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WAN Final
| Question | Answer |
|---|---|
| What is Static NAT? | Mapping a private IP address to a public IP address on a one-to-one basis |
| What is Dynamic NAT? | Mapping a private IP address to a public IP address from a pool of public IPs |
| What is Overloading? (NAT Overload) | Dynamic NAT that maps multiple private IP address to a single public IP address by using different ports. Also called PAT. |
| What is RFC 1918? | Private IP address space. 10/8, 172.16/12, 192.168/16 |
| What are the private IP addresses and prefixes? | 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16 |
| What are some advantages of NAT? | Preserve public IPv4 addresses. Adds degree of privacy/security to network. Preserves consistency of internal network design (can change the global IP address without affecting the internal). |
| Where does a NAT router typically operate? | Border of a stub network. |
| When does NAT take place? | Going between an inside and outside interfaces. |
| What is the difference between inside local and inside global addresses? | Inside local = Private source IP of local network, Inside global = Public source IP as seen from the outside network |
| When would you want to use a static NAT? | Servers that must have consistent address that is internet accessible. |
| If a packet is sent from an inside port to an outside port using port 1444 how does the NAT handle the translation? | Sets it to the inside global IP address and will try to keep the same source port of 1444 to mark which computer it came from. |
| What happens when 2 computers from an inside network send packets to outside networks using the same source port? | The router will keep the first one it receives the same port and then use a port starting from the beginning of the appropriate port group 0–511, 512–1,023, or 1,024–65,535 |
| Why is there an issue with using PAT with ICMP packets? | ICMP works at layer 3, doesn't have a layer 4 port address to use PAT with. |
| How does PAT translate an ICMP packet? | ICMP has a Query ID field which PAT uses since they don't have a port number. |
| What are disadvantages with NAT? | Network performance, some applications fail, trace issues, complicated tunneling protocols, initiating TCP connections can be interrupted. |
| Commands to set up a static NAT? | ip nat inside source static <localIP> <globalIP>; ip nat inside (on inside interface); ip nat outside (on outside interface) |
| Command: used to show active NAT translations? | show ip nat translations |
| If you have set up a static NAT use the show ip nat translations command and there are no translations listed what is wrong? | The static NAT was not set up properly, static NATs will always show up with the show command, dynamic NATs will not. |
| Command: used to show information about the total number of active translations? | show ip nat statistics; use: clear ip nat statistics, to reset them |
| How does Dynamic NAT serve IP addresses to devices? | Using a pool on a first come first serve basis. If the pool runs out and another device wants an address it will have to wait untill one becomes available. |
| Command: used to set up a pool for NAT use? | ip nat pool NAME <startIP> <endIP> netmask <netmask>; could use prefix-length <prefix> instead of netmask command |
| Command: used with dynamic NAT to set translation between access-list 1 and pool named NAME | ip nat inside source list 1 pool NAME |
| Using dynamic NAT how long will a translation remain in the table by default? | 24 hours, ip nat translation timeout # command will let you change the default |
| Command: used with PAT (or NAT overload) to set translation between access-list 1 and pool named NAME | ip nat inside source list 1 pool NAME overload |
| Command: used with PAT (or NAT overload) to set translation between access-list 1 and exit interface fa0/1 | ip nat inside source list 1 interface fa0/1 overload |
| Technique which allows an external user to reach a port on a private IPv4 address from the outside? | port forwarding |
| Command: set up port forwarding for local web server on 192.168.0.10, global ip of 209.165.200.225 | ip nat inside source static tcp 192.168.0.10 80 209.165.200.225 80 |
| What is the IPv6 version of RFC1918 IPv4 private addresses? | ULA (Unique Local Addresses), FC00::/7 |
| How is NAT for IPv6 used? | NOT like IPv4 to connect to a private IPv6 address, it is used in IPv6 to transparently provide access between IPv6 only and IPv4 only networks. Called NAT64. |
| Command: to show NAT debugging information? | debug ip nat, in this debug s= source, d= destination |
| Teleworker advantages: | productivity, reduced cost, easier recruit/retention, flexibility |
| Teleworker disadvantage: | Harder to track progress/manage, isolation, distractions, slower connections |
| Methods used for teleworking? | Broadband, IPsec VPN, private WAN technologies |
| What is DOCSIS? | Data-over-Cable Service Interface Specification - international standard developed by CableLabs. Layer 1 + 2 requirements. |
| Broadband Cable: Which end has the CMTS and which has the CM? | CMTS = Cable Modem Termination System on the operator end, CM = Cable modem on the subscriber end |
| Broadband Cable: What is S-CDMA? | Synchronous Code Division Multiple Access |
| Difference between ADSL and SDSL? | ADSL = Asymmetrical, More download than upload. SDSL = Symmetrical, same download and upload |
| Advantage & Disadvantage of DSL? | Non shared medium, length of local loop decreases speeds |
| Advantage & Disadvantage of Cable? | shared medium, distance not a concern |
| What is microfilter used for in DSL? | Seperate the voice channel from the data. |
| Why is PPP still being used by ISPs? | Ability to assign an IP address to link giving customer an IP, CHAP authentication for customers. |
| In PPPoE what should be done with MTU? | Set down to 1492 instead of default 1500 to accommodate PPPoE headers. |
| Advantages of GRE tunnel? | Multiple protocols supported, multicast traffic |
| What are the configuration steps to setting up a GRE tunnel? | Create tunnel, set source IP/interface, set destination IP, set tunnel IP, OPTIONAL set GRE tunnel mode (default) |
| What are advantages of SSL VPN? | Web-based clientless access, does not require pre-installed software. |
| What are advantages of IPsec VPN? | more application support, stronger encryption + authentication, better security |
| Syslog: Level 0 - 7, which is the most urgent? | 0 = emergency and most urgent, 7 = debug and rarely used. |
| Syslog: %LINK-3-UPDOWN ... what does this mean? | Facility = LINK, Severity = 3, MNEMONIC = UPDOWN |
| Verify: Logging info | show logging |
| Configure: logging of level 4 and below from interface g0/0 to syslog server at 192.168.1.3 | logging 192.168.1.3; logging trap 4; logging source-interface g0/0 |
| Command: send logging messages to a telnet session? | terminal monitor |
| SNMP: where do traps, gets, and sets get configured? | trap on the agent sends messages to manager, gets and sets on manager to poll the agents |
| SNMP: where does information get stored? | MIB - management information base |
| SNMP: difference between v1, v2, and v3? | v1 = clear text, community string, v2 = community string, v3 = encryption & authentication |
| SNMP: verify command | show snmp |
| What 7 fields did original netflow monitor? | source+dest IP+port, layer 3 protocol, interface, type of service ToS marking (QoS) |
| NetFlow: display stats summary | show ip cache flow |
| NetFlow: display interface configs (egress / ingress) | show ip flow interfaces |
| NetFlow: display export config | show ip flow export |
Created by:
Datheral
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