RK 2021-22; LDN2¶
Ukaz arp -a¶
Ukaz arp -a nam:
What does the arp -a system command do?
| Vrstica | Odgovor |
|---|---|
| pokaže privzeti prehod. | ❌ ne drzi |
| ustvari statični zapis v tabeli ARP. | ❌ ne drzi |
| pobriše tabelo ARP. | ❌ ne drzi |
| izpiše tabelo ARP. | ✅ drzi |
SSID¶
Naslov brezžičnega omrežja SSID je:
The SSID of a wireless newtork is:
| Vrstica | Odgovor |
|---|---|
| varnostni mehanizem. | ❌ ne drzi |
| strojni (MAC) naslov. | ❌ ne drzi |
| prejemnikov naslov. | ❌ ne drzi |
| ime omrežja, ki si ga izmislimo, npr. linksys. | ✅ drzi |
Protokol za dostop do 802.11a/b/g¶
Kateri od naštetih protokolov nam omogoča sočasni dostop naprav do brezžičnega omrežja 802.11a/b/g?
Which of the following protocols enables multiple access in wireless 802.11a/b/g networks?
| Vrstica | Odgovor |
|---|---|
| TDMA | ❌ ne drzi |
| LLC | ❌ ne drzi |
| CSMA/CD | ❌ ne drzi |
| CSMA/CA | ✅ drzi |
| FDMA | ❌ ne drzi |
Quote
Carrier-sense multiple access with collision detection (CSMA/CD) is a media access control (MAC) method used most notably in early Ethernet technology for local area networking. It uses carrier-sensing to defer transmissions until no other stations are transmitting.
Beacon frames¶
Okvirji Beacon so v omrežjih 802.11 vedno šifrirani.
Beacon frames are always encrypted in 802.11 networks.
| Vrstica | Odgovor |
|---|---|
| True | ❌ ne drzi |
| False | ✅ drzi |
Okvir Ethernet¶
Okvir Ethernet ima fiksno dolžino.
Ethernet frame has a fixed length.
| Vrstica | Odgovor |
|---|---|
| False | ✅ drzi |
| True | ❌ ne drzi |
ARP je "varen"¶
Protokol ARP je varen protokol (težko ga je napasti).
ARP is a safe protocol that is hard to exploit.
| Vrstica | Odgovor |
|---|---|
| False | ✅ drzi |
| True | ❌ ne drzi |
802.11a/b/g in half-duplex¶
V brezžičnih omrežjih 802.11a/b/g poteka prenos podatkov v half-duplex načinu.
Data is transffered in half-duplex mode in 802.11a/b/g wireless networks.
| Vrstica | Odgovor |
|---|---|
| True | ✅ drzi |
| False | ❌ ne drzi |
MAC ff:ff:ff:ff:ff:ff¶
Strojni naslov ff:ff:ff:ff:ff:ff je:
The ff:ff:ff:ff:ff:ff MAC address is a:
| Vrstica | Odgovor |
|---|---|
| broadcast naslov | ✅ drzi |
| multicast naslov | ❌ ne drzi |
| anycast naslov | ❌ ne drzi |
| neznan naslov | ❌ ne drzi |
Enterprise grade switches¶
Uporabljamo napredna ustrezno skonfigurirana stikala (t.i. "Enterprise grade" ). Če okvir Ethernet pošljemo na naslov multicast, ga bomo poslali:
We are using properly configured "enterprise grade" switches. If we send an Ethernet frame to a multicast address, we are sending it to:
| Vrstica | Odgovor |
|---|---|
| Vsem računalnikom v omrežju. | ❌ ne drzi |
| Dvema računalnikoma. | ❌ ne drzi |
| Nobenemu računalniku. | ❌ ne drzi |
| Skupini računalnikov, ki je prijavljena v naslovljeno skupino. | ✅ drzi |
| Enem računalniku. | ❌ ne drzi |
Gigabit in full duplex¶
Gigabitna omrežja Ethernet omogočajo full duplex prenos podatkov.
Gigabit Ethernet networks are full duplex networks.
| Vrstica | Odgovor |
|---|---|
| True | ✅ drzi |
| False | ❌ ne drzi |
Packet sniffin' promiscuous nic¶
Če mrežno kartico postavimo v način promiscuous lahko prisluškujemo celotnemu prometu na omrežju kjer so računalniki priključeni v razdelilnik (hub).
If the computers are connected to a hub we will be able to see all the network traffic if we enable promiscuous mode on our network interface.
| Vrstica | Odgovor |
|---|---|
| True | ✅ drzi |
| False | ❌ ne drzi |
Proto za dostop do Eth¶
Kateri od naštetih protokolov nam omogoča sočasni dostop naprav do omrežja Ethernet?
Which of the following protocols enables multiple access in Ethernet networks?
| Vrstica | Odgovor |
|---|---|
| CSMA/CA | ❌ ne drzi |
| CSMA/CD | ✅ drzi |
| LLC | ❌ ne drzi |
| FDMA | ❌ ne drzi |
| TDMA | ❌ ne drzi |
Eth frame to broadcast¶
Če okvir Ethernet pošljemo na naslov broadcast, ga bomo poslali:
If we send an Ethernet frame to the broadcast address, we are sending it to:
| Vrstica | Odgovor |
|---|---|
| Nobenemu računalniku. | ❌ ne drzi |
| Dvema računalnikoma. | ❌ ne drzi |
| Vsem računalnikom v omrežju. | ✅ drzi |
| Skupini računalnikov, ki je prijavljena v naslovljeno skupino. | ❌ ne drzi |
| Enem računalniku. | ❌ ne drzi |
Posiljamo na 00:15:c5:ec:08:3f¶
Če iz našega računalnika pošljemo okvir Ethernet na naslov 00:15:c5:ec:08:3f, pošiljamo:
What kind of traffic are we sending if we sent an Ethernet frame from our computer to the Ethernet address 00:15:c5:ec:08:3f:
| Vrstica | Odgovor |
|---|---|
| Neznan promet na neznan naslov. | ❌ ne drzi |
| Broadcast promet. | ❌ ne drzi |
| Multicast promet. | ❌ ne drzi |
| Unicast promet. | ✅ drzi |
BSS ID¶
Naslov brezžičnega omrežja BSS ID je:
The BSS ID of a wireless newtork is:
| Vrstica | Odgovor |
|---|---|
| varnostni mehanizem. | ❌ ne drzi |
| strojni (MAC) naslov. | ✅ drzi |
| ime omrežja, ki si ga izmislimo, npr. linksys. | ❌ ne drzi |
| prejemnikov naslov. | ❌ ne drzi |
zastavica Protected¶
Kakšen je pomen zastavice Protected v glavi okvirja 802.11?
What does the Protected flag in the 802.11 header stand for?
| Vrstica | Odgovor |
|---|---|
| Zastavica pomeni, da so podatki v tem okviru šifrirani. | ✅ drzi |
| Zastavica pomeni, da uporabljamo požarni zid. | ❌ ne drzi |
| Zastavica pomeni, da je okvir Beacon šifriran. | ❌ ne drzi |
Quote
The Protected Frame field is 1 bit in length. The Protected Frame field is set to 1 if the Frame Body field contains information that has been processed by a cryptographic encapsulation algorithm. The Protected Frame field is set to 1 only within data frames and within management frames of subtype Authentication, and individually addressed robust management frames. The Protected Frame field is set to 0 in all other frames. When the Protected Frame field is equal to 1, the Frame Body field is protected utilizing the cryptographic encapsulation algorithm and expanded as defined in Clause 11. The Protected Frame field is set to 0 in Data frames of subtype Null Function, CF-ACK (no data), CF-Poll (no data), CF-ACK+CF-Poll (no data), QoS Null (no data), QoS CF-Poll (no data), and QoS CF-ACK+CF-Poll (no data) (see, for example, 11.4.2.2 and 11.4.3.1 that show that the frame body needs to be 1 octet or longer to apply the encapsulation).
Posiljanje okvirja¶
V omrežju imamo računalnike A, B, C, D, ki so povezani na stikalo (switch). Vsi računalniki so prej že komunicirali med seboj. Računalnik A pošlje okvir računalniku B. Kateri računalniki bodo prejeli okvir? Vse mrežne kartice so v načinu promiscuous.
Computers A, B, C, D are connected to a switch. All computers have already send and received frames from each other. Computer A sends out a frame with the destination of computer B. Which computers receive the frame? All network interfaces are in promiscuous mode.
| Vrstica | Odgovor |
|---|---|
| B, D. | ❌ ne drzi |
| B, C, D. | ❌ ne drzi |
| B. | ✅ drzi |
| C. | ❌ ne drzi |
| C, D. | ❌ ne drzi |
Kratica za šifriranje¶
Katere od spodnjih kratic označujejo šifriranje podatkov v brezžičnih omrežjih?
Which of the following abbreviatons stand for wireless network encryption?
| Vrstica | Odgovor |
|---|---|
| WEP | ✅ drzi |
| IPSEC | ❌ ne drzi |
| WPA2 | ✅ drzi |
| CryptoLink (tm) | ❌ ne drzi |
| WPA | ✅ drzi |
Vodovodna cev¶
Za vodovodno cev bi lahko rekli, da omogoča half-duplex "prenos" vode.
One could say that a water pipe is half-duplex water transport media.
| Vrstica | Odgovor |
|---|---|
| True | ✅ drzi |
| False | ❌ ne drzi |
Quote
Half duplex can not send and receive at the same time. It also has algorithms to detect and handle collisions (CSMA-CD). Think of it like a walkie talkie or a CB radio, only on a network.
Full duplex can send and receive at the same time. Think of it as a telephone.
naslov¶
V omrežju imamo računalnike A, B, C, D, ki so povezani na razdelilnik (hub). Računalnik A pošlje okvir na naslov ff:ff:ff:ff:ff:ff. Kateri računalniki bodo prejeli okvir? Vse mrežne kartice so v načinu promiscuous.
Computers A, B, C, D are connected to a hub. Computer A sends out a frame with the destination addres ff:ff:ff:ff:ff:ff. Which computers receive the frame? All the network interfaces are in promiscious mode.
| Vrstica | Odgovor |
|---|---|
| D. | ❌ ne drzi |
| C, D. | ❌ ne drzi |
| B, D. | ❌ ne drzi |
| B, C, D. | ✅ drzi |
| C. | ❌ ne drzi |
Info
Omrežje s skupinskim medijem pomeni, da vse naprave vidijo celoten omrežni promet, ne glede na to, kdo ga pošilja. Privzeto naša mrežna kartica odfiltrira vse, kar ni namenjeno našemu naslovu (ali pa na naslov broadcast). Če kartico prestavimo v promiscuous mode (to omogoča večina mrežnih kartic), izklopimo ta filter in lahko vidimo celotni promet, ki prispe do naše mrežne kartice.
Če imamo omrežje z razdelilnikom (hub), torej lahko vidimo celotni promet na omrežju. Kaj pa omrežja s stikalom? “Filter” tukaj postane stikalo, saj posreduje promet le med računalniki, ki dejansko komunicirajo med seboj.
Skrivanje SSID-ja¶
Skrivanje SSID je dobra zaščita brezžičnega omrežja.
Hidding the SSID is good protection for your wireless newtork.
| Vrstica | Odgovor |
|---|---|
| True | ❌ ne drzi |
| False | ✅ drzi |
Switch in ff:ff:ff:ff:ff:ff¶
V omrežju imamo računalnike A, B, C, D, ki so povezani na stikalo (switch). Računalnik A pošlje okvir na naslov ff:ff:ff:ff:ff:ff. Kateri računalniki bodo prejeli okvir? Vse mrežne kartice so v načinu promiscuous.
Computers A, B, C, D are connected to a switch. Computer A sends out a frame with the destination address ff:ff:ff:ff:ff:ff. Which computers receive the frame? All the network interfaces are in promiscious mode.
| Vrstica | Odgovor |
|---|---|
| D. | ❌ ne drzi |
| C, D. | ❌ ne drzi |
| B, C, D. | ✅ drzi |
| C. | ❌ ne drzi |
| B, D. | ❌ ne drzi |
huub¶
V omrežju imamo računalnike A, B, C, D, ki so povezani na razdelilnik (huub). Računalnik A pošlje okvir računalniku B. Kateri računalniki bodo prejeli okvir? Vse mrežne kartice so v načinu promiscuous.
Computers A, B, C, D are connected to a hub. Computer A sends out a frame with the destination od computer B. Which computers receive the frame? All the network interfaces are in promiscious mode.
| Vrstica | Odgovor |
|---|---|
| B, D. | ❌ ne drzi |
| C, D. | ❌ ne drzi |
| B, C, D. | ✅ drzi |
| B. | ❌ ne drzi |
| C. | ❌ ne drzi |