Question

A Cisco router has the following routes in its route table:

10.0.0.0/8 known via EIGRP (administrative distance 90)
10.1.0.0/16 known via OSPF (administrative distance 110)
10.1.1.0/24 known via RIPv2 (administrative distance 120)
10.1.1.0/25 known via internal BGP (administrative distance 200)
10.1.1.0/27 known via static (administrative distance 1)
Given these route entries, which route will be used to forward packets to host 10.1.1.254?

O The router will use the static route
O The router will use the IBGP route
O The router will use the RIPv2 route
O The router will use the OSPF route
O The router will use the EIGRP route

Answer 1

The router will use the static route to 10.1.1.0/27 to forward packets to host 10.1.1.254 because it is the most specific route with the lowest administrative distance.

Step-by-step explanation:

To determine which route will be used to forward packets to host 10.1.1.254, we must look at both the prefix length (or subnet mask) and the administrative distance (AD) of each route. The route with the longest matching prefix length (the most specific route) that has the lowest administrative distance will be chosen. Here are the routes organized by prefix length and administrative distance:

• 10.0.0.0/8 via EIGRP (AD 90)
• 10.1.0.0/16 via OSPF (AD 110)
• 10.1.1.0/24 via RIPv2 (AD 120)
• 10.1.1.0/25 via internal BGP (IBGP) (AD 200)
• 10.1.1.0/27 via static (AD 1)

Host 10.1.1.254 falls within the 10.1.1.0/27 subnet. Thus the most specific route is the static route with a prefix length of /27. It also has the lowest administrative distance (1) compared to all the other routes that could potentially match. Therefore, the static route to 10.1.1.0/27 will be used to forward packets to host 10.1.1.254.