ROM. Boots the router up and loads the IOS. |
POST | Power-on self-test. stored in the ROM. Checks the basic functionality of the router hardware and determines which interfaces are present. |
ROM monitor | rommon. used for troubleshooting and loads when the IOS in flash fails to load. |
RAM (cisco router) | used to hold packet buffers, ARP cache, routing tables, and also the software and data structures that allow the router to function. Running-config is stored in RAM. |
Flash Memory | Stores the Cisco IOS by default. Flash memory is not erased when the router is reloaded. |
NVRAM | Nonvolatile RAM. used to hold the router and switch configuration. NVRAM IS NOT ERASED WHEN THE ROUTER OR SWITCH IS RELOADED. |
Configuration register | used to control how the router boots up. Default is 0x2102. 0x2142 resets the router |
DHCP relay | ip helper-address 192.168.0.25 |
show ip dhcp binding | shows the status of any leased ip's to hosts |
show ip dhcp pool *poolname* | shows the range of ip's and stats of current ip leases. |
show ip dhcp server statistics | shows dhcp server stats |
show ip dhcp conflict | shows ip conflicts |
syslog server | logging host 192.168.0.25
service timestamps log datetime
ntp server 192.168.0.200 version 4 |
CDP | Cisco Discovery Protocol |
show ntp status | shows if the router is communicating with the ntp server. |
show ntp associations | shows the information about ntp. |
show cdp neighbor detail | shows a lot of details about neighboring devices. |
LLDP | Link Layer Discovery Protocol. IEEE version of CDP. |
show ip route | shows all the contents of the routing table. |
Static routing | Manually added routes |
Default routing | When a router only has one connection to other networks it is a stub router. All routes 0.0.0.0 0.0.0.0 to go to the next hop address. |
Dynamic routing | When protocols are used to find networks and update routing tables. |
AD | Administrative Distance. The distance a router lists for a route in the routing table. |
Connected Interface default AD | 0 |
Static route default AD | 1 |
EIGRP default AD | 90 |
OSPF default AD | 110 |
RIP default AD | 120 |
External EIGRP default AD | 170 |
Unknown default AD | 255 |
Distance Vector routing | Find the best path to a remote network based on distance. |
Link State routing | Find the best path to a remote network based on hop count. If a network is 16 hops away is is unreachable. |
Passive Interface | Preventing routing protocols from being sent out an interface that this is configured on. |
Switch interface | Any state other than up/up and it won't forward frames. |
administratively down/down | The interface is in shutdown. |
down/down | No cable plugged in, wrong cable pinouts, bad cable, the speeds are mismatched between devices. |
up/down | Check the other end, the interface may be misconfigured, shutdown, or the cable may not be seated properly. |
down/down (err-disabled) | Port security has disabled the interface |
solid amber light | The system has power, but is not functioning properly. |
solid green light | The system has power, but there's no current traffic. |
flashing green light | The link is up and passing traffic. |
flashing amber light | The port is blocked by spanning tree. |
Serial connection | 9600 baud, 8 data bits, 1 stop bits, parity none, flow control none. |
OSPF version 3 | Supports IPV6 |
ICMP version 6 | Supports IPV6 |
NDP | Neighbor Discovery Protocol. Works with IPV6 |
show mac address-table | shows the vlans that each mac address is in and what interface they are connected to. |
switchport security | switchport mode access
switchport port-security mac-address sticky
switchport port-security maximum 2 (1 is default)
switchport port-security violation shutdown |
VLAN | Virtual Local Area Network.
int fa0/2
switchport mode access
switchport access vlan 2 |
Three benefits of vlans | Broadcast control
Security
Flexibility/Scalability |
Voice vlan | The only option for more than one vlan to be assigned to a port. Otherwise, only one vlan per port. |
Trunk port | A way to transport multiple vlans between switches.
switchport trunk allowed vlan (all, 1-4) |
802.1q | IEEE method of frame tagging on a trunk port |
ISL | Inter-switch link. Proprietary to Cisco switches. |
show vlan | shows you all vlans, names, status, and ports. |
show int trunk | shows trunked ports, mode (on), encapsulation (802.1q), status (trunking), native vlan, and vlans allowed on each trunk port. |
Inter-vlan routing | int fa0/0.1
encapsulation dot1q 1
ip address 192.168.0.25 255.255.255.0
int fa0/0.2
encapsulation dot1q 2
ip address 192.168.1.25 255.255.255.0 |
Standard access list | Use only the source ip address as the condition test. 1-99, 1300-1999
access-list 10 permit 192.168.1.0 255.255.255.0
line vty 0 4
access-class 10 in |
Extended access list | Test based on source ip, destination ip, protocol field, and/or port number. 100-199, 2000-2699
access-list 110 deny tcp 192.168.0.128 0.0.0.127 host 10.1.1.254 eq 80
access-list 110 permit ip any any |
Named access list | Can be standard or extended.
ip access-list standard blockstudents
(config-std-nacl)#deny 10.1.1.0 0.0.0.255
(config-std-nacl)#permit any |
Inbound access list | Packets coming into the router are processed through the access lists before they can leave the router. |
Outbound access list | Packets are routed to the outbound interface and then processed through the access lists. |
remarks | (config-ext-nacl)#remark deny all students from faculty network |
show access-list | Displays all access lists and their settings |
show access-list 110 | Displays only the information for the list you selected, in this case access list 110. |
show ip access-list | shows only the ip access lists on the router. |
NAT | Network Address Translation |
Static NAT | One-to-one mapping of a private ip to/from a public ip.
ip nat inside source static 10.1.1.1 24.185.54.5 |
Dynamic NAT | Mapping of private ip's to/from a pool of public ip's.
ip nat pool students 24.185.54.1 24.185.54.7 255.255.255.248 |
Overloading (NAT) | Mapping of private ip's to/from a single public ip. (most common)
ip nat pool students 24.185.54.1 24.185.54.7 prefix-length 29
ip nat inside source list 7 pool students overload |
Inside local | Source host ip (private ip) |
Outside local | The address on the external interface of a router. Public ip |
Inside global | The address on the external interface of a router. Public ip |
Outside global | The address on the external interface of a router. Public ip |
IPV6 | 128 bits, first 48 bits global prefix, 16 bits subnet, last 64 bits interface id.
ipv6 address 2001:a9c:52d6:1::/64 eui-64 |
Global unicast addresses | 2000::/3 |
0:0:0:0:0:0:0:0 | ::. |
0:0:0:0:0:0:0:1 | ::1 |
0:0:0:0:0:0:192.168.0.25 | Mixed ipv4 in ipv6 format |
FC00::/7 | Unique local unicast range |
FE80::/10 | Link-local unicast range |
3FFF:FFFF::/32 | Reserved for examples and documentation |
2002::/16 | Used with 6-to-4 tunneling |
Root bridge | The switch with the lowest bridge id. |
Non-root bridge | All switches that are not the root bridge. |
BPDU | Bridge Protocol Data Unit. |
Bridge id | The bridge id is how STP keeps track of all the switches in the network. |
Port cost | Port cost determines the best path when multiple links are used between switches. The cost of a link is determined by the bandwidth of a link. |
Path cost | Port costs on the way to the root bridge are added together to equal path cost. |
Root port | The port with the lowest path cost to the root bridge. |
Designated port | A port that has been found to have the lowest cost. |
Non-designated port | Has a higher cost than the designated port. |
Forwarding port | Forwards frames and is either a root port or designated port. |
Blocked port | Won't forward frames, but listens to BPDU frames from neighbor switches. |
Listening port | Listens to BPDU's to prevent loops before forwarding frames. Does not populate the MAC address table. |
Learning port | Listens to BPDU's. Populates the MAC address table. |
Forwarding port | Sends and receives all frames. If the port is still a designated or root port at the end of the learning state it will go into forwarding state. |
Convergence | When all the ports have transitioned to either blocking or forwarding states. |
10Mbps cost | 100 |
100Mbps cost | 19 |
1000Mbps cost | 4 |
10,000Mbps cost | 2 |
IEEE 802.1d | The original STP standard. CST - Common Spanning Tree |
PVST+ | PER VLAN SPANNING TREE PLUS. Cisco propriety enhancement for STP with a separate 802.1d instance for each vlan. Multiple root bridges possible. |
IEEE 802.1w | Rapid Spanning Tree Protocol. One root bridge. |
Rapid PVST+ | Cisco version of RSTP. Separate instance per vlan. |
Spanning Tree Protocol | Root bridge is chosen based on bridge, the lowest bridge id wins. If the bridge id ties then the lowest priority number wins. If priority ties then lowest port number wins. |
Set STP Priority | spanning-tree vlan 10 priority 4096
spanning-tree vlan 10 root primary |
STP commands | show spanning-tree summary
show spanning-tree |
PortFast | Ports transition from blocking to forwarding immediately once the switch is turned on. Configured on a port for devices such as a server. |
PortFast commands | (config)#int range fa0/1
(config-if)#spanning-tree portfast |
BPDU Guard | Enable this on a port running portfast. If this port receives a BPDU the switch will place that port into error disabled (shutdown). Prevents a switch or hub from causing loops at access layer. |
BPDU Guard commands | (config)#spanning-tree portfast bpduguard default (sets this globally)
(config-if)#spanning-tree bpduguard enable |
EtherChannel | A way to bundle up to 8-100Mbps ports or 2-1000Mbps ports. |
EtherChannel configuration | Configure trunking on the ports first.
(config-if-range)#channel-group 1 mode active |
Cisco licensing | show license udi
router#license install flash:FTX67897976.lic
router#license save flash:your_license.lic |
FHRP | First Hop Redundancy Protocol. Using multiple routers to add redundancy by using a virtual ip and mac address for hosts to use as a gateway. One router as active and one as standby. |
HSRP | Hot Standby Router Protocol. Not load balancing. Virtual router as gateway. Active router, standby router, virtual router, and other routers that could be set as standby. |
HSRP MAC address | Includes 07.ac in the middle |
HSRP timers | Hello (3 seconds), hold (10 seconds), active (resets when hello arrives), and standby (resets when hello arrives. |
HSRP Group Roles | Virtual router: not physical. Active router: router that receives data sent to virtual router. Standby router: backup to active. |
HSRP configuration | (config)#int fa0/1
(config-if)#standby 10 ip 192.168.0.2
(config-if)#standby 10 name my_test
(config-if)#standby 10 priority 110 |
HSRP check settings | show standby
show standby brief |
HSRP Load Balancing | Can be done using different routers per vlan. |
VRRP | Virtual Router Redundancy Protocol. Multiple routers use a single virtual router. One router is the active, one is standby, the rest are listening. Active router is MASTER |
VRRP specifics | If a real ip is used that router is MASTER, if virtual ip is used then router with highest priority is MASTER. One MASTER, and one or more backup routers. Master uses vrrp messages to update status. |
VRRP Load Balancing | Shared between multiple virtual routers. |
GLBP | Gateway Load Balancing Protocol. Active/active. Multicast 224.0.0.102 UDP port 3222. |
GLBP load sharing | Traffic from LAN is shared by multiple routers. |
GLBP Multiple Virtual Routers | Up to 1024 virtual routers and 4 virtual forwarders per group. |
GLBP Configuration | (config-if)#glbp 10 ip 192.168.0.25
(config-if)#glbp name my-example
(config-if)#glbp priority 110 |
SYSLOG | debug 7, info 6, notify 5, warning 4, error 3, critical 2, alert 1, emergency 0 |
SYSLOG Configuration | (config)#logging trap notify
All results level 5 and lower will be logged. |
SNMPv2 | Supports plain text auth with MD5 or SHA. Can be configured for to use TCP. GET BULK |
SNMPv3 | Supports strong auth with MD5 or SHA with encryption DES or DES-256. Can use GET BULK and TCP. |
MIB | Management Information Base. A device where all the data is stored and organized. |
SNMP Configuration | (config)#snmp-server community backpack my_syslog_server rw |
NetFlow | Collects ip traffic info. Used for baselining, usage-based network billing, network design and planning, network security, and DOS/DDOS monitoring. |
NetFlow stats | Source/Destination ip's and ports, layer 3 protocol, TOS marking. |
NetFlow Configuration | (config-if)#ip flow ingress
(config-if)#ip flow egress
(config)#ip flow-export destination 192.168.0.25 8025
(config)#ip flow-export version 9
(config)#ip flow-export source loopback 25 |
Speed & Duplex Configuration | (config-if)#speed 100
(config-if)#duplex full |
CPE | Customer Premises Equipment. Owned by the customer and owned by them. |
Demarcation Point | Where the ISP responsibility ends. Usually a device (modem/router/switch) owned by the ISP in the customer's media closet. |
Local loop | Connects the demarc to the closest switching office (central office). |
Central Office | Also referred to as the POP (Point Of Presence) |
Toll network | A trunk line inside the ISP's network, made up of switches and facilities. |
Leased lines | Dedicated, point-to-point. From one CPE, through the ISP's network, to another CPE on the other side. |
Circuit switching | Shared link with other subscribers on the node, connection must be established first. Uses dial-up modems. |
Packet switching | Sharing bandwidth with other subscribers to save money. |
PPP | Point-to-Point Protocol. Can be used between different vendors. Allows auth and multiple connections over the asynchronous and synchronous links. Async connection = 10Mbps download/5Mbps upload. Sync connection = 10Mbps/10Mbps. |
MPLS | MultiProtocol Label Switching. Packets imposed with a label and then forwarded based on the label alone. |
ATM | Asynchronous Transfer Mode. Cells 53-bytes in length. |
DSL | Digital Subscriber Line. Symmetrical = download/upload speeds are the same. Asymmetrical = download/upload speeds are different. |
HDLC | High-level Data-Link Control. Default ppp encapsulation for Cisco routers over leased lines. |
LCP | Link Control Protocol. Possible settings: Authentication, Compression, Error detection, Multilink, PPP callback. |
PAP | Password Authentication Protocol. PPP authentication method that is only done during initial link connection. Passwords sent in clear text. |
CHAP | Challenge Handshake Authentication Protocol. Occasional checks are performed during the connection to verify hosts. |
CIR | Committed Information Rate. The promised data rate that a provider sets aside for a customer on a Frame Relay network. |
DLCI | Data Link Connection Identifiers. Identify PVC's in Frame Relay. Inverse ARP is used to map DLCI to an ip. |
LMI | Local Management Interface. Keepalive messages verify connectivity. |