Consider the following use-case: Topology (where the "NOTEBOOK" host is located a the far-right) MOP:

Using "floating" static routes with IP SLA: in the following example, there are two routes (one to a specific ISP router, for instance), one with a default AD (1 for static) that is tracked by an IP SLA reachability operation, and also a second route with an AD of 254 that is not inserted into … Continue reading 10.15 Using IP SLA for Path Control →

Note: IP SLA configuration syntax may vary dependent upon platform or software version. Define the IP SLA probe: The following example shows two actions, including the configuration of an ICMP probe destined to ping 10.1.1.1 every ten seconds from source interface Eth0/0, and a mandatory scheduling of that named SLA operation to begin immediately and … Continue reading 10.14 Configuring IP SLA →

Configuration of IP SLA requires three main steps: Define one or more probes (the monitoring test)Define one or more tracking objects (the subject of the test)Define the action for each tracking object (link the SLA to a policy or route) IP SLAs generate traffic in a continuous and reliable manner based upon the parameters specified … Continue reading 10.13 Cisco IOS IP SLA →

PBR is considered a static method of dynamic path control. Its limitation is that it cannot respond to changes in the network. The dynamic method of path control is IP SLA. It can be used in conjunction with PBR, assessing both the connectivity and performance of a route and dynamically failing to another path if … Continue reading 10.12 Need for Dynamic Path Control →

There are two statements used to configure policy-based routing within the route-map. Match: use an ACL or prefix-list to classify the IP Tuple to match onSet: Define the policy action to take upon the matched traffic The route-map can be applied in one of two ways: To an incoming interface (for traffic passing through the … Continue reading 10.10 Configuring PBR →

PBR has the following benefits and characteristics: Allows for source-based path selection (instead of destination-based paths selection seen in normal IP routing scenarios)... this source-based path selection allows for load-sharing along multiple paths based upon the policy (route-map) configuration.

Here are some notes about PBR: Overrides IP routing, which is destination-based.Applied to incoming, or locally-generated packetsRequires a route map to (a) match specific traffic, and (b) set routing policy Simply put, PBR is used to bypass the routing table in a flexible manner.

Networks configured with redundant paths do not inherently guarantee optimal performance when failures occur. The use of multiple routing protocols or redundant links can lead to sub-optimal routing and odd convergence scenarios. Policy-based routing, or PBR, provides a capability to decide what traffic flows are sent across specific links regardless of the underlying routing protocol … Continue reading 10.7 Need for Path Control →

To show router switching capabilities or status, etc: show ip interface <interface> Default state: CEF and fast-switching enabled on an interface: To disable only CEF and leave fast-switching enabled on an interface: no ip route-cache cef To disable both CEF and fast-switching on an interface: no ip route-cache To disable route caching globally (CEF and … Continue reading 10.6 Analyzing Cisco Express Forwarding →