studyQuestions6/7

24 flashcards · Other · by Emanuel Gostner

1. Why do we need an inter-network protocol?

   To connect multiple L2 networks

2. Name some functions performed by IP

   Logical addressing connection of L2 networks fragmentation

3. What are some functions IP does NOT include?

   Error control ACKs Retransmission Reliability Flow control

4. Does IP guarantee delivery?

   No, IP is best effort. Error correction happens either on L4 (ex. TCP) or L7 (ex. TFTP)

5. Difference Routed /Routing protocol

   Routed: IP Routing: RIP, OSPF, EIGRP. Needs logical addressing to send packets (get them from routed protocol)

6. descript direct / indirect delivery

   direct delivery: packet sent to a host inside the local network indirect delivery: packet sent to a host outside the local network

7. Size of an IP-packet

   between 20 <-> 65535 bytes (2^16-1)

8. IPv4 Protocol header field. Name UDP/TCP ID

   ID of the upper layer protocol. TCP: 6 UDP: 17

9. Difference limited / directed broadcast

   directed broadcast: 192.168.0.255/24 sends packet to all host in this subnet limited broadcast: 255.255.255.255 no routable. sends packets only to hosts in local network. Router does not forward these packets

10. Difference Network MTU size and Maximum TCP packet size

    Network MTU size: limited by hardware Max. TCP Packet size: can be set manually (should not be higher than MTU size). Normally set to 1500 bytes

11. where is reassembly done?

    at the destination

12. Is the payload part of the header

    no. Only the fields before and after (trailer) are part of the header <header><payload><header (trailer)>

13. What is the ARP cache / ARP table

    Cache: generated IP<-> MAC relations are stored on host devices. Table: manually set IP<->MAC relations on L3 devices

14. dest. address of ARP-request

    L2 broadcast (FFFF:FFFF:FFFF:FFFF) with the required IP in its payload

15. ICMP responsibilites. To which Protocol attached?

    Internet control message protocol send control messages send error messages ICMP is in the IP payload

16. Header of ICMP

    depends on the ICMP-message type echo reply (used by the OS utility ping) destination unreachable time exceeded

17. what is vlan trunking

    Switches use vlan tagging if trunking is activated

18. Default vlan

    by default all ports are placed in a particular vlan (aut. Vlan 1)

19. native vlan and purpose

    the protocol 802.1Q does not add a vlan header to frames in the native vlan (untagged). By default this is vlan 1. If the receiving switch sees a frame without tag it knows its part of the native vlan. Cause of that both switches have to agree on the native vlan. Purpose: is to support legacy devices that don’t understand trunking (tagging)

20. management vlan

    management traffic should be in own network. SVI interface defined with IP. Default vlan 1

21. vlan security precautions

    change the standard default/native/management vlan since they are all vlan 1 disable unused ports

22. What is the problem of switching loop?

    broadcast storm constant rewriting of mac-table

23. 4 states of switches (STP)

    blocking listening learning forwarding

24. port roles (STP)

    Designated port Root port Non-designated port / alternate port