📘 CCNA 200-301 v1.1

3.3 Configure and verify IPv4 and IPv6 static routing

3.3.c Host Route

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🔹 What is a Host Route?

A Host Route is a route to a single, specific IP address in the routing table.

It is the most specific route that can exist in an IP network because it points to one single host rather than a whole network.

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🔹 Format of a Host Route

A host route is identified by a /32 prefix length for IPv4 and a /128 prefix length for IPv6.

• IPv4 Host Route example: 192.168.10.5/32 This means only one host with IP address 192.168.10.5.
• IPv6 Host Route example: 2001:db8:abcd::1/128 This means only one host with IPv6 address 2001:db8:abcd::1.

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🔹 Why Do We Use Host Routes?

Host routes are used when you want to reach a specific device (host) instead of an entire network.

Common reasons include:

1. Network management or troubleshooting
   • You might want to reach a single device (like a network printer, firewall, or server) directly through a specific path.
2. Security and traffic control
   • Some networks restrict access and allow routes only to specific IPs for control and monitoring.
3. When there’s no need to route to the whole network
   • For example, when only one host in another network is reachable or allowed.

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🔹 Characteristics of a Host Route

Feature	Description
Prefix length	/32 (IPv4) or /128 (IPv6)
Destination	Only one IP address
Most specific route	It always has the highest priority in routing
Administrative distance and metric	Same as other static routes unless manually changed
Added manually	Usually configured manually as a static route (though can also be learned dynamically in some cases)

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🔹 How a Router Uses a Host Route

When a router receives a packet, it looks at the destination IP address and checks its routing table to find the best match.

• The router uses the Longest Prefix Match rule, meaning it prefers the route with the most specific subnet mask.
• Since a host route (/32 or /128) is the most specific possible, it always takes priority over other routes.

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🔹 Example: IPv4 Host Route Configuration

Let’s say you want to configure a static host route to reach a specific server (192.168.50.10) through a next-hop address (10.1.1.2).

Command:

Router(config)# ip route 192.168.50.10 255.255.255.255 10.1.1.2

Explanation:

• 192.168.50.10 → Destination host IP address
• 255.255.255.255 → Subnet mask for a single host (/32)
• 10.1.1.2 → Next-hop IP address (the router/interface to send the packet to)

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🔹 Example: IPv6 Host Route Configuration

To configure a static host route for IPv6:

Command:

Router(config)# ipv6 route 2001:db8:abcd::1/128 2001:db8:1::2

Explanation:

• 2001:db8:abcd::1/128 → Destination IPv6 host
• 2001:db8:1::2 → Next-hop IPv6 address

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🔹 Verifying a Host Route

After configuring, you can verify the host route in the routing table.

For IPv4:

Router# show ip route 192.168.50.10

You’ll see an entry like:

S    192.168.50.10 [1/0] via 10.1.1.2

• S = Static route
• [1/0] = Administrative distance 1, metric 0
• via 10.1.1.2 = Next-hop address

For IPv6:

Router# show ipv6 route 2001:db8:abcd::1

You’ll see something similar:

S   2001:db8:abcd::1/128 [1/0]
     via 2001:db8:1::2

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🔹 Where Host Routes Are Commonly Used in IT Environments

1. Management access
   • To reach a specific router or switch for remote management (like SSH or SNMP).
2. Network control or testing
   • To test connectivity to a single server or endpoint via a particular path.
3. Security or restricted access
   • Allowing communication only to a specific IP (for example, a DNS server or a monitoring tool).
4. Backup or failover
   • Used to direct traffic to a single host when other network routes are down.

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🔹 Key Points for CCNA Exam

Concept	Details
Definition	A route that points to one specific IP address
IPv4 mask	/32 (255.255.255.255)
IPv6 mask	/128
Configuration command	ip route <host-IP> 255.255.255.255 <next-hop> (IPv4) or ipv6 route <host-IP>/128 <next-hop> (IPv6)
Verification command	show ip route / show ipv6 route
Longest Prefix Match rule	Host routes have the highest priority in routing decisions
Common uses	Management, testing, security restrictions, single device connectivity

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✅ Summary

• A Host Route is a route to one single IP address.
• It uses a /32 (IPv4) or /128 (IPv6) prefix.
• It provides most specific routing.
• It can be manually configured with the ip route or ipv6 route command.
• It’s useful for specific device access, network management, and security control.
• Always remember: Host routes override broader network routes due to Longest Prefix Match.

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