These notes are for myself. Some are sort of cryptic. They may or may not help you out. They are for the Cisco Certified Network Associate exam.
Binary bits (big endian): 128 64 32 16 8 4 2 1
example: 1 0 0 0 0 0 0 1 = 129
* Wildcard (reversed!)
00000000 = 0 0 255 00000000 = 0
10000000 = 128 0 128 00000001 = 1
11000000 = 192 2 64 00000011 = 3
11100000 = 224 6 32 00000111 = 7
11110000 = 240 14 16 00001111 = 15
11111000 = 248 30 8 00011111 = 31
11111100 = 252 62 4 00111111 = 63
11111110 = 254 126 2 01111111 = 127
11111111 = 255 254 0 11111111 = 255
* Routers can enable subnet zero to increase the host
count by 1 (WARNING,
old BSD based UNIX systems use subnet 0 for broadcast! If you have old BSD
systems on your network, do not enable subnet 0)
CIDR addressing (RFC 1519, Introduction date: 1993)
The new (generally accepted around 1997 I guess) way of showing network
address ranges is CIDR addressing (Classless Inter-Domain Routing) which
is written as a slash and a number, i.e. "/24". The slash number represents
how many bits are in the netmask. Thus, a /24 is 24 bits which is a
"classic" Class C address space (the bits go from left to right [big endian]).
mask: 255 . 255 . 255 . 0
range: x.x.x.0 - x.x.x.255 (remember, everything is octal so 2^8 - 1 is 255)
example: 10.0.0.0 - 10.0.0.255 (A "classic" Class C address space)
There are alot of weird address allocations now that CIDR is being
used (the old Class networks are no longer used for the most part).
For instance, a company may have a /23 address space which is:
mask: 255 . 255 . 254 . 0
range: x.x.x.0 - x.x.1.255
example: 10.0.0.0 - 10.0.1.255 (assuming the first subnet of /23)
A Class A network (/8, 255.0.0.0) can have 2^24 - 2 = 16,777,214
A Class B network (/16, 255.255.0.0) can have 2^16 - 2 = 65,534 hosts
A Class C network (/24, 255.255.255.0) can have 2^8 - 2 = 253 hosts
It's amazing how much address space is wasted. I once consulted
company that had a full Class A allocation, but only had around 80,000
computers in the entire company. (They were also really stupid and put
live addresses on each desktop instead of using private address space
Calculations: 256 - netmask = subnetwork
example: 256 - 240 = 16 so subnetworks are: 0, 16, 32, 48, etc.
broadcast are: 15, 31, 47, etc.
host ranges are: 1-14, 17-30, 33-46, etc.
Number of subnets: 2^x - 2 where x = number of mask bits
example: mask of 192 is 2 bits, 2^2 - 2 = 2 subnets
Number of hosts: 2^x - 2 where x = number of unmasked bits
example: mask of 192 is 6 unmasked bits 2^6 - 2 = 62
0 Directly connected
0 Static route pointing to an interface
1 Static route pointing to a next-hop neighbor
5 Summarized EIGRP route
20 External BGP route
90 Internel EIGRP route
100 IGRP route
110 OSPF route
115 IS-IS route
120 RIP route
140 EGP route
170 External EIGRP route
200 Internal BGP route
255 Unknown routing source
Two types of links in a switched environment: Access and Trunk links.
- Access links: Links that are only part of one VLAN. VLAN information is removed from frame before it goes out the port.
- Trunk links: Trunks carry multiple VLANs. Used to connect to other switches, routers, or servers.
- Two types of Trunk framing: ISL (Cisco only) and 802.1.q
- Can carry 1 to 1005 VLANs
- Frame tagging: assignes user-defined ID to each frame, sometimes called a VLAN ID.
- Frame types: Inter-Switch Link (ISL) Fast Ethernet and GigaEthernet only. Cisco Only
- Adds a 26 byte header and a 4 byte FCS, can create a GIANT packet (1522 bytes)
IEEE 802.1.q IEEE standard
LAN emulation (LANE) used with ATM
802.10 used with FDDI
- VLAN Trunk Protocol (VTP)
Server, client, and transparent server
Advertisements are sent every 5 minutes or whenever there is a change
VTP pruning: Updates are onyl sent to devices on the VLAN that changed. Off by default.
r2509#sh cdp nei
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater
Local Intrfce Holdtme Capability
Platform Port ID
r2514 Eth 0 162 R 2500 Eth 0
r2504 Ser 1 175 R 2500 Ser 0
r2501 Eth 0 178 R 2500 Eth 0
r2509#sh cdp nei detail
Device ID: r2514
IP address: 10.0.0.14
Platform: cisco 2500, Capabilities: Router
Interface: Ethernet0, Port ID (outgoing port): Ethernet0
Holdtime : 124 sec
Cisco Internetwork Operating System Software
IOS (tm) 2500 Software (C2500-JS-L), Version 11.2(17), RELEASE SOFTWARE (fc1)
Copyright (c) 1986-1999 by cisco Systems, Inc.
Compiled Mon 04-Jan-99 17:27 by ashah
Device ID: r2504
IP address: 172.16.1.2
Platform: cisco 2500, Capabilities: Router
Interface: Serial1, Port ID (outgoing port): Serial0
Ethernet_802.3 up to NW 3.11
Ethernet_802.2 since NW 3.12
Ethernet_II supports both TCP/IP and IPX
Ethernet_SNAP Appletalk, IPX, and TCP/IP
Novell frame type Cisco Keyword
--------- ----------------- --------------
Ethernet Ethernet_802.3 novell-ether (default)
Token Ring Token-Ring sap (default)
FDDI Fddi_snap snap (default)
IPX routing is easy:
r2509(config-if)#ipx network 10
r2509(config-if)#ipx network 10a
r2509#sh ipx route
Codes: C - Connected primary network, c - Connected secondary network
S - Static, F - Floating static, L - Local (internal), W - IPXWAN
R - RIP, E - EIGRP, N - NLSP, X - External, A - Aggregate
s - seconds, u - uses
2 Total IPX routes. Up to 1 parallel paths and 16 hops allowed.
No default route known.
10 (NOVELL-ETHER), Et0
C 10A (HDLC), Se1
Note: "the 1 parallel paths".
To enable load balancing, enter
r2509(config)#ipx maximum-paths 2
To enable load balancing on a per host basis, enter:
r2509#sh ipx ?
access-lists IPX access lists
accounting The active IPX accounting database
cache IPX fast-switching cache
compression IPX compression information
eigrp IPX EIGRP show commands
interface IPX interface status and configuration
nasi Netware Asynchronous Services Interface status
nhrp NHRP information
nlsp Show NLSP information
route IPX routing table
servers SAP servers
spx-protocol Sequenced Packet Exchange protocol status
spx-spoof SPX Spoofing table
traffic IPX protocol statistics
IP extended can be based on IP proto, eigrp, gre, icmp, igmp, igrp,
ip, ipinip, nos, ospf, tcp, udp, ahp, esp
LMI Local Mangement Interface. Types: cisco, ansi, q933a
NOTE: A U interface has a built in NT1, A S/T interface does not. (some Sun computers have a built in S/T. Also, SGI Indy's have a S/T.)
North America uses U interface (2 wire). Needs NT1
to convert to 4 wire S/T
TE1 Terminal Equipment type 1. Can plug right into ISDN network
TE2 Terminal Equipment type 2. Older equipment, needs TA
NT1 Network Termination 1 implements the ISDN physical layer for user
NT2 Network Termination 2 is the provider's equipment, PBX, etc
TA Terminal Adapter converts TE2 to TE1 wiring.
R reference point. Defines point between non-ISDN equipment
(TE2) and TA.
S reference point. Defines point between customer's router and a NT2
T reference point. Defines point between NT1 and NT2. S and T can be the same.
U reference point. Defines point between NT1 and line-termination equipment (NT2) (No TA/NT1 needed).
ITU Protocols: protocols beginning with:
E deal with ISDN on existing network (POTS)
I deal with concepts, aspects, services
Q deal with switching and signaling
isdn q921 layer 2
isdn q931 layer 3
Copyright © 1993-2001 by Robert Barnes