DMVPN, GRE, and NHRP

DMVPN is a design concept. The idea is to create tunnels between devices (HUB- SPOKE or SPOKE-to-SPOKE) to pass traffic between them. DMVPN emulates a cloud where we can combine different types of traffic (Multicast, broadcast) and send it as a unicast through the tunnel. GRE (Generic Routing Encapsulation) is the TCP/IP protocol used to

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The Simplest Way to Configure BGP “Weight” Attribute Path.

BGP uses an algorithm called (“BGP Best Path Selection”) to identify the best path and place it in the routing table of a router so traffic will be forwarded using that path. Depending of the situation,  we can influence how BGP chooses a path to a particular destination by using path attributes. The very first

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Policy-Based Routing (PBR)

Policy Base Routing is a way to bypass the regular mechanism that a router has to route packets. Basically, when a router receives a packet at the incoming interface, it “deencapsulates”  the Data Link Layer header and then processes the layer 3 information by looking the destination IP address of the packet in its routing

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Beating BGP TCP Connection Failure with Loopbacks

In order for BGP to form a neighbor relationship, it needs to establish a TCP session between its peers. (The Famous “TCP Hand- Shake.”) BGP uses the IP address  configured in the “Outgoing Interface” that the router will use to establish the neighbor relationship in the “neighbor” command to reach its peer as the “source

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iBGP Neighbor Reachability Issues

BGP is an external routing protocol that advertises routes between and within autonomous systems. When BGP advertises external routes (eBGP), it uses its own mechanism to avoid loops. This is accomplished by a BGP attribute called “AS_PATH.” The autonomous system path attribute is triggered by BGP when there is not PAs (Path Attributes) set under

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Redistribution with Route Maps

Using a route-map as referenced on the “redistribute” command provides many features. For example, we can tweak routes while filtering them at the same time, edit metrics, or assign external route types among others.   Route maps are similar to “programming  logic.” For example, when programmers create statements in their code, they might use (

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MPLS (Multiprotocol Label Switching) Transport

MPLS (Multiprotocol Label Switching) Transport   MPLS is a service provider technology where they can squeeze MPLS labels just right before the layer 2 header, so SP can route almost any type of traffic from a specific source to a specific destination using labels. There is two main benefits MPLS provides: 1 –> Improve Routing

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Route Reflector

Route Reflector is mechanism to avoid routing loops. Basically, when a route is learned via iBPG, it will not be advertised to another iBPG router within the same “Autonomous System.” It is the BPG split horizon rule. Therefore, routes learned via iBGP are never propagated to other iBGP peers.   There are three types of

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eBGP Multihop when Configuring eBGP Peers with Loopback Interfaces

Most of time we might prefer to configure loopback interfaces to establish BGP neighbors because, as long as the router stays up, loopback interfaces will stay up as well. However, we need to tweak the BGP configuration. For example we need to update the source of the neighbor with the interface (loopback) we want to

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BGP Peer-groups

BGP peer group is a set of BGP neighbors that shares the same outbound policy, whereas the inbound policy might be different.  When BGP is configured on routers, it processes updates on a neighbor-by-neighbor basis. This requires CPU resources to be pulled  from the router  for each neighbor update that is processed. However, when we

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