Help
Options
Didn't know it?
click below
click below
Knew it?
click below
click below
Don't Know
Remaining cards (0)
Know
retry
shuffle
restart
0:00
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
N+ 5.Troubleshooting
5 > Network Troubleshooting
| Term | Definition |
|---|---|
| Network Troubleshooting IED EIV | - id the problem - establish a theory - test theory - evaluate results - plan of action - implement plan - verify system functionality - document findings |
| Establish Theory | Examine the problem from the OSI top to bottom |
| Using the Right Cable | - speed/bandwidth - throughput - distance |
| Cable Abbreviations | U-unshielded S-braided shielding F-foil shielding (Overall cable) / (individual pairs)TP - braided shielding with foil around the pairs S/FTP - foil around the cable and no shielding around the pairs F/UTP |
| Plenum-rated cable | - PVC - fire rated cable jacket - |
| Serial Console Cables | D-sub - serial communications standard |
| Rollover cable | RJ45 to serial standard |
| Ethernet Cross-over cables | - connect to ethernet devices without using a switch - |
| PoE | Power of Ethernet - power provided on an Ethernet cable - power provided at the switch |
| Attenuation | - loss of signal intensity as signal moves through a medium |
| dB Decibals | - signal strength ratio measurements |
| dB loss symptoms | - no connectivity - intermittent connectivity - poor performance -- signal too weak -- CRC errors, data corruption |
| Incorrect pin-out | - near and far pins in cables aren't where they are supposed to be - performance or connectivity issues |
| Bad ports | - interface errors |
| Incorrect Transceivers | - trans have to match the fibre -- single mode trans connects to single mode fibre - trans need to match the wavelength -- 850nm etc |
| Duplex/Speed Mismatch | - speed: 10/100/1000/auto - duplex: half/full/auto - incorrect speed -- many switch configs will auto-neg speed - incorrect duplex -- auto-neg -- needs to match on both sides -- mismatch significant slowdowns |
| TDR | Time Domain Reflectometre - troubleshoot opens / shorts |
| Reversing Transmit and Receive | wiring mistake - easy to find with a wire map -- 1-3, 2-6, 6-2 -- some network interfaces auto correct (A uto-MDIX) |
| Cable Crimpers | "pinch" the connector onto a wire -- coaxial, twisted pair, fibre - connect the modular connector to the Ethernet cable |
| Punch-down tools | "punch" a wire into a wiring block - 66 / 110 block |
| Tone Generator | - where does the wire go? -- follow the tone -- puts an analog sound on the wire - Inductive probe -- doesn't need to touch the copper |
| Loopback plugs | - useful for testing physical ports -- or fooling your applications - serial - network connections - NOT cross-over cables |
| TDR / OTDR | Time Domain Reflectometer / Optical - estimate cable lengths - identify splice locations - cable impedance info - signal losses - locate copper or fibre breaks |
| The TDR | - sends an electrical pulse down the cable - impedance discontinuities case a reflection -- TDR calculates time and distance -- OTDR does the sam with light |
| Multimetres | AC - check wall outlet voltage DC - PC power supply output voltages - CMOS battery power Continuity - cable connectivity - fuse status - wire mapping |
| Cable Testers | - continuity test - simple wire map - can identify missing pins or crossed wires |
| Taps and Port Mirrors | - intercept network traffic - physical taps - port mirror -- port redirection, SPAN (Switched Port Analyzer) -- software based tap |
| Fusion Splicer | - join two ends of a fibre together -- minimal light loss, low reflection - extend the length - add a connector to the end - remove a damaged section |
| Light Meter | - sometimes you just need to know how much light is getting through -- one of the most mportant things to know when installing fibre equipment |
| Traceroute | - tracert WIN - traceroute LINUX - determine the route a packet takes to a destination -- takes advantage of ICMP TTL exceeded error message |
| ARP | - determine a MAC address based on an IP address arp -a - view local ARP table |
| netstat | network statistics netstat -a - show all active connection netstat -b - show binaries (WIN) netstat -n - do not resolve names |
| route | - view the devices routing table -- find out which way the packets will go WIN: route print LINUX: netstat -r |
| tcpdump | - capture packets from command line - most LINUX systems - WIN: windump - apply filters, view in real-time - written in standard pcap format |
| basic platform commands | - show interface -- view the interfaces on a device -- view detailed interface info -- show config - view the device config / show run -- show route -- view the routing table / show ip route |
| hostname | - view the FQDN and |
| RSSI | Received Signal Strength Indication - measured in dBm (decibal-milliwatts) - shown as negative number on a log scale -- closer to zero is better |
| EIRP | Effective Isotropic Radiated Power - the radiated signal strength -- transmit strength + antenna gain - cable loss |
| Attenuation | Wireless signals get weaker as you move farther from the antenna - measured with a WiFi analyzer - control the power output on the access point - use a receive antenna with a higher gain -- capture more of the signa |
| Security Type Mismatch | - encryption on wireless is important -- make sure the client matches the access point |
| Device Configuration Review | - don't start blindly troubleshooting - view the configuration -- native desktop or web based console -- ssh/terminal console - try getting the configuration ahead of time |
| Interface Status | - know details of important interfaces - check easy stuff first -- verify physical connectivity |
| VLAN Assignment | - network link is active and IP address is assigned -- no access to resources or limited functionality - every switch interface is configured as an access port or a trunk port -- each access port is assigned to a VLAN |
| Collisions | - half duplex > collisions are normal - interface config issues -- duplex mismatch - hardware issue -- could indicate bac NIC or bad driver |
| Troubleshooting Broadcast Storms | - packet capture -- id the device - research the process that's broadcasting -- there may be another option - separate the network into smaller bc domains -- change one large subnet to many smaller routed subnets |
| Duplicate MAC Addresses | - may be an on-path attack - mistakes can happen - intermittent connectivity -- confirm with packet capture - use ARP command from another computer -- confirm MAC matches IP |
| Duplicate IP addresses | - static assignments must be very organized - DHCP isn't a panacea -- multiple DHCP servers overlap -- rogue DHCP servers |
| IGMP snooping | Internet Group Management Protocol -- hosts and routers use this to direct multicast transmissions - switches can watch for these messages -- switch then intelligently forwards multicasts to those specific devices Enable IGMP snooping |
| Rogue DHCP server | - disable rouge DHCP comms -- enable DHCP snooping on switch -- authorized DHCP servers in Active Directory - disable the rogue -- renew the IP leases |
| Exhausted DHCP scope | - client received an APIPA address -- local subnet comms only - check the DHCP server -- add more addresses if possible |
| IP Configuration Issues | - communicate to local IP addresses -- but not outside subnets - no IP comms -- local or remote - communicate to some IP addresses -- but not others |
| IP Configuration Issues II | - check documentation -- IP address, subnet mask, gateway, DNS - monitor the traffic - traceroute and ping |
| DNS Issues | - is the DNS IP address correct? - use nslookup or dig to test -- does resolution work? - try a different server -- 8.8.8.8 |
Created by:
jwjwj
Popular Computers sets