Navigace

Edit the page and hit Save. See syntax for Wiki syntax. Please edit the page only if you can improve it. If you want to test some things, learn to make your first steps on the playground.

====== ST1 - poznamky ======

===== RIP =====

* Nahozeni:<code>
Router# router rip
Router(config-router)# network 1.2.3.4
</code>
  * updates 30 s
  * UDP/520
  * request(ask a neighbour) a response(mine routes) message
  * AD 120 - the worst
  * ''Router# debug ip rip''
  * ''Router# show ip protocols''
  * boundary router - sits on two different classful networks
  * ''Router(config-router)# default-information originate'' propagate default route
  * ''Router(config-router)# redistribute static'' - propaguje staticky routy
  * nefunguje VLSM, CIDR ani discontiguous site (proste rozhazeny na ruznejch mistech)
  * proste ta sumarizace to pokazi a z kazdy strany prijde stejna adresa site a router aplikuje load balancing. proto pujde kus paketu tam, kus tam a pulka se vzdycky ztrati
  * IOS - defaultne prijima v1 i 2, odesila v1
  * Timery
    - Invalid - nebyl prijat update pro nejakou sit - default 180s
    - Flush - 240s - po teto dobe je routa odstranena uplne
    - Holddown - 180s - zajistuje prechodnou dobu po vypadku nejakeho interfacu

===== RIPv2 =====

* multicasty misto broadcastu
  * VLSM, CIDR a tak, pozor, automaticky sumarizace jsou porad na classfull, takze nepouzitelny, vypnout ''no auto-summary'' v Router(config-router)#.
  * navic (info v RIPv2 segmentu)
    * posila masku
    * posila next-hop - tj kam to pujde z odesilateskyho routeru, slouzi pro optimalizace routy
  * ''Router(config-router)# version 2''

===== Misc =====

* null0 - interface pro zahazovani paketu, dobry pro sumarizace neuplnejch siti, da se tam normalne nasmerovat route, automaticky to tam strka eigrp pri sumarizaci.
  * ''show ip interface brief'' ukaze prirazeni IP a stav zarizeni

===== EIGRP =====

* metrika: bandwidth, delay, reliability(spolehlivost), load (zatez) - spolecne s IGMP
  * defaultne jen bandwidth a delay   
  * DUAL (Difussing Update ALgorithm)
  * nema periodicke updaty, nepouziva aging (narozdil od IGRP)
  * ma vlastni tabulku s topologii, takze muze spocitat zalozni cesty (narozdil od IGRP)
  * Hello protokol - zjistovani sousedu (mensi zatez linky), triggered updaty (jen pri zmene stavu)  
  * zabaleno v IP paketu, protokol 88, posila se multicastem 224.0.0.10
  * 4 typy zprav
    * update - zmena stavu site - multicast
    * ACK - pri pouziti spolehliveho odeslani (vse krome Hello) - na unicastovou adresu
    * query - pouziva DUAL pro hledani siti a jine ucely - multicast 
    * reply - odpoved na query - unicast
    * hello - objevovani sousedu
  * v segmentu je pole TLV - type/length/values - obsazuje metrikama, internal/external(jiny autonomni system) IP
  * PDP - protocol dependent modules - zvlada i IPX, AppleTalk
  * Pakety dorucuje pomoci RTP (Reliable Transport Protocol), cili nezavisi na TCP/IP, ale lze provozovat i nad IPX, AppleTalk                         
  
  * **Hello**
     * interval 5s, na uchylackejch sitich (ATM, FrameRelay, X25) 60s
     * holdtime - interval, kdy se oznaci nod jako nedostupny, defaultne 3x interval Hello

* partial update - posila se jen zmena stavu
  * bounded update - jen tem, kterych se to tyka
  * AD 90 (internal), 170 (external sources, napr. default GW), 5 pro summary routes
  * Autonomni system - kus site, spravovano jednou organizaci, mezi AS se routuje exterior gateway routing protocoly, napr BGP.
  * ''router eigrp 1'' - 1 je oznaceni AS i procesu, ale neni to skutecne cislo AS
  * ''Router(config-router)# network A.B.C.D'' - classful, podsite se urcuji wildcardem, coz je negace masky (1 = don't care)
  * ''show ip eigrp neighbors''
  * null0 routa - kdyz je zapnuta automaticka sumarizace aspon jedna podsit je naucena pres EIGRP - aby to zahazovalo zbytecny pakety   
  * vahy metriky (k1-k5), pro urceni vysledne metriky z dilcich, defaultne je zapnuta K1 (bandwidth) a K3 (delay). K2(load). K4,5 - reliability
  * ''Router(config-router)# metric weights tos k1 k2 k3 k4 k5'' , tos = 0, nebylo implementovano
  * reliability a load - zlomky z x/255
  * ''Router(config-router)# bandwidth //kilobits//''

==== DUAL ====

* sucessor - next hop na nejlevnejsi ceste (takovy to via v show ip route)
  * feasible distance (FD) - nejnizsi spoctena cena cesty, je uvedena v ''show ip route'' jako druha v hranatych zavorkach
  * feasible successor - soused, ktery ma cestu do stejne site a splnuje feasibility condition
  * feasibility condition - je splnena, pokud "nahradni router" hlasi svou vzdalenost (reported distance) nez je feasibility distance do site z routeru, ktery resi nahradni cestu.
  * reported distance - feasibility distance, kterou hlasi router ostatnim routerum
  * ''show ip eigrp topology'' - ukazuje dostupne site (Aktivni-pocita se/pasivni-je spocitana) a nasledniky pro jejich dosazeni. Prvni successor je ten, ktery se pouzije normalne, metriky jsou FD/RD. Dalsi je feasible successor, metriky FD/RD. FD je takova, jaka by byla kdyby se stal successorem. 
  * ''show ip eigrp topology A.B.C.D'' - detailnejsi info.
  * ''show ip eigrp topology all-links'' - vypise i hopy, ktere nesplnuji FC
  * ''debug eigrp fsm'' - stav automatu DUALu                  
  * Pokud nejsou feasible successors, sit v topologii se prepne do aktivniho stavu a posilaji se queries k sousedum, jestli nemaji cestu do teto site.
  * manualni sumarizece na kazdem odchozim interface: ''Router(config-if)#ip summary-address eigrp as-number network-address subnet-mask''. Staci zadat adresu toho CIDR, postizene site se urci samy.
  * ''Router(config-if)#ip bandwidth-percent eigrp as-number percent'' - kolik ve skutecnosti hlasi eigrp bandwidth
  * ''Router(config-if)#ip hello-interval eigrp as-number seconds''
  * ''Router(config-if)#ip hold-time eigrp as-number seconds''

===== Link State algoritmy =====

- Zjisti pripojene site
  - Pomoci Hello zjisti sousedy
  - Vytvori LSP (Link State Packet)
    * The interface's IP address and subnet mask.
    * The type of network, such as Ethernet (broadcast) or Serial point-to-point link.
    * The cost of that link.
    * Any neighbor routers on that link.
  - Posila pres sousedy po siti (Flooding)
  - Kazdy router si sestroji svoji mapu topologie (SPF aka Dijkstra)
  
  * LSP se neodesilaji periodicky - jen pri inicializaci a pak pri zmene
  * Pouziva Aging a sekvencni cisla, aby se dalo urcit, ze tenhle paket uz tady byl

===== OSPF =====

* metrikou je bandwidth
  * area - kus site, pro kterou si sestavuje prislusny router topologii
  * AD 110 (horsi nez internal EIGRP, lepsi jak external EIGRP a RIP)  
  * ospf zabalen do IP paketu, protokol 89, multicast 224.0.0.5(6)
  * 5 druhu paketu
    - Hello   
    - DBD - database description - obsahuje vycuc z link-state databaze odesilajiciho serveru, slouzi pro kontrolu informaci na cilovem routeru
    - LSR - link state request - pozadavek o informaci
    - LSU - odpoved na LSR nebo oznameni noveho stavu
    - LSAck - potvrzeni prijmu LSU
  * **Hello**
    * zjistuje sousedy
    * distribuuje parametry "sousedskych vztahu"
    * voli Designated Router (DR) a Backup DR na sitich se sdilenym pristupem (Ethernet, Frame Relay)
    * Interval Hello paketu: 10s na multiaccess sitich a dvoubodovych spojich, 30s na ne-broadcastovych sitich (Frame Relay, ATM)
    * dead interval - 40s normalne, 120s exoticky site
  * **LSU**
    * Muze obsahovat az 11 typ Link State advertisements 
  * **Link state** je v podstate popis rozhranni a jeho vyznam/vztah k ostatnim routerum.
  * ''R1(config)#router ospf 1'', kde 1 je process-id
  * ''Router(config-router)#network //network-address wildcard-mask// area //area-id//'' - na nekterych verzich IOS jde pouzit i maska
  * RouterID - je to ID routeru ve tvaru IP adresy, prikaz ''router-id'', kdyz neni, vezme se nejvyssi IP adresa ze vsech loopbacku, kdyz neni loopback, vezme se nejvyssi IP z nahozenych interfacu
  * ''show ip protocols'', ''show ip ospf'', ''show ip ospf interface'' - vypise taky routerID
  * ''Router#clear ip ospf process'' - restartne vyber RouterID
  * ''show ip ospf neighbour''
  * SPF schedule delay - cas, ktery se ceka na zahajeni vypoctu SPF, kvuli sitim neustale menicim svuj stav, defaultne 5s
  * Hold time - minimalni doba mezi vypocty SPF - defaultne 10s
  * ** metrika **- cost, pocita se jako 10^8/bandwidth v bps, 1= 100Mbit a vyssi
    * pro vetsi rychlosti mozno nastavit ''auto-cost reference-bandwidth''
    * scitaji se pro vyslednou routu
    * ''# show interface'' - dozvime se tam bandwidth, ktery se pocita pro vypocet cost, nemusi odrazet aktualni rychlost interfacu
    * ''# show ip ospf interface'' - vypise treba i cenu spoje
    * ''Router(config-if)#bandwidth //bandwidth-kbps//'' - zmena bandwidth (dobre pro seriaky, kde vzdy nemusi bezet stejne rychle) a dusledkem toho i cost.
    * ''R1(config-if)#ip ospf cost 1562'' - specifikuje cenu primo, dobre pro multi-vendor prostredi
    
  * OSPF defines five network types:
    - Point-to-point 
    - Broadcast Multiaccess 
    - Nonbroadcast Multiaccess (NBMA) - Frame Relay, ATM, X.25 
    - Point-to-multipoint 
    - Virtual links
  * multiaccess site delaji problem s floodingem - hafo paketu -> Designated router
  * **Designated router** + backup DP - rozesilaji LSA od nejakeho jineho routeru vsem, ''show ip ospf neighbor'' ukaze i role routeru, DROTHER je ten pasivni (co jen posila updaty k (B)DR
    * urcuji se pomoci priorit, pak podle RouterID    
    * ''show ip ospf interface fastethernet 0/0'' - nejaky info o interface
  * DR a BDR se vybiraji jednou, kdyz se prida novy router s vyssi prioritou, takze je nutno povypinat interfacy na ostatnich, nebo dat reload, proste zajistit, aby nas vyvoleny nabootoval prvni.
  * ''Router(config-if)#ip ospf priority {0 - 255}''
  * ''R1(config-router)#default-information originate'' - propagace defaultni routy
  * ''R1(config-router)#auto-cost reference-bandwidth 10000'' - v megabits/s
  * ''Router(config-if)#ip ospf hello-interval //seconds//''
  * ''Router(config-if)#ip ospf dead-interval //seconds//''

Please fill all the letters into the box to prove you're human. O L Q I J Please keep this field empty:

Edit summary

st1.txt · Last modified: 2011/08/16 22:33 (external edit)

Back to top