Cisco Route Basics

Metric value <metric>:

Purpose: Calculate the unit of cost (cost) consumed to reach the destination route

Note: The measurement value is generally only valid for the dynamic routing protocol. The measurement value of static routes and directly connected routes is set to 0.

Common metric values: hop count, link bandwidth, link latency, link usage, link reliability, and link MTU

Rip metric value: Number of hops. The smaller the number of hops, the smaller the cost of the route.

OSPF: link bandwidth. The larger the link bandwidth, the smaller the cost it routes.

Management Distance <priority>

Role: Route reliability of a Routing Protocol

Note: For example, RIP and OSPF, the measurement values of two different units cannot be compared. To facilitate the comparison, the path overhead of different routing protocols can be measured through management distance to select the optimal path.

Value: The management distance is the integer value ranging from 0 to 255. 0 is the most trustworthy, and means that no traffic passes through this route.

Management Distance:

Direct Connection interface 0

Outbound interface 0

Next Hop address 1

External BGP 20

Internal MongoDB 90

OSPF 110

Rip 120

Equivalent route

When a vro finds multiple paths to a certain network, it selects the optimal path based on the measurement value. If the number is the same, Server Load balancer can be achieved. A maximum of six routes can be selected before IOS 12.3 (2) T, 16 parallel routes supported by IOS 12.3 (2) T

Re-release Routing

For the routing information from different routing protocols to one destination, the router first determines which Protocol to trust based on the management distance;

For vbrs, there are multiple routing protocols. In this case, you need to make full routing:

For example, the Gateway Router in the IDC uses OSPF. In this case, the default static route is used for data from the Internet. In order to publish the static route to the router route entry in OSPF, re-release the route entry.

Classified route: Route Selection update does not contain Subnet Mask

Classless routing: includes a subnet mask. use IP classless to enable classless routing.

Floating static route

IP Route 10.0.0.0 255.0.0.0 172.16.1.2 130 // 130 is the Management Distance, which is the so-called priority.

Router OSPF 10

Network 172.16.1.0 0.0.0.255 area 0

Network 172.17.1.0 0.0.0.255 area 0

Note: 172.16.1.1 and 172.17.1.1 on the vro enable two OSPF interfaces, and 172.16.1.2 is a backup link,

Because the OSPF management distance is 110, which is smaller than the 130 of the static route, OSPF is used to draw the route table. The default route to 10.0.0.0/8 is defined in OSPF, when OSPF link failure is enabled, route tables are automatically drawn using static routes to implement backup routing.

Cisco Route Basics