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2.2 IPv4 Routing

OSPF LSAs

1. LSA components Sequence number InitialSequenceNumber = 0x80000001 MaxSequenceNumber= 0x7FFFFFFF When MaxSequnceNumber is reached, and a new update must be sent, the LSA is flushed by setting the Age to MaxAge and reflooding it over all adjacencies. Then, a new version of the LSA is sent with sequence number set …

OSPF Areas

Areas are identified by a 32 bit Area ID. This can be represented as a number in decimal or in dotted decimal format. Area 0 (0.0.0.0) is reserved for backbone. The backbone is responsible for summarizing the topologies of each area to every other area => all inter-area traffic must …

OSPF 101

1. Starting the routing process OSPF can be configured inside the routing process or on the interface. Even a combination of those will be a valid option. The interface configuration will override the routing process configuration. 1.1 Inside the routing process Depending on the IOS version, when 2 network definitions …

More EIGRP Features

1. Router ID The router ID is a 32 bit number, usually represented as a dotted decimal (like an IP address). The Router ID is determined when the routing process is started by the following algorithm: Use the configured value Use the highest up/up loopback ip address Use the highest …

EIGRP Metric

you will have to round down to the nearest integer default K valus: (K1,K2,K3,K4,K5) = (1,0,1,0,0) default EIGRP metric: B+D remember it as BuiLDeR 20 The EIGRP metric is 256 times larger than IGRP metric. 1. Metric Components Bandwidth – B inverse lowest bandwidth along the path in kbps, scaled …

EIGRP 101

1. Starting the routing process EIGRP will advertise routes learned by the EIGRP process and all routes that appear directly connected on the interfaces that are matched by the network command. These include static routes that point to an interface and that are matched by a network command. These routes …

RIP 101

1. Starting the routing process In RIP there is no wildcard option when configuring the network command. The NETWORK-ADDR will always be considered a classful address and will match all interfaces that are in the same classful network: The network command enables RIP on the interfaces where an IP address …

How the routing table is built

1. The Routing Process The routing mechanism involves three different processes: the routing protocols that build the routing table, the routing process that looks up the routing table and the forwarding process that inquires the routing process what to do with a packet. Several routing protocols can run on one …

Policy based Routing

1. In Theory Policy Routing is a feature on Cisco routers that offers greater control over paths in a network. Normal routing is done based on the routing table. The router looks up the destination address of a packet and finds out the next hop or the outgoing interface. With …

ODR

1. What is ODR? ODR(On Demand Routing) is a routing protocol that runs on top of CDP and that is best suited for a hub and spoke topology. If the CDP traffic is already active between the routers on a Hub and Spoke network, the use of ODR makes sense …