Summary Route Calculator Download
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Summary static routes can be used to help minimize the number of static routes in the routing table. Using summary static routes can also make management of a large number of static routes easier and less prone to errors. Floating static routes can be used as a backup route for another static route or a dynamic routing protocol.
A single IPv4 static summary route can be used to replace multiple static routes when those routes can be summarized with a common prefix length. The configuration of a summary static route is similar to the configuration of other IPv4 static routes.
Route summarization, also known as route aggregation, is the process of advertising a contiguous set of addresses as a single address with a less-specific, shorter subnet mask. CIDR is a form of route summarization and is synonymous with the term supernetting.
In this activity, you will calculate and configure summary routes. Route summarization, also known as route aggregation, is the process of advertising a contiguous set of addresses as a single address.
In this activity, you will calculate and configure summary routes. Route summarization, also known as route aggregation, is the process of advertising a contiguous set of addresses as a single address. After calculating summary routes for each LAN, you must summarize a route which includes all networks in the topology in order for the ISP to reach each LAN.
Similar to IPv4, a single IPv6 static summary route can be used to replace multiple IPv6 static routes with a common prefix length. The calculation and configuration of an IPv6 summary static route is similar to the configuration of an IPv4 static summary route.
In this activity, you will calculate, configure, and verify a summary route for all the networks R1 can access through R2. R1 is configured with a loopback interface. Instead of adding a LAN or another network to R1, we can use a loopback interface to simplify testing when verifying routing.
There may be times when a primary route fails due to physical layer problems, hardware issues, a misconfiguration, or many other reasons. A floating static route can be used as a backup route when there is a secondary path available.
Floating static routes are static routes that have an administrative distance greater than the administrative distance of another static route or dynamic routes. They are very useful when providing a backup to a primary link, as shown in Figure 2-66.
By default, static routes have an administrative distance of 1, making them preferable to routes learned from dynamic routing protocols. For example, the administrative distances of some common dynamic routing protocols are:
A floating static route can be used to provide a backup route to multiple interfaces or networks on a router. It is also encapsulation independent, meaning it can be used to forward packets out any interface, regardless of encapsulation type.
An important consideration of a floating static route is that it is affected by convergence time. A route that is continuously dropping and re-establishing a connection can cause the backup interface to be activated unnecessarily.
IPv4 static routes are configured using the ip route global configuration command and specifying an administrative distance. If no administrative distance is configured, the default value (1) is used.
R1 is configured with a default static route pointing to R2. Because no administrative distance is configured, the default value (1) is used for this static route. R1 is also configured with a floating static default pointing to R3 with an administrative distance of 5. This value is greater than the default value of 1 and, therefore, this route floats and is not present in the routing table, unless the preferred route fails.
Because the default static route on R1 to R2 has an administrative distance of 1, traffic from R1 to R3 should go through R2. The output in Figure 2-68 confirms that traffic between R1 and R3 flows through R2.
Notice in the following output that R1 automatically generates messages indicating that the serial interface to R2 is down. A look at the routing table verifies that the default route is now pointing to R3 using the floating static default route configured for next-hop 10.10.10.2.
In this activity, you will configure a floating static route. A floating static route is used as a backup route. It has a manually configured administrative distance greater than that of the primary route and therefore would not be in the routing table until the primary route fails. You will test failover to the backup route, and then restore connectivity to the primary route.
Networks or subnets combined into single nework with common CIDR mask is called supernets or supernetworks. The common routing prefix of supernet is aggregated from the prefixes of given networks or subnets and it must be smaller or the same as smallest component network prefix. This concept of creating a supernet is called supernetting or routing aggregation. Route aggregation reduces the number of advertised routes on huge networks by summarizing routes.
Supernetting was introduced to solve the problem with rapidly growing routing tables and because of IP version 4 address pool exhaustion. The main benefits of route aggregation (supernetting) are less memory and CPU power requirments for storing and processing routes. More information about supernets can be found in RFC 1338 - Supernetting: an address assignment and aggregation strategy.
When we calculate this from binary back to hexadecimal we get AB80. The first three hextets are the same and in the 4th octet we have 9 bits that are the same. 48 + 9 = 57 bits. Our summary address will be:
When we calculate this from binary back to hexadecimal we get 0000. The first three hextets are the same and in the 4th octet we have 14 bits that are the same. 48 + 14 = 62 bits. Our summary address will be:
Step 2. Count the number of far-left matching bits to determine the mask for the summary route. Figure 2 highlights the 14 far left matching bits. This is the prefix, or subnet mask, for the summarized route: /14 or 255.252.0.0.
A static summary route is used to minimize the number of static routes in the routing table and lessen the administrative overhead that may impact the memory usage of the routers. Using a static summary route efficiently manages a large number of static routes in the routing table, which lessens the probability of errors occurring.
Multiple static routes can be replaced by a single static summary route, given that those routes have a common prefix length. Configuring a static summary route is just the same as how we configure a static route.
The process of advertising multiple sets of addresses as a single address with a less specific and shorter subnet mask is how we simply define Route Summarization. Classless InterDomain Routing (CIDR) is synonymous with Supernetting and is a form of route summarization. CIDR overlooks the limitation of classful boundaries and allows summarization with subnet masks that are smaller than the default classful subnet masks.
The following output below shows the static routing table entries for R3. The following output displays the routing information, the routing table static route entries, of R3. Notice that it has three static routes in contiguous ranges that can be summarized because the destination network shares the same two first octets, 192.168.
Upon investigation it turns out that quite a big part of routing process depends on adding L.Routing.control to map. To force route calculation and prevent showing of route on the map requires some hacking trickery:
The traditional approach to calculate signal length is to add up the centerline length of all segments used in a route, as well as the vertical distance due to the height of the vias, which was originally determined by the board thickness.
Each router has its own view of the topology even though all the routers build a shortest path tree which uses the same link-state database. These sections indicate what is involved in the creation of a shortest path tree.
After the router builds the shortest path tree, it builds the routing table. Directly connected networks are reached via a metric (cost) of 0 and other networks are reached in accord with the cost calculated in the tree.
Routers that act as gateways (redistribution) between OSPF and other routing protocols (IGRP, EIGRP, IS-IS, RIP, BGP, Static) or other instances of the OSPF routing process are called autonomous system boundary router (ASBR). Any router can be an ABR or an ASBR.
By default, a router uses a Null authentication which means that routing exchanges over a network are not authenticated. Two other authentication methods exist: Simple password authentication and Message Digest authentication (MD-5).
Virtual links are discussed in the next section. Note the different types of routing information. Routes that are generated from within an area (the destination belongs to the area) are called intra-area routes.
These routes are normally represented by the letter O in the IP routing table. Routes that originate from other areas are called inter-area or Summary routes.
The notation for these routes is O IA in the IP routing table. Routes that originate from other routing protocols (or different OSPF processes) and that are injected into OSPF via redistribution are called external routes.
These routes are represented by O E2 or O E1 in the IP routing table. Multiple routes to the same destination are preferred in this order: intra-area, inter-area, external E1, external E2. External types E1 and E2 are explained later.
In this way RTA and area 1 has a logical connection to the backbone. In order to configure a virtual link, use the area virtual-link router OSPF sub-command on both RTA and RTB, where area-id is the transit area.
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