Number of parallel routes (equal cost paths):

  • 6 for Cisco IOS Release < 12.3(2)T
  • 16 for Cisco IOS Release ≥ 12.3(2)T

Comment choisir une route dans la table de routage:

  1. Choose the most specific Network Mask for the destination network
  2. Choose the Best Administrative Distance
  3. Choose the metric

Administrative distance

Protocol Administrative distance
Directly connected 0
Static route out an interface 0
Static route to a next-hop address 1
EIGRP summary route 5
External BGP 20
Internal EIGRP 90
IGRP (IGRP is no longer supported, as of Cisco IOS Release 12.3) 100
OSPF 110
IS-IS 115
RIP 120
EGP 140
ODR 160
External EIGRP 170
Internal BGP 200
Unknown 255

Protocols, Ports, and Reliability of Routing Protocols

Routing Protocol Protocol Number Port Number Update Reliability
IGRP (IGRP is no longer supported, as of Cisco IOS Release 12.3) 9 - Best-effort delivery
EIGRP 88 - 1-to-1 window
OSPF 89 - 1-to-1 window
RIP - UDP 520 Best-effort delivery
BGP - TCP 179 Uses TCP windowing

Pour rappel, concernant la couche transport, les numéros de protocole de TCP et UDP sont:

  • TCP = 6
  • UDP = 17