Solution to the Problem of Dual Outlets on the Campus Network

Topology

The company leases two bandwidths from the operator, ISP1 is 100M, and ISP2 is 50M. By default, users in the campus access the Internet first through the ISP1 link. Please provide a solution.

Solution 1: When the access route is static

When the carrier access is a static route:
When the static route is connected to the campus network, so at the egress of the campus network, you can use the static floating route to select the route. The default priority of the static route is (pre 60) Configure two default routes on R3, the next one points to the interconnection interface address of R1 and R2, and sets the priority of the static route whose next hop points to AR1 (with a bandwidth of 100M) to (<60), so that 100M can be prioritized When the link of ISP1 fails, it will be detected by AR3, and the default route of standby ISP2 (50M) will take over the static route of ISP1, so as to realize the switchover of the network egress. At the same time, BFD can be used to Link detection and improved switching speed.

Solution 2: When access is dynamically routed

When the access is a dynamic route (IGP/BGP):
When accessing the IGP, the route can be selected based on the cost. By modifying the cost value of AR2 > the cost value of AR1, the link AR1 is selected and becomes the primary link. The link guides packet forwarding, and AR2 becomes the backup link of the egress.
When the access route is BGP, the route can be selected through the route attribute of BGP, and the route-policy routing strategy can be used to modify it, so that the link AR1 becomes the primary link to guide packet forwarding, and AR2 becomes the backup link. road.

Solution 3: Configure the basic functions of active and standby interface backup

Use two or more links to connect to the operator on R3, configure two default routes on R3 to point to two operators respectively, and use standby interface gigabitethernet + standby interface on the main interface. Bind the standby interface and the main interface .Realize the backup function of the active and standby interfaces. Under normal circumstances, the data will go through the main link. When the main interface and the direct link where it is located cannot perform business transmission due to failure, the backup interface will be enabled to improve the reliability of business transmission.

Now that the R1 device control board is down, how to enable campus network users to access the Internet through the ISP2 link (without running dynamic routing protocols), please provide at least two solutions.

Solution 1: Floating static route + BFD linkage solution:

Because two default floating static routes are made on AR3, pointing to AR1 and AR2 routers respectively. When accessing AR1 in a normal way, because the priority of going to AR1 is lower than pre 60, AR3 will choose AR1 when selecting a route. Router.
Now that AR1 fails, this route will disappear, and the next one will not be added to the routing table if it is unreachable. At this time, the configured floating static route to AR2 will appear, and external services can still be accessed. In order to increase the reliability of the network, BFD technology is used for linkage with floating routes, which can quickly detect link failures and speed up the time for switching links. At this time, BFD linkage technology needs to be configured on both devices. If the peer end does not support , you can use the BFD single-arm echo to implement link detection, and BFD can implement millisecond-level fast switching capabilities.
Command reference: IP route-static 0.0.0.0 0 AR1 track bfd-session XXX

Solution 2: Floating static route + NQA linkage solution

Because two default floating static routes are made on AR3, pointing to AR1 and AR2 routers respectively. When accessing AR1 in a normal way, because the priority of going to AR1 is lower than pre 60, AR3 will choose AR1 when selecting a route. router.
Now that AR1 fails, this route will disappear, and the next one will not be added to the routing table if it is unreachable. At this time, the configured floating static route to AR2 will appear, and external services can still be accessed. In order to increase the reliability of the network, the nqa technology is used for linkage. When NQA detects that the AR1 device cannot respond by using ICMP, a route switch must be performed at this time to restore network connectivity as soon as possible. NQA provides second-level convergence speed, and the switchover time is shorter than BFD is long, but the peer device does not need to support NQA technology.
Command reference: IP route-static 0.0.0.0 0 AR1 track NQA XXX