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Puškice za dinamičke ruting protokole


  • Tables:
    – neighbour table
    – topology tabel
    – IP routing table
  • Neighbourship configuration
    1) Basic EIGPR configuration
    2) Named EIGRP configuration
    3) Hello/hold timer – they don’t have to match, but hello timer must be lower than neighbours dead timer
    4) Passive interface
    5) Authentication (mode, key-chain, key-string)
    6) Distribute list in/out (with route-map, prefix-list, access-list) – filtering of routes advertised to other routers or blocking from receving routes
    7) Offset list in/out (with route-map, prefix-list, access-list) – with this we change metric
    8) Variance (FS route metric < S route metric x variance) – multiple routes in RIB for same destination
    9) Summary address; leak map (route-map, prefix-list, access-list)
    10) Stub router (connected, summary, static, specific interface) – routers in this area won’t receive any route but it will advertise one of types specified in the paranthesies
  • Neighbourship adjacency problems
    1) Mismatched K values
    2) Mismatched AS numbers
    3) VLAN Access control list
    4) ACL (L3 ip access-list)
    5) Incorrect network statement
    6) Passive interface
    7) Authentication
    8) Incorrect subnets
    9) Interface is down
    10) Timers


  • Packet types
    1) Hello packet(contains RID,Hello intervals,DR,BDR) – multicast addresses, DR,BDR on the segment)
    2) DBD packet(contains only LSA headers)
    3) LSR packet – a packet that lists the LSIDs of LSAs that that the sender of LSR would like the receiver of the LSR to supply during database exchange
    4) LSU packet(it could be also used as LSAack)
    5) LSAack packet – confirmation of received LSU packet
  • OSPF neighbour states
    1) Down – no hellos have been recevied from this neighbor for more than the dead interval
    2) Attempt(used when the neighbour is defined with neighbour command)
    3) Init – a hello has been received from the neighbor, but it did not have the local router’s RID in it or list of parameters that do not pass the neighbor verification checks. This is a permanent state when hello parameters do not match.
    4) 2-Way – peer has seen his own router id in received hello packet, it means that neighbouring router saw him and all neighbor verification check passed.
    5) ExStart – negotiating the DBD sequence numbers and master/slave logic user of DBD packets
    6) Exchange – finished negotiating the DBD process particulars, and currently exchanging DBD packets
    7) Loading – all DBD packets are exchanged, and the routers are curently sending LSR, LSU, and LSAack packets to exchange full LSAs
    8) Full – neighbors are fully adjacent, meaning that they believe that their LSDBs for that area are identical. Routing table calcualations can begin.

OSPF network types

  • OSPF LSA types
    1) Type 1 – Router
    2) Type 2 – Network
    3) Type 3 – Network summary – routes from other areas
    4) Type 4 – Autonomous System Boundary Router (ASBR) Summary
    5) Type 5 – Autonomous System (AS) External – routes introduced from other routing protocols
    6) Type 6 – for ospf multicast
    7) Type 7 – NSSA External – external routes (LSA5) which are in NSSA area represented as LSA7
    8) Type 8 – Link(OSPFv3)
    9) Type 9 – Intra-area prefix (OSPFv3)
  • OSPF adjancencies problems
    1) Layer 1/2 is down
    2) VLAN acess-list is blocking OSPF within a VLAN (switch)
    3) Interface does not have OSPF enabled
    4) Passive interface
    5) Access-list (ACL) blocking OSPF on both sides
    6) Subner mask not matching on Broadcast segment
    7) Mismathced authentication type/key
    8) Mismatched Hello/Dead intervals
    9) Mismatched stub type
    10) Mismatched area ID
  • Neighbourship configuration
    1) Basic configuration
    2) Named mode config
    3) Timers hello/hold
    4) Passive interface
    5) Authentication (md5,plain text, after 15.6 SHA)
    6) Route filtering
    a)distribute list in (filter routes from geting into RIB;on specific router)
    b)area x filter-list prefix-list in or out of specific area(only on ABR,ASBR)
    7) Route summarization (only on ABR,ASBR)
    a)ABR-from area where they are to all other areas(area x range a.b.c.d/x cost x)
    b)ASBR-summarization of external routes T5 LSAs;(summary-address prefix mask)
    8) Default routes(default information originate)
  • OSPF Stub area types
    1) Stubby – filter only LSA5 (External routes, redistributed routes from some other routing protocol)
    2) Totaly stubby – filter LSA3 and LSA5; (LSA3 routes from other area, distributed by ABR)
    3) NSSA (Not So Stubby Area) – allow redistribution of external routes as LSA7
    4) Totaly NSSA – allow LSA5, filter LSA3
  • Best path selection
    1)We can influence which path will be choosen by seting interface subcommand -ip ospf cost xxx



Sve zasluge za tekst idu Milošu Janjiću janjic.milos81@gmail.com

About Dejan

Zaljubljenik u sve što ima veze sa mrežama, komunikacijama i bezbednošću na mreži. - 9+ godina iskustva u IT-u ( ISP, Enterprise) - Trenutno radim u mladoj perspektivnoj firmi koja nudi kompletna rešenja krajnjim korisnicima - Veliki broj kurseva iz raznih oblasti ( Routing&switching, Security,MDM, Cloud, F-Secure, CEH) - "Svi smo se našli pred problemom koji nam je neko drugi rešio. Pitanje je samo koliko brzo naiđeš na nekog ko je voljan da ti pomogne." - Ponosni otac 2 dečaka
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