Static and Default Routes

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4 Categories of routing table entries:

• directly connected routes
  • for subnets for which the router has a local interface
• remote routes
  • for subnets and IP networks that are not directly attached
• host routes
  • to a specific IP address
  • host route has a /32 (IPv4) or /128 (IPv6) prefix
• default route
  • to use when an exact match for a network or host route is not found

Directly Connected Routes

• IP network or subnet for each active router interface is automatically added to the routing table
  • known as directly connected routes

Static Routes

• static route is manually added to the routing table
• only changes if edited by the administrator
• useful in some circumstances
• can be problematic if the routing topology changes often
  • each route on each affected router needs to be manually updated

Info

• static routes can be configured as non-persistent or persistent/permanent
• non-persistent route is removed from the routing table if the router is rebooted
  • might be added as a troubleshooting action
• if a static route is not reachable, it will be disabled

Default Route

A default route is a special type of static route that identifies the next hop router for a destination that cannot be matched by another routing table entry.

• default route address:
  • IPv4 0.0.0.0/0
  • IPv6 ::/0
• described as the gateway of last resort
• most end systems are configured with a default route
  • pointing to the default gateway
• may be the simplest way for an edge router to forward traffic to an ISP’s routers