1+1 |
A method of protecting traffic in which a protection channel exists for each working traffic channel. For optical systems, the protection channel fibers can be routed over a path separate from the working fibers. The traffic signal is bridged to both the working and protection transmitters so the protection signal can be selected quickly if the working channel fails. |
1:n |
A method of protecting traffic in which one protection channel exists for n traffic channels. Only one traffic channel can be switched to the protection channel at any given time. |
1G mobile network |
First generation mobile network. Refers to the initial category of mobile wireless networks that use analog technology only. Advanced Mobile Phone Service (AMPS) is an example of a 1G mobile network standard. |
10Base2 |
10-Mbps baseband Ethernet specification using 50-ohm thin coaxial cable. 10Base2, which is part of the IEEE 802.3 specification, has a distance limit of 606.8 feet (185 meters) per segment. See also Cheapernet, EtherChannel, IEEE 802.3, and Thinnet. |
10Base5 |
10-Mbps baseband Ethernet specification using standard (thick) 50-ohm baseband coaxial cable. 10Base5, which is part of the IEEE 802.3 baseband physical layer specification, has a distance limit of 1640 feet (500 meters) per segment. See also EtherChannel and IEEE 802.3. |
10BaseF |
10-Mbps baseband Ethernet specification that refers to the 10BaseFB, 10BaseFL, and 10BaseFP standards for Ethernet over fiber-optic cabling. See also 10BaseFB, 10BaseFL, 10BaseFP, and EtherChannel. |
10BaseFB |
10-Mbps baseband Ethernet specification using fiber-optic cabling. 10BaseFB is part of the IEEE 10BaseF specification. It is not used to connect user stations, but instead provides a synchronous signaling backbone that allows additional segments and repeaters to be connected to the network. 10BaseFB segments can be up to 1.24 miles (2000 meters) long. See also 10BaseF and EtherChannel. |
10BaseFL |
10-Mbps baseband Ethernet specification using fiber-optic cabling. 10BaseFL is part of the IEEE 10BaseF specification and, although able to interoperate with FOIRL, is designed to replace the FOIRL specification. 10BaseFL segments can be up to 3280 feet (1000 meters) long if used with FOIRL, and up to 1.24 miles (2000 meters) if 10BaseFL is used exclusively. See also 10BaseF, EtherChannel, and FOIRL. |
10BaseFP |
10-Mbps fiber-passive baseband Ethernet specification using fiber-optic cabling. 10BaseFP is part of the IEEE 10BaseF specification. It organizes a number of computers into a star topology without the use of repeaters. 10BaseFP segments can be up to 1640 feet (500 meters) long. See also 10BaseF and EtherChannel. |
10BaseT |
10-Mbps baseband Ethernet specification using two pairs of twisted-pair cabling (Categories 3, 4, or 5): one pair for transmitting data and the other for receiving data. 10BaseT, which is part of the IEEE 802.3 specification, has a distance limit of approximately 328 feet (100 meters) per segment. See also EtherChannel and IEEE 802.3. |
10Broad36 |
10-Mbps broadband Ethernet specification using broadband coaxial cable. 10Broad36, which is part of the IEEE 802.3 specification, has a distance limit of 2.24 miles (3600 meters) per segment. See also EtherChannel and IEEE 802.3. |
100BaseFX |
A 100-Mbps baseband Fast Ethernet specification using two strands of multimode fiber-optic cable per link. To guarantee proper signal timing, a 100BaseFX link cannot exceed 1312 feet (400 meters) in length. Based on the IEEE 802.3 standard. See also 100BaseX, Fast Ethernet, and IEEE 802.3. |
100BaseT |
100-Mbps baseband Fast Ethernet specification using UTP wiring. Like the 10BaseT technology on which it is based, 100BaseT sends link pulses over the network segment when no traffic is present. However, these link pulses contain more information than those used in 10BaseT. Based on the IEEE 802.3 standard. See also 10BaseT, Fast Ethernet, and IEEE 802.3. |
100BaseT4 |
100-Mbps baseband Fast Ethernet specification using four pairs of Categories 3, 4, or 5 UTP wiring. To guarantee the proper signal timing, a 100BaseT4 segment cannot exceed 328 feet (100 meters) in length. Based on the IEEE 802.3 standard. See also Fast Ethernet and IEEE 802.3. |
100BaseTX |
100-Mbps baseband Fast Ethernet specification using two pairs of either UTP or STP wiring. The first pair of wires receives data; the second transmits data. To guarantee the proper signal timing, a 100BaseTX segment cannot exceed 328 feet (100 meters) in length. Based on the IEEE 802.3 standard. See also 100BaseX, Fast Ethernet, and IEEE 802.3. |
100BaseX |
100-Mbps baseband Fast Ethernet specification that refers to the 100BaseFX and 100BaseTX standards for Fast Ethernet over fiber-optic cabling. Based on the IEEE 802.3 standard. See also 100BaseFX, 100BaseTX, Fast Ethernet, and IEEE 802.3. |
100VG-AnyLAN |
100-Mbps Fast Ethernet and Token Ring media technology using four pairs of Categories 3, 4, or 5 UTP cabling. This high-speed transport technology, developed by Hewlett-Packard, can operate on existing 10BaseT Ethernet networks. Based on the IEEE 802.12 standard. See also IEEE 802.12. |
1000Base-F |
A 1-Gbps IEEE standard for Ethernet LANs. |
2B1Q |
2 binary 1 quaternary. An encoding scheme that provides a 2 bits per baud, 80-kbaud per second, 160-kbps transfer rate. The most common signaling method on ISDN U interfaces. The 1988 ANSI spec T1.601 defines this protocol in detail. |
2G mobile network |
second generation mobile network. Refers generically to a category of mobile wireless networks and services that implement digital technology. GSM is an example of a 2G mobile network standard. |
2G+ mobile network |
second generation plus mobile network. Refers generically to a category of mobile wireless networks that support higher data rates than 2G mobile networks. GPRS is an example of a 2G+ mobile network standard. |
24th channel signaling |
See 2G mobile network. |
3G mobile network |
third generation mobile network. Refers generically to a category of next-generation mobile networks, such as UMTS and IMT-2000. |
370 block mux channel |
4B/5B local fiber |
4-byte/5-byte local fiber. Fiber channel physical media used for FDDI and ATM. Supports speeds up to 100 Mbps over multimode fiber. See also TAXI 4B/5B. |
6BONE |
The Internet's experimental IPv6 network. |
8B/10B local fiber |
8-byte/10-byte local fiber. Fiber channel physical media that supports speeds up to 149.76 Mbps over multimode fiber. |
802.x |
A set of IEEE standards for the definition of LAN protocols. |
822 |
The short form of RFC 822. Refers to the format of Internet-style e-mail as defined in RFC 822. |
1822 |
Minggu, 28 Desember 2008
Internetworking Terms and Acronyms - Numerics
Understanding Subnetting
Understanding Subnetting
Subnetting allows you to create multiple logical networks that exist within a single Class A, B, or C network. If you do not subnet, you are only able to use one network from your Class A, B, or C network, which is unrealistic.
Each data link on a network must have a unique network ID, with every node on that link being a member of the same network. If you break a major network (Class A, B, or C) into smaller subnetworks, it allows you to create a network of interconnecting subnetworks. Each data link on this network would then have a unique network/subnetwork ID. Any device, or gateway, connecting n networks/subnetworks has n distinct IP addresses, one for each network / subnetwork that it interconnects.
In order to subnet a network, extend the natural mask using some of the bits from the host ID portion of the address to create a subnetwork ID. For example, given a Class C network of 204.17.5.0 which has a natural mask of 255.255.255.0, you can create subnets in this manner:
204.17.5.0 - 11001100.00010001.00000101.00000000
255.255.255.224 - 11111111.11111111.11111111.11100000
--------------------------|sub|----
By extending the mask to be 255.255.255.224, you have taken three bits (indicated by "sub") from the original host portion of the address and used them to make subnets. With these three bits, it is possible to create eight subnets. With the remaining five host ID bits, each subnet can have up to 32 host addresses, 30 of which can actually be assigned to a device since host ids of all zeros or all ones are not allowed (it is very important to remember this). So, with this in mind, these subnets have been created.
204.17.5.0 255.255.255.224 host address range 1 to 30
204.17.5.32 255.255.255.224 host address range 33 to 62
204.17.5.64 255.255.255.224 host address range 65 to 94
204.17.5.96 255.255.255.224 host address range 97 to 126
204.17.5.128 255.255.255.224 host address range 129 to 158
204.17.5.160 255.255.255.224 host address range 161 to 190
204.17.5.192 255.255.255.224 host address range 193 to 222
204.17.5.224 255.255.255.224 host address range 225 to 254
Note: There are two ways to denote these masks. First, since you are using three bits more than the "natural" Class C mask, you can denote these addresses as having a 3-bit subnet mask. Or, secondly, the mask of 255.255.255.224 can also be denoted as /27 as there are 27 bits that are set in the mask. This second method is used with CIDR. Using this method, one of these networks can be described with the notation prefix/length. For example, 204.17.5.32/27 denotes the network 204.17.5.32 255.255.255.224. When appropriate the prefix/length notation is used to denote the mask throughout the rest of this document.
The network subnetting scheme in this section allows for eight subnets, and the network might appear as:
Notice that each of the routers in Figure 2 is attached to four subnetworks, one subnetwork is common to both routers. Also, each router has an IP address for each subnetwork to which it is attached. Each subnetwork could potentially support up to 30 host addresses.
This brings up an interesting point. The more host bits you use for a subnet mask, the more subnets you have available. However, the more subnets available, the less host addresses available per subnet. For example, a Class C network of 204.17.5.0 and a mask of 255.255.255.224 (/27) allows you to have eight subnets, each with 32 host addresses (30 of which could be assigned to devices). If you use a mask of 255.255.255.240 (/28), the break down is:
204.17.5.0 - 11001100.00010001.00000101.00000000
255.255.255.240 - 11111111.11111111.11111111.11110000
--------------------------|sub |---
Since you now have four bits to make subnets with, you only have four bits left for host addresses. So in this case you can have up to 16 subnets, each of which can have up to 16 host addresses (14 of which can be assigned to devices).
Take a look at how a Class B network might be subnetted. If you have network 172.16.0.0 ,then you know that its natural mask is 255.255.0.0 or 172.16.0.0/16. Extending the mask to anything beyond 255.255.0.0 means you are subnetting. You can quickly see that you have the ability to create a lot more subnets than with the Class C network. If you use a mask of 255.255.248.0 (/21), how many subnets and hosts per subnet does this allow for?
172.16.0.0 - 10101100.00010000.00000000.00000000
255.255.248.0 - 11111111.11111111.11111000.00000000
-----------------| sub |-----------
You are using five bits from the original host bits for subnets. This allows you to have 32 subnets (25). After using the five bits for subnetting, you are left with 11 bits for host addresses. This allows each subnet so have 2048 host addresses (211), 2046 of which could be assigned to devices.
Note: In the past, there were limitations to the use of a subnet 0 (all subnet bits are set to zero) and all ones subnet (all subnet bits set to one). Some devices would not allow the use of these subnets. Cisco Systems devices allow the use of these subnets when theip subnet zero
command is configured.
Sabtu, 27 Desember 2008
Network Masks
Network Masks
A network mask helps you know which portion of the address identifies the network and which portion of the address identifies the node. Class A, B, and C networks have default masks, also known as natural masks, as shown here:
Class A: 255.0.0.0
Class B: 255.255.0.0
Class C: 255.255.255.0
An IP address on a Class A network that has not been subnetted would have an address/mask pair similar to: 8.20.15.1 255.0.0.0. To see how the mask helps you identify the network and node parts of the address, convert the address and mask to binary numbers.
8.20.15.1 = 00001000.00010100.00001111.00000001
255.0.0.0 = 11111111.00000000.00000000.00000000
Once you have the address and the mask represented in binary, then identifying the network and host ID is easier. Any address bits which have corresponding mask bits set to 1 represent the network ID. Any address bits that have corresponding mask bits set to 0 represent the node ID.
8.20.15.1 = 00001000.00010100.00001111.00000001
255.0.0.0 = 11111111.00000000.00000000.00000000
-----------------------------------
net id | host id
netid = 00001000 = 8
hostid = 00010100.00001111.00000001 = 20.15.1
Jumat, 26 Desember 2008
Understanding IP Addresses
Understanding IP Addresses
An IP address is an address used to uniquely identify a device on an IP network. The address is made up of 32 binary bits which can be divisible into a network portion and host portion with the help of a subnet mask. The 32 binary bits are broken into four octets (1 octet = 8 bits). Each octet is converted to decimal and separated by a period (dot). For this reason, an IP address is said to be expressed in dotted decimal format (for example, 172.16.81.100). The value in each octet ranges from 0 to 255 decimal, or 00000000 - 11111111 binary.
Here is how binary octets convert to decimal: The right most bit, or least significant bit, of an octet holds a value of 20. The bit just to the left of that holds a value of 21. This continues until the left-most bit, or most significant bit, which holds a value of 27. So if all binary bits are a one, the decimal equivalent would be 255 as shown here:
1 1 1 1 1 1 1 1
128 64 32 16 8 4 2 1 (128+64+32+16+8+4+2+1=255)
Here is a sample octet conversion when not all of the bits are set to 1.
0 1 0 0 0 0 0 1
0 64 0 0 0 0 0 1 (0+64+0+0+0+0+0+1=65)
And this is sample shows an IP address represented in both binary and decimal.
10. 1. 23. 19 (decimal)
00001010.00000001.00010111.00010011 (binary)
These octets are broken down to provide an addressing scheme that can accommodate large and small networks. There are five different classes of networks, A to E. This document focuses on addressing classes A to C, since classes D and E are reserved and discussion of them is beyond the scope of this document.
Note: Also note that the terms "Class A, Class B" and so on are used in this document to help facilitate the understanding of IP addressing and subnetting. These terms are rarely used in the industry anymore because of the introduction of classless interdomain routing (CIDR).
Given an IP address, its class can be determined from the three high-order bits. Figure 1 shows the significance in the three high order bits and the range of addresses that fall into each class. For informational purposes, Class D and Class E addresses are also shown.
In a Class A address, the first octet is the network portion, so the Class A example in Figure 1 has a major network address of 1.0.0.0 - 127.255.255.255. Octets 2, 3, and 4 (the next 24 bits) are for the network manager to divide into subnets and hosts as he/she sees fit. Class A addresses are used for networks that have more than 65,536 hosts (actually, up to 16777214 hosts!).
In a Class B address, the first two octets are the network portion, so the Class B example in Figure 1 has a major network address of 128.0.0.0 - 191.255.255.255. Octets 3 and 4 (16 bits) are for local subnets and hosts. Class B addresses are used for networks that have between 256 and 65534 hosts.
In a Class C address, the first three octets are the network portion. The Class C example in Figure 1 has a major network address of 192.0.0.0 - 233.255.255.255. Octet 4 (8 bits) is for local subnets and hosts - perfect for networks with less than 254 hosts.
Kamis, 25 Desember 2008
SNMP Router Monitor
The benefits of using ByteOMeter with an SNMP router
A common setup in a broadband connected home consists of one or more computers and game consoles, a DSL or cable modem and a router. The router acts as a middleman between your equipment and the internet. While providing a firewall against hackers and other unwanted visitors, it also takes care of directing all the traffic flowing from your network to the internet and the other way around.
Track all traffic by monitoring an SNMP router
If there is more than one network device connected to the router, it is difficult to accurately track how much bandwidth is being used at any given time and how much data in total has been transferred on the connection. A normal bandwidth monitoring program typically monitors only the network cards in the computer on which it is installed. Therefore, it cannot detect a filetransfer being made on another computer or the traffic generated by a game console being used for online play. However, if the router, through which all the traffic flows, is SNMP enabled it can provide various information about itself, including traffic totals.
SNMP (Simple Network Management Protocol) is a network protocol which ByteOMeter speaks as of version 1.5. This means that ByteOMeter can monitor SNMP enabled routers and therefore provides the following benefits over other bandwidth monitors:
- Internet traffic from the whole network is monitored.
- ByteOMeter does not need to be running all the time to log traffic*.
- Internet traffic is distinguished from local network traffic.
- Traffic generated by other PCs or even game consoles shows up in the real-time graph window.
In order to gain these advantages, your router must be SNMP enabled. An easy way to check this is to simply download ByteOMeter and enter the router setup - if it is there ByteOMeter is ready to monitor the SNMP router right away..
*ByteOMeter must sometimes be turned on to obtain information from the router in order to eg. provide a warning if traffic limits are exceeded.
Download ByteOMeter
Try the 30 day evalutation of ByteOMeter:
The trial version of ByteOMeter is fully functional for 30 days. If you wish to continue using ByteOMeter after this period you can register to obtain full functionality and get free updates in the future.
Please note that Windows Vista is NOT currently supported.
Minimal System Requirements:
Windows 2000/XP/2003 Server
Pentium II CPU
32 MB RAM
5 MB harddisk space
Rabu, 24 Desember 2008
CCNA 2 Exploration - Module 11
CCNA 2 Exploration - Module 11
Refer to the exhibit. What does the "O*E2" from the "O*E2 0.0.0.0/0 [110/1] via 192.168.1.1, 00:05:34, Serial0/0" line represent?
an external OSPF route that will not increment in cost.
Refer to the exhibit. What is the cost of the route to the 10.0.0.0 network?
1786
What three parameters must be indentical between OSPF routers in order to form an adjacency? (Choose three.)
area id
hello interval
network type
What does OSPF use to reduce the number of exchanges of routing information in networks where large numbers of neighbors are present? (Choose two.)
designated router
backup designated router
What does OSPF use to calculate the cost to a destination network?
bandwidth
A fully converged five router OSPF network has been running successfully for several weeks. All configurations have been saved and no static routes are used. If one router looses power and reboots, what information will be in its routing table after the configuration file is loaded but before OSPF has converged?
Routes for connected networks that are operational will be in the routing table.
Refer to the exhibit. Router A is correctly configured for OSPF. Which OSPF configuration statement or set of statements was entered for router B to generate the exhibited routing table?
B(config-router)# network 192.168.1.0 0.0.0.3 area 0
Refer to the exhibit. Which network command or set of sommands will cause OSPF to be enabled to send and receive packets for any R1 interface in the exhibited subnets?
R1(config-router)# network 0.0.0.0 255.255.255.255 area 0
Refer to the exhibit. What does the "2" stand for in the router ospf 2 statement?
The number 2 identifies this particular instance of OSPF on this router.
Refer to the exhibit. All routers have been configured with the interface priorities that are shown. All routers were restarted simultaneously. The results of the DR/BDR election are shown. What can be concluded about this network?
The highest router ID was most likely determined via an OSPF router-id statement or statements.
Refer to the exhibit. What configuration statements would give the results that are shown in the output of the show ip protocols command?
B(config)# router ospf 1
B(config-router)# router-id 192.168.1.5
Refer to the exhibit. How many OSPF adjacencies must be formed to build the complete topology if a DR or BDR were not elected in this OSPF network?
6
What is the default administrative distance for OSPF?
110
Refer to the exhibit. Routers A, B, C, and D are all running OSPF with default router IDs and OSPF interface priorities. Loopback interfaces are not configured and all interfaces are operational. Router D is the DR and router C is the BDR.
What happens immediately after the following commands are entered on router A?
A(config)# interface fa0/0
A(config-if)# ip ospf priority 255
D will remain the DR. C will remain the BDR.
Refer to the exhibit. All routers are running OSPF. What cost would JAX put in its routing table for the 10.0.0.0/24 network?
1787
What range of networks will be advertised in the OSPF updates by the command Router1(config-router)# network 192.168.0.0 0.0.15.255 area 100?
192.168.0.0/24 through 192.168.15.0/24
Refer to the exhibit. The network administrator wants to set the router ID of Router1 to 192.168.100.1. What steps must the administrator take to accomplish this?
nothing, the router-id of Router1 is already 192.168.100.1
Refer to the exhibit. When OSPF is operational in the exhibited network, what neighbor relationship is developed between Router1 and Router2?
A FULL adjacency is formed.
Refer to the exhibit. Assuming that the routers have default interface OSPF priorities and no configured loopback interfaces, what two roles will router B play on each network segment? (Choose two.)
DR for network 192.168.1.200
BDR for network 192.168.1.204
Refer to the exhibit. Router1 and Router2 are running OSPF. The show ip ospf neighbor command reveals no neighbors. What is a possible cause?
OSPF hello or dead timers do not match.
Refer to the exhibit. Which command sequence on RouterB will redistribute a gateway of last resort to the other routers in OSPF area 0?
RouterB(config)# ip route 0.0.0.0 0.0.0.0 172.16.6.6
RouterB(config)# router ospf 10
RouterB(config-router)# default-information originate
Refer to the exhibit. RouterA, RouterB, and RouterC in the diagram are running OSPF on their Ethernet interfaces. Router D was just added to the network. Routers are configured with the loopback interfaces (Lo 0) that are shown in the exhibit. What happens to the OSPF DR/BDR after RouterD is added to the network?
There is no change in the DR or BDR until either current DR or BDR goes down.
Which two statements describe the use of OSPF DR/BDR elections? (Choose two.)
Elections are required in broadcast multiaccess networks.
Elections are required in non-broadcast multiaccess networks.
Refer to the exhibit. The routers in the exhibit are using default OSPF configuration settings to advertise all attached networks. If all of the routers start at the same time, what will be the result of the DR and BDR elections for this single area OSPF network? (Choose three.)
Router A will be DR for 10.4.0.0/16.
HQ will be BDR for 10.4.0.0/16.
Remote will be DR for 10.5.0.0/16.
Refer to the exhibit. What must be received between neighbors to prevent the dead time that is shown in the exhibit from reaching zero?
hello packets
CCNA 2 Exploration - Module 10
CCNA 2 Exploration - Module 10
Refer to the exhibit. When Router D is configured to use a link-state routing protocol and is added to the network, what is the first thing that it does to begin learning the network topology?
It learns about its directly connected networks when its interfaces reach the up state.
What two events will cause a link state router to send LSPs to all neighbors? (Choose two.)
whenever the network topology changes
upon initial startup of router or routing protocol
What is the final step in the link state routing process?
SPF computes best path to each destination network
What two statements correctly describe the link state routing process? (Choose two.)
each router in the area floods LSPs to all neighbors
all routers in the area have identical link state databases
Refer to the exhibit. What kind of information would be seen in an LSP sent from router JAX to router ATL?
cost of the link
What feature do modern link-state protocols provide to minimize processing and memory requirements?
splitting routing topologies into smaller areas
To achieve network convergence, what three steps does each link state router take? (Choose three.)
build a Link State Packet (LSP) containing the state of each directly connected link
flood the LSP to all neighbors, who then store all LSPs received in a database
construct a complete map of the topology and compute the best path to each destination network
What speeds up convergence in a network using link-state routing?
updates triggered by network changes
Why is it difficult for routing loops to occur in networks that use link-state routing?
Each router builds a complete and synchronized view of the network.
What are some of the advantages of using a link-state routing protocol instead of a distance vector routing protocol? (Choose two.)
Routers have direct knowledge of all links in the network and how they are connected.
After the inital LSA flooding, they generally require less bandwidth to communicate changes in a topology.
Which algorithm is run by link-state routing protocols to calculate the shortest path to destination networks?
Dijkstra
Refer to the exhibit. Which statement correctly describes the path traffic would take from the 10.0.0.0/24 network to the 192.168.1.0/24 network if a link-state routing protocol was in use?
BOS -> ORL -> JAX -> ATL because this path is the lowest cost
Which database or table must be identical on all link-state routers within an area in order to construct an accurate SPF tree?
link-state database
Which two routing protocols use Dijkstra’s shortest path first algorithm? (Choose two.)
IS-IS
OSPF
When are link-state packets sent to neighbors?
when a link goes up or down
Refer to the exhibit. What does JAX do with link-state packets from ORL?
sends out the individual link-state packets out the interface connected to BOS
A new network administrator is given the task of selecting an appropriate dynamic routing protocol for a software development company. The company has over 100 routers, uses CIDR and VLSM, requires fast convergence, and uses both Cisco and non-Cisco equipment. Which routing protocol is appropriate for this company?
OSPF
What action does a link-state router take immediately upon receipt of an LSP from a neighboring router?
floods the LSP to neighbors
Refer to the exhibit. If all routers and interfaces are configured to use a link-state routing protocol, from which routers will router D receive hello packets?
B and C
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