Shulou(Shulou.com)06/01 Report--

I. introduction to the usage of static routes

The use of static routes

1) static route priority mode for routing, static route with dynamic route for routing.

2) static routes with SLA inspection links.

3) static routes open the internal and external networks.

4) static routes publish routes.

Static routing is simple to see in the existing network, but it is very flexible to use, and can be used in combination with the above ways.

1.1 static route priority routing (dynamic routing combination)

It is common to use static routes in a small network. As the network grows larger and more complex, static routes often need to be routed. Static priority (administrative distance) routing is commonly used.

The network is divided into two lines, one active line and one backup line.

Active line: use OSPF to issue a default route to the core switch (priority Cisco defaults to 110).

Backup line: a default route is configured on the core device to point to the backup line with a priority of 120.

1.1.1 under normal circumstances:

When the telecommunication line is normal, the core switch equipment chooses the default route issued by OSPF, because the priority of OSPF is lower than that of static route (the smaller the priority, the better).

1.1.2 in case of failure:

In the case of telecommunication line failure, the default route of the telecom egress router does not add a table (routing table). In this case, OSPF does not send a default route to the core switch (in the case of OSPF without alway). In this case, the core switch only has a static route pointing to the backup line, and the core switch switches to the backup line.

1.1.3 failure recovery:

After the failure is restored, the default route of the telecom line exit device is added to the table (routing table). At this time, OSPF finds the default route in the routing table, OSPF sends the default route to the core switch, and the core switch receives the default route passed by OSPF is 110 (when Cisco equipment), because the default route priority of OSPF is 110 less than the default route priority of 120, and the core switch chooses the default route telecom line of OSPF.

1.1.4 Summary:

Automatically switch to the Unicom line when the telecommunication line fails, and automatically switch back to the Unicom line when the fault disappears, which can achieve unattended switching.

Is it really possible to switch completely automatically? If you just stay in the pure theoretical stage, you have done a good job, but in reality there are always a lot of unpredictable problems. Imagination is always beautiful, but reality is cruel.

The next article talks about SLA for link detection, which can perfectly solve the problem that the operator network can not be detected.

to be continued

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