The last certification is the CCIE, and is the most promising certification in the market. Besides its difficulty it challenges those with specific troubleshooting methods and configuration techniques. Covering a wide variety of technologies and protocols. The CCIE is composed of a qualification written test and of course a two day lab exam which makes the CCIE what it is today.
　　
　　
　　1.Erlang B.
　　
　　Erlang B ia an algorithm used to handles trunk allocation.
　　In the circuit switch environment, many of the larger switches were blocking other switches. That is, not every input had a path to every output. Complex grading structures were created to help determine the pathways a circuit might take through the switch, and the impact on the GoS.
　　
　　It should be recognized that traffic theory consists of many queuing methods and associated formulas. Anyone who has taken a queuing theory class can testify to the degree of complexity of the many queuing models that have been derived for various situations.
　　
　　The most commonly used model and table is Erlang B. Erlang B is based on infinite sources, LCC, and Poisson distribution that is appropriate for either exponential or constant holding times. In general, Erlang B understates the number of trunks because of the LCC assumption, but it is generally the most commonly used algorithm.
　　
　　
　　2.Counting To Infinity
　　
　　A distance vector routing protocol uses infinity to know when a route is really down. Counting to infinity is good (and necessary for these protocols to work).
　　If the hop count rises to a certain number, it is considered unreachable and removed from the routing table and not propagated further. In RIP v1, the infinity hop count was only 16. This led to quick convergence but a small network diameter.
　　
　　Count to infinity helps keep false routes from propagating for non adjacent routers while split-horizon does the same for adjacent routers.
　　
　　
　　3.Multicast Layers
　　
　　IP Multicast lies at Layers 2 and 3 on the OSI layer model
　　
　　
　　4.X.25 Maximum Speed
　　
　　The Maximum Speed for X.25 is 2MB/s
　　
　　
　　5.DS-1
　　
　　A DS-1 circuit consist of 24 byte interleaved 8 Bit and 1 framing bit
　　
　　
　　6.IPX Split Horizon
　　
　　IPX Split Horizon is not supported in any of the IPX feature sets.
　　
　　
　　7.Default Maximum Servers for SAP
　　SAP updates sends out a maximum default of 7 services
　　
　　
　　8.Spanning Tree and Root Bridge
　　1 Root Bridge for Ethernet and switching, also 1 root bridge per vlan with 1 for all vlans.
　　
　　
　　9.Route Dampening Policy
　　Route dampening is a BGP feature designed to minimize the propagation of flapping routes across an internetwork. A route is considered to be flapping when it is repeatedly available, then unavailable, then available, then unavailable, and so on.
　　A route that is flapping receives a penalty of 1000 for each flap. When the accumulated penalty reaches a configurable limit, BGP suppresses advertisement of the route even if the route is up. The accumulated penalty is decremented by the half-life time. When the accumulated penalty is less than the reuse limit, the route is advertised again (if it is still up).
　　
　　
　　10.BGP Route Reflector
　　
　　A route reflector reflects routes for other IBGP router ie it receive data and distribute it to all other routers
　　BGP Confederations
　　
　　Confederations eliminated the need to fully meshed BGP communication. Basically splitting a single AS into confederations allows the same AS to speak EBGP, although to all external AS the entire confederation grouping looks like a single AS.
　　
　　
　　11.FDDI 4B/5B
　　4B/5B local fiber.
　　It is the Fiber channel physical media used for FDDI and ATM.Supports speeds of up 100Mbps over multimode fiber.(see note about TAXI 4B/5B)
　　TAXI 4B/5B
　　It is a Transmitter/receiver Interface 4-byte/5-Byte. Encoding sheme used for FDDI LANs, as well as for ATM. Supports speeds of up 100Mbps over multimode fiber.TAXI is the chipset that generates 4B/5B encoding on multimode fiber.
　　
　　Five bit encoding provides 16 data symbols (0-F), 8 control symbols (Q, H, I, J, K, T, R, S), and 8 violation symbols (V). The coding of these symbols is done such that in normal situations, you will not ever have 4 consecutive zeros in a row. "
　　
　　
　　12.TCP PSH/RST
　　TCP RST
　　When TCP session sequence numbers are received out of sequence the detecting station will send a reset. This forces the session to abort.
　　TCP PSH/RST
　　If you look at the TCP header format. There is a six bit field called FLAGS. FLAGS are used for data flow and connection control. Valid flags are URG (urgent) ACK (acknowledgement) PSH (push) RST (reset) SYN (syncronize) and FIN (final) they are viewable with a decent sniffer trace of a TCP session.
　　
　　13.CIDR
　　Classless Interdomain Routing, CIDR used by BGP ver 4.
　　
　　
　　14.IPX Load Balancing
　　IPX supports load balancing, but it is not on automatically. You must manually issue the global command : IPX maximum-path 2(I just picked 2 because I assumed there are only two parallel paths).
　　
　　
　　15.Fast Link Pulse (FLP)
　　100 base t auto-negotation link pulse.
　　
　　
　　16.Realiable Protocols
　　TCP and LLC Type 2 are realiable protocols while protocols such as IP, UDP, and Frame Relay are NOT realiable protocols.
　　
　　
　　17.802.10 VLAN Encapsulation
　　802.10 VLAN encapsulation media type is FDDI.
　　
　　
　　18.802.2 Standard
　　The information for IEEE 802.2 standard is the LLC or Link Layer Control
　　
　　
　　19.DecNet Designated Router Configuration
　　To setup a specific router to the designated router, the command syntz would be the following:
　　decnet router-priority xxx (higher the number for choosing the DR)
　　(i.e. decent router-priority 76)
　　
　　
　　20.If a person lost there password or just forgot the password, then do the following?
　　Break into the router and change the router or replace the password. Do not write erase, cause that won't do anything but making you start all over again. You also do not need to copy the nothing over from a TFTP server. Just break into the router, change the register value then reload the router with the new settings. Then you can go into the config and change the password.
　　
　　
　　21.Difference between Ethernet II and 802.3
　　802.3 represents a LENGTH field, while the Ethernet II represents the TYPE field.
　　
　　
　　22.When you see the following line in the config "line vty 0 4, no password", what does that mean?
　　This means that no one has direct telnet access into the router.
　　
　　
　　23.Enabling SNMP on router?
　　use the following command, "snmp-server community"
　　
　　
　　24.Administrative Distance
　　The Administrative Distance gives complete priority when choosing routes between different routing protocols like RIP or EIGRP. Here is a list of the administrative distances:
　　STATIC 1
　　EIGRP 90
　　IGRP 100
　　OSPF 110
　　ISIS 115
　　RIP 120
　　
　　25.Routing Protocols Related To IP
　　Static Routes, OSPF, ISIS, EIGRP, RIP, IGRP
　　
　　
　　26.What a SAP service does when it doesn't have a route?
　　SAP entries are dependent on routing table entries. If an entry in the routing table that SAP is referencing is removed, the SAP entries is also remove from the SAP table. When it receives an entry with no