What is a static host route, and when are host routes automatically created?

A static host route is a route to a single specific IP (Internet Protocol) address — using a /32 mask (IPv4) or /128 prefix (IPv6). Host routes are automatically created for every IP address configured on a router interface (the "L" local routes).

Manually configured static host route:

! IPv4 — route to a specific server
R1(config)# ip route 209.165.200.238 255.255.255.255 198.51.100.1

! IPv6 — route to a specific host
R1(config)# ipv6 route 2001:db8:acad::238/128 2001:db8:acad:1::2

When to use static host routes:

• Direct traffic to a specific server via a particular path
• Create a route for a management station or syslog server
• Override a less-specific route for one particular host

Automatically installed host routes (Local routes):

R1# show ip route
L    192.168.1.1/32 is directly connected, GigabitEthernet0/0
L    172.16.2.1/32 is directly connected, Serial0/1/0

• Created automatically when an interface is configured with an IP and goes up/up
• IPv4 local routes use /32 (matches exactly one IP)
• IPv6 local routes use /128 (matches exactly one IPv6 address)
• Purpose: efficiently identifies packets destined for the router itself (management traffic, routing protocol hellos, etc.)

Tip: Host routes always win in longest-prefix-match because /32 (or /128) is the longest possible prefix — nothing can be more specific.

Go deeper:

• Longest prefix match (Wikipedia) — why a /32 or /128 always wins, the property that makes host routes override everything.