This is a list of Cisco IOS commands and information. IOS is the software used on the vast majority of Cisco Systems routers and most Cisco network switches.
Privileged Mode
enable - get to privileged mode
disable - get to user mode
enable password <password_here> - sets privileged mode password
enable secret <password_here> - sets encrypted privileged mode password
Setting Passwords
enable secret <password_here> - set encrypted password for privilegedaccess
enable password <password_here> - set password for privileged access (used when there is no enable secret and when using older software)
Set password for console access:
(config)#line console 0
(config-line)#login
(config-line)#password <password_here>
Set password for virtual terminal (telnet) access (password must be set to
access router through telnet):
(config)#line vty 0 4
(config-line)#login
(config-line)#password <password_here>
Set password for auxiliary (modem) access:
(config)#line
aux 0
(config-line)#login
(config-line)#password <password_here>
Configuring the Router
sh running-config -
details the running configuration file (RAM)
sh startup-config -
displays the configuration stored in NVRAM
setup - Will start the the automatic setup; the same as when you first boot the router
config t - use to execute configuration
commands from the terminal
config mem - executes configuration commands
stored in NVRAM; copies startup-config to running-config
config net - used to retrieve configuration
info from a TFTP server
copy running-config startup-config
- copies saved config in running config (RAM) to NVRAM or "write memory" for IOS under ver.11
copy startup-config running-config - copies from non-volatile (NVRAM) to current running config (RAM)
boot system flash <filename_here> - tells router which IOS file in flash to boot from
boot system tftp - tells router which IOS file on the tftp server to boot from
boot system rom - tell router to boot from ROM at next boot
copy flash tftp - Copies flash to tftp server
copy tftp flash - Restores flash from tftp server
copy run tftp - Copies the current running-config to tftp server
copy tftp run - Restores the running-config from tftp server
General Commands
no shutdown
- (enables the interface)
reload - restarts the router
sh ver - Cisco IOS version, uptime of router, how the router started, where system was loaded from, the interfaces the POST found, and the
configuration register
sh clock - shows date and time on router
sh history - shows the history of your commands
sh debug - shows all debugging that is currently enabled
no debug all - turns off all debugging
sh users - shows users connected to router
sh protocols - shows which protocols are configured
banner motd # Your_message # - Set/change banner
hostname <router_name_here> - use to configure the hostname of the router
clear counters
- clear interface counters
Processes
& Statistics
sh processes - shows
active processes running on router
sh process cpu - shows cpu statistics
sh mem - shows memory statistics
sh flash - describes the flash memory and displays the size of files and the amount of free flash memory
sh buffers - displays statistics for router buffer pools; shows the size of the Small, Middle, Big,
Very Big, Large and Huge Buffers
sh stacks - shows reason for last reboot, monitors the stack use of processes and interrupts
routines
CDP Commands
(Cisco Discovery Protocol uses layer 2 multicast over a SNAP-capable link to send data):
sh cdp neighbor - shows directly connected neighbors
sh cdp int - shows which interfaces are running
CDP
sh cdp int eth 0/0 - show CDP info for specific interface
sh cdp entry <cdp_neighbor_here> - shows
CDP neighbor detail
cdp timer 120 - change how often CDP info is sent (default cdp timer is
60)
cp holdtime 240 - how long to wait before removing a CDP neighbor
(default CDP holdtime is 180)
sh cdp run - shows if CDP turned on
no cdp run - turns off CDP for entire router (global config)
no cdp enable - turns off CDP on specific interface
Miscellaneous
Commands
sh controller t1 - shows status of T1 lines
sh controller serial 1 - use to determine if DCE or DTE device
(config-if)#clock rate 6400
- set clock on DCE (bits per second)
(config-if)#bandwidth 64
- set bandwidth (kilobits)
IP Commands
Configure IP on an interface:
int serial 0
ip address 157.89.1.3 255.255.0.0
int eth 0
ip address 2008.1.1.4 255.255.255.0
Other IP Commands:
sh ip route
- view ip routing table
ip route <remote_network>
<mask> <default_gateway> [administrative_distance] -
configure a static IP route
ip route 0.0.0.0 0.0.0.0
<gateway_of_last_resort> - sets default gateway
ip classless - use with
static routing to allow packets destined for unrecognized subnets to use the
best possible route
sh
arp - view arp cache; shows MAC address of connected routers
ip address 2.2.2.2 255.255.255.0 secondary -
configure a 2nd ip address on an interface
sh ip protocol
sh ip interface - Show all IP interfaces
sh ip interface brief - Show brief overiew of IP interfaces
sh ip nat translations - Show current IP NAT translations
IPX Commands
Enable IPX on router:
ipx routing
Configure IPX + IPX-RIP on an int:
int ser 0
ipx network 4A
Other Commands:
sh ipx route
- shows IPX routing table
sh ipx int e0 - shows ipx address on int
sh ipx servers - shows SAP table
sh ipx traffic - view traffic statistics
debug ipx routing activity - debugs IPS RIP packets
debug ipx sap - debugs SAP packets
Routing
Protocols
Configure RIP:
router rip
network 157.89.0.0
network 208.1.1.0
Other RIP Commands:
debug ip rip - view
RIP debugging info
Configure IGRP:
router IGRP 200
network 157.89.0.0
network 208.1.1.0
Other IGRP Commands:
debug ip igrp events - view IGRP debugging info
debug ip igrp transactions - view IGRP debugging info
Access Lists
(see notes below for details)
sh ip int ser 0 -
use to view which IP access lists are applies to which int
sh ipx int ser 0 - use to view which IPX access lists are applies to which int
sh appletalk int ser 0 - use to view which AppleTalk access lists are applies to which int
View access lists:
sh access-lists
sh ip access-lists
sh ipx access-lists
sh appletalk access-lists
Apply standard IP access list to int eth 0:
access-list 1 deny 200.1.1.0 0.0.0.255
access-list 1 permit any
int eth 0
ip access-group 1 in
Apply Extended IP access list to int eth 0:
access-list 100 deny tcp host 1.1.1.1 host 2.2.2.2 eq 23
access-list 100 deny tcp 3.3.3.0 0.0.0.255 any eq 80
int eth 0
ip access-group 100 out
Apply Standard IPX access list to int eth 0:
access-list 800 deny 7a 8000
access-list 800 permit -1
int eth 0
ipx access-group 800 out
Apply Standard IPX access list to int eth 0:
access-list 900 deny sap any 3378 -1
access-list 900 permit sap any all -1
int eth 0
ipx access-group 900 out
Wan Configurations (see notes below for more details)
PPP Configuration
encapsulation ppp
ppp authentication <chap_or_pap_here>
ppp chap hostname <routername_here>
ppp pap sent-username <username_here>
sh int ser 0 - use to view encapsulation on the interface
Frame-Relay Configuration
encapsulation frame-relay ietf
- use IETF when setting up a frame-relay network between a Cisco router and a
non-Cisco router
frame-relay lmi-type ansi - LMI types are Cisco, ANSI, Q933A; Cisco is the
default; LMI type is auto-sensed in IOS v11.2 and up
frame-relay map ip 3.3.3.3 100 broadcast - if
inverse ARP won't work, map Other IP to Your DLCI # (local)
keepalive 10 - use to set keepalive
sh int ser 0 - use to show DLCI, LMI, and encapsulation info
sh frame-relay pvc - shows the configured DLCI's; shows PVC traffic stats
sh frame-relay map - shows route maps
sh frame-relay lmi - shows LMI info
Keyboard Shortcuts
CTRL-P - show previous command
CTRL-N - show next command
SHIFT-CTRL-6 - Break
Static
and Dynamic Routing
Static Routing - manually assigned by the Admin user entering the routes
(Routed Protocols - IP, IPX and AppleTalk)
Dynamic Routing - generated/determined by a Routing Protocol (Routing
Protocols - RIP I, RIP II, IGRP, EIGRP, OSPF, NLSP, RTMP)
Dynamic
1) With Dynamic Routing, routers pass information between each other so that routing tables are regularly maintained.
2) The routers then determine the correct paths packets should take to reach their destinations.
3) Information is passed only between routers.
4) A routing domain is called an Autonomous System, as it is a portion of the Internetwork under common admin authority.
5) Consists of routers that share information over the same protocol. Can be split into routing areas.
Distance Vector and Link-State Routing
Routing
Protocols
I) Interior (within an autonomous system - AS - group of routers under the same administrative authority)
a) Distance Vector - understands the direction and distance to any network connection on the internetwork. Knows how
many hops (the metric) to get there. All routers w/in the internetwork listen for messages from other routers, which are sent
every 30 to 90 seconds. They pass their entire routing tables. Uses hop count for measurement.
1) Used in smaller networks
that are have fewer than 100 routers.
2) Easy to configure and use.
3) As routers increase in number, you need to consider
CPU utilization, convergence time, and bandwidth utilization.
4) Convergence is due to routing updates at set intervals.
5) When
a router recognizes a change it updates the routing table and sends the whole table to all of its neighbors.
1) RIP - 15 hop count max
2) IGRP - 255 hop count max, uses reliability factor (255 optimal), and bandwidth
3) RTMP
b) Link State - understands the entire network, and does not use secondhand information. Routers exchange LSP?s (hello
packets). Each router builds a topographical view of the network, then uses SPF (shortest path first) algorithm to determine the
best route. Changes in topology can be sent out immediately, so convergence can be quicker. Uses Bandwidth,
congestion for measurement; Dijkstra's algorithm;
1) Maintains Topology Database.
2) Routers have formal neighbor relationship.
3) Exchanges LSA (Link State Advertisement) or
hello packets with directly connected interfaces.
4) These are exchanged at short intervals (typically 10 sec).
5) Only new info is
exchanged.
6) Scales well, however link?state protocols are more complex. 7) Requires
more processing power, memory, and bandwidth.
1) OSPF - decisions based on cost of route (metric limit of 65,535)
2) EIGRP - hybrid protocol (both Distance-Vector and Link State), Cisco proprietary
3) NLSP
4) IS-IS
II) Exterior
1) EGP (Exterior Gateway Protocol)
2) BGP (Border Gateway Protocol)
| Encapsulation | |
| 802.2 | sap |
| 802.3 | novell-ether |
| Ethernet II | arpa (Internet Standard) |
| Snap | snap |
Wan Service Providers
1) Customer premises equipment (CPE) - Devices physically located at subscriber?s
location; examples: CSU/DSU, modem, wiring on
the customer's location
2) Demarcation (or demarc) - The place where the CPE ends and the local loop portion of the service begins. (Usually in the "phone closet").
3) Local loop - Cabling from the demarc into the WAN service provider?s central
office; wiring from customer's location to the nearest CO
4) Central Office switch (CO) - Switching facility that provides the nearest point of presence for the provider?s WAN
service; location of telephone company's equipment where the
phone line connects to the high speed line (trunk); Regional Telco Office where the local loop terminates (the
Telco location nearest you)
5) Toll network - The switches and facilities, (trunks), inside the WAN provider?s "cloud."
DTE - the router side and receive clocking
DCE - the CSU/DSU side and provide clocking
WAN
Devices
Routers - Offer both internetwork and WAN interface controls
ATM Switches - High-speed cell switching between both LANs and WANs
X.25 and Frame-Relay Switches - Connect private data over public circuits using digital
signals
Modems - Connect private data over public telephone circuits
using analog signals
CSU/DSU (Channel Service Units/Data Service Units) - Customer Premises
Equipment (CPE) which is used to
terminate a digital circuit at the customer site
Communication Servers - Dial in/out servers that allow dialing in from remote
locations and attach to the LAN
Multiplexors - Device that allows more than one signal to be sent out
simultaneously over one physical circuit
ISDN BRI (Basic Rate Interface) - 2 64K B channels, plus 1 16K D channel
ISDN PRI (Primary Rate Interface) -
23 64K B channels, plus 1 64K D channel (North America & Japan),
30 64K B channels, plus 1 64K D channel (Europe & Australia)
Classful
and Classless Protocols
Classful - summarizes routing info by major
network numbers; ex. RIP,
IGRP
Classless - BGP, OSPF
Administrative Distances for IP
Routes
Administrative Distances are configured using ip route command:
Example: ip route 154.4.55.0 255.255.255.0 195.23.55.1 85 (where 85 is the administrative distance)
|
IP Route |
Administrative Distance |
|
Directly connected interface |
0 |
|
Static route using connected interface |
0 |
|
Static route using IP address |
1 |
|
EIGRP summary route |
5 |
|
External BGP route |
20 |
|
Internal EIGRP route |
90 |
|
IGRP route |
100 |
|
OSPF route |
110 |
|
IS-IS route |
115 |
|
RIP route |
120 |
|
EGP route |
140 |
|
External EIGRP route |
170 |
|
Internal BGP route |
200 |
|
Route of unknown origin |
255 |
Switching Terminology
Store-and-Forward ? copies entire frame into buffer, checks for CRC errors
before forwarding. Higher latency.
Cut-Through ? reads only the destination address into buffer, and forwards
immediately; Low latency; "wire-speed"
Fragment free ? modified form of cut-through; switch will read into the first 64 bytes before forwarding the frame. Collisions will usually occur within the first 64
bytes. (default for 1900 series).
| 1-99 | IP Standard Access List |
|---|---|
| 100-199 | IP Extended Access List |
| 200-299 | Protocol Type-code Access List |
| 300-399 | DECnet Access List |
| 600-699 | Appletalk Access List |
| 700-799 | 48-bit MAC Address Access List |
| 800-899 | IPX Standard Access List |
| 900-999 | IPX Extended Access List |
| 1000-1099 | IPX SAP Access List |
| 1100-1199 | Extended 48-bit MAC Address Access List |
| 1200-1299 | IPX Summary Address Access List |
| Access List | Filters | Wildcard Masks | Additional Notes |
|---|---|---|---|
| Standard IP | Source IP address field in the packet's IP header | To put simply, when the IP is broken down to binary, the 1's allow everything and the 0's must match exactly. | Wildcard mask examples: 0.0.0.0=entire address must match. 0.255.255.255=only the first octet must match, the rest will allow everything. 255.255.255.255=allow everything |
| Extended IP | Source IP or Destination IP, or TCP or UDP Source or Destination Ports, or Protocol | Same as standard | The key word ANY implies any IP value is allowed, the keyword HOST implies the IP exactly has to match |
| Standard IPX | Packets sent by clients and servers, and SAP updates sent by servers and routers | Configured as a hexadecimal number instead of binary | -1 means any and all network numbers ( works like ANY) |
| Extended IPX | Source Network or Node, or Destination Network or Node, or IPX Protocol, or IPX Socket, or SAP | Match multiple networks with one statement, again in hexadecimal | The most practical use of the protocol type is for NetBIOS |
| SAP | Sent and received SAP traffic | N/A | Updates its own SAP tables. Again uses -1 to mean "ANY" |
| ! | success |
| , | timeout |
| U | destination unreachable |
| ? | unknown packet type |
| & | TTL exceeded |
| !H | router rec'd, but didn't forward because of access-list |
| P | protocol unreachable |
| N | network unreachable |
| U | port unreachable |
| , | timeout |
Accessing
Router with Terminal Emulation
Using HyperTerminal on a Windows
machine adjust the following settings:
VT100 Emulation
Connection Speed: 9600 Baud
Data Bits: 8
Parity: None
Stop Bits: 1
Flow Control: None
On a Linux machine you may use Seyon or Minicom (at least one should come with
your distribution).
Router Startup Sequence
POST
Bootstrap program loaded from ROM
IOS is loaded from either flash (default), TFTP, or ROM
IOS image loaded into low-addressed memory; hardware and software is determined
Config file is load from NVRAM; if no configuration exists in NVRAM, the initial
configuration dialog will begin
Miscellaneous
Notes
Multiple Loop Problems ? complex topology can cause multiple loops to occur. Layer 2 has no mechanism to stop the loop. This is the main reason for Spanning ? Tree
Protocol.
Spanning-Tree Protocol (STP) IEEE 802.1d. ? developed to prevent routing
loops; uses STA (Spanning-Tree Algorithm) to calculate a loop-free network
topology; allows redundant paths without suffering the effects of loops in the
network
Virtual LAN?s (VLAN's) ? sets different ports on a switch to be part of different sub-networks. Some benefits: simplify moves, adds, changes; reduce administrative
costs; have better control of broadcasts; tighten security; and distribute load. Relocate the server into a secured location.
HDLC (High-Level Data Link Control) -
Link layer protocol for Serial links. Cisco Default. Supports the following modes: Normal Response Mode ? as per Secondary under SDLC; Asynchronous Response Mode allows
secondary to communicate without permission; Asynchronous Balanced mode combines the two stations. Has lower overhead than LAPB but less error checking.
Modular Switch/VIP Syntax
type slot/port (example: e 2/1)
type slot/port-adapter/port (example: e 2/0/1)
