IT Certification & Interview Help.

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CCNA INTERVIEW QUESTIONS PART-3
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What is EGP (Exterior Gateway Protocol)?
It is the protocol the routers in neighboring autonomous systems use to identify the set of networks that can be reached within or via each autonomous system.

What is Autonomous System?
A group of Networks under mutual administration that share the same routing methodology. Autonomous Systems are subdivided by Areas and must be assigned an individual 16-bit number by the IANA.

What is BGP (Border Gateway Protocol)?
It is a protocol used to advertise the set of networks that can be reached within an autonomous system. BGP enables this information to be shared with the autonomous system. This is newer than EGP (Exterior Gateway Protocol).

What is Gateway-to-Gateway protocol?
It is a protocol formerly used to exchange routing information between Internet core routers.

What is Kerberos?
An authentication mechanism used to verify user or host identity. Kerberos uses encryption to prevent intruders from discovering passwords and gaining unauthorized access to files.

What is OSPF (Open Shortest Path First)?
OSPF is the first Open Standard Link State Routing Protocol.
It’s a Classless Routing Protocol meaning when updates are sent they send both IP address and Subnet mask.
Administrative Distance is 110.
Metric used is Cost i.e. Cost= 108
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Bandwidth
OSPF uses algorithm to build Routing Table called Dijisktra.
Sends only Incremental and Triggered updates. Route updates sent within the routers will be secured with the help of MD5 encrypted password.
Routing updates are sent as Multicast addresses i.e.
224.0.0.5 – SPF (all OSPF routers)
224.0.0.6 – Designated router and Backup Designated router
OSPF maintains 3 types of Routing table i.e. Routing Table (Dijisktra), Topology Table (SPF) and Neighborship Table.
In OSPF Routers can be connected in two methods i.e.
Point-to-Point Link
Point to Multipoint Link
In OSPF a single large Autonomous system is break into small areas. There should be atleast one area by name Area 0. It’s called as Backbone Area.
The Router that connects more than one Area is called as Area Border Routers.
The Router that connects to other Autonomous system is called as Autonomous System Boundary Router.

Router ID
If the priority is set 1 to all the routers then there is a tie in priority, in this case it will check if there is any loopback address is given to any router if not the router with highest value of IP address will be elected as Router ID.
This router will be then called as Designated Router and the router with less value of IP address after Designated Router will be called as Backup Designated Router.
If a Router has all interfaces existing in single area than that router is called as Internal Router.
Whenever a router send routing updates to DR and BDR it uses Destination address as 224.0.0.6 and when DR send updates to all the routers it uses Destination address as 224.0.0.5.
In OSPF routing updates are called as Link State Advertisements.
If an OSPF router wants to send updates to other OSPF router then it should carry 3 requirements i.e.
Hello Packets Received
It contains Area Id, Uptime, Password, Hello Interval, Dead Interval, Neighborship Table and Router Id.
Point-to-Point Link Point to Multipoint Link
Halo Interval – 10 Halo Interval – 30
Dead Interval – 40 Dead Interval – 120

Adjacency Built
If both router interfaces belongs to same Area, same Password then Hallo and Dead Intervals should be set same.

Neighborship Built
If both routers are adjacent to each other then Neighborship is built in Routers.
When one routerRA sends updates i.e. Link State Advertisements to other routerRB it will send that update to Topology Database of routerRB and will run an algorithm SPF on routerRB to create a new Topology Table. After that Dijisktra Algorithm is run to find the best path and that entry will be put in Routing Table.
The router when sends Hallo packets to other router a Neighborship Table is set on that Router.


What is SLIP (Serial Line Internet Protocol)?
An industry standard serial encapsulation for point-to-point connections that supports only a single routed protocol, TCP/IP.



What is RIP (Routing Information Protocol)?
Rip run on any Routers hence called as Open Standard Distance Vector Routing Protocol.
It’s a classful routing protocol meaning when updates are sent they send only IP address but not subnet mask.
Administrative Distance is 120.
Metric used is Hop counts (number of routers to cross to reach the destination).
Rip uses algorithm name Bellman Ford Algorithm to determine the best path selection.
Supports maximum 15 Hops.
Supports 6 paths if there is a tie in metric i.e. same metric.

RIP Timers
Route update timer – 30seconds
Route invalid timer – 180 seconds
Holddown timer – 180 seconds
Route flush timer – 240 seconds

What are the advantages and disadvantages of the three types of routing tables?



What is the HELLO protocol used for?
The HELLO protocol uses time instead of distance to determine optimal routing. It is an alternative to the Routing Information Protocol.

What is the difference between interior and exterior neighbor gateways?
Interior gateways connect LANs of one organization, whereas exterior gateways connect the organization to the outside world.

What protocol do DNS name servers use?
DNS uses UDP for communication between servers. It offers a connectionless datagram service that guarantees neither delivery nor correct sequencing of delivered packets (much like IP).

What is a DNS resource record?
A resource record is an entry in a name server's database. There are several types of resource records used, including name-to-address resolution information. Resource records are maintained as ASCII files.

BOOTP helps a diskless workstation boot. How does it get a message to the network looking for its ip address?
A protocol used primarily on TCP/IP networks to configure diskless workstations. BOOTP sends a UDP message with a subnetwork broadcast address and waits for a reply from a server that gives it the IP address.