Chapter_5

Question 1

what is NAT?

Answer 1

private ipv4 addresses are used inside a network and then the border router that connects to the ISP has NAT on it. the private address is linked to and converted to a public address so that it can communicate with devices outside the local network and on the web/.

Question 2

inside address?

Answer 2

he address of the device which is being translated by NAT.

Question 3

Outside address

Answer 3

The address of the destination device.

Question 4

Local address

Answer 4

A local address is any address that appears on the inside portion of the network.

Question 5

Global address

Answer 5

A global address is any address that appears on the outside portion of the network.

Question 6

Static address translation (static NAT)

Answer 6

One-to-one address mapping between local and global addresses.

Question 7

Dynamic address translation (dynamic NAT)

Answer 7

• Many-to-many address mapping between local and global addresses.

Question 8

Port Address Translation (PAT)

Answer 8

• Many-to-one address mapping between local and global addresses. This method is also known as overloading (NAT overloading)

Question 9

what kinds of security features if any do PAT provide?

Answer 9

the router configured with PAT port address translation makes sure that the incoming packets were requested before accepting them. this is done by tracking the source ports used and assigned to each device communicating outside the network.

Question 10

difference between NAT and PAT?

Answer 10

Network Address Translation: the internal private ipv4 addresses are translated directly to one ipv4 inside global address (can come from a pool of addresses)
**PAT: Port Address Translation: the inside global address(es) can be shared by inside ipv4 private addresses because each sending host is given a sending port number that is translated by the edge router.

Question 11

how does PAT work with ICMPv4 since it is a layer 4 protocol that can be used instead of the TCP/UDP layer 4 protocol stack?

Answer 11

the ICMPv4 uses Query ID’s to identify echo requests and replies and PAT uses this ID instead of a lyer 4 port number.

Question 12

disadvantages of NAT?

Answer 12

Voip can have problems since additional switching cpu usage for each packet is needed. (real time protocol have issues)

• the tcp/UDP checksum must be recalculated each time a change is made to a packet.
• ip traceability is lost

Question 13

what is the inside local address in a nat network?

Answer 13

the address of the host devices (private ipv4)

Question 14

what is the inside global address

Answer 14

the address that is public ipv4 and is seen by outside devices on the web when trying to communicate with a host inside a network. the ipv4 NAT router converts the address.

Question 15

what is the outside local address?

Answer 15

the destination address of the server on the web

Question 16

what is the outside global address?

Answer 16

the destination address of the server/ device on the web. often same as the outside local address

Question 17

Static address translation (static NAT)?

Answer 17

One-to-one address mapping between local and global addresses.

Question 18

Dynamic address translation (dynamic NAT) ?

Answer 18

• Many-to-many address mapping between local and global addresses.

Question 19

Port Address Translation (PAT) - ?

Answer 19

Many-to-one address mapping between local and global addresses. This method is also known as overloading (NAT overloading).

Question 20

describe port forwarding and what is another name for this?

Answer 20

Tunneling: sending traffic from a specific port outside the network to a specific port inside the network. need nat router. (p2p sharing, etc.) allows access to servers from anywhere on the web.

Question 21

if one needs to get to a specific port while using a web application how is this done?

Answer 21

www.the webaddress.com:colin,port_number

Question 22

how does NAT work for ipv6?

Answer 22

ipv6 does not need NAT but instead has its own private address space built into the ipv6 address. the private space is called the ULA: unique local address and is the 1st portion of an ipv6 address.

Question 23

what is the ULA?

Answer 23

Unique Local Address: the 1st portion of an ipv6 address. for use on a local (internal) site. it is the 1st 64 bits of an ipv6 address and is not rout able by itself outside a local network.

Question 24

what is dual stack?

Answer 24

when a router/network uses both ipv4 and ipv6 routing

Question 25

what is tunneling?

Answer 25

encapsulating ipv6 inside ipv4 packets on an ipv4 only network where ipv6 routing is not available.

Question 26

when troubleshooting NAT and u see the * after NAT what does it mean
?

Answer 26

the translation is occuring in the fast switched path (fast switched memory is memory that has the packet and sender interface info saved from an earlier routing so a cpu process is not needed)

Question 27

what is NAT for ipv6?

Answer 27

temporary mechanism to assist in going from ipv4 to ipv6