BGP Dynamic Neighbors are a way to bring up BGP neighbors without specifically defining the neighbors remote IP address. Using the BGP Listen Range command you specify a range of IP addresses typically on your Hub site (maybe in a DMVPN environment) that you trust to become BGP neigbors with you. When a TCP request […]
BGP
The Border Gateway Protocol (BGP) is an exterior gateway protocol designed to exchange routing and reachability information between autonomous systems (AS) on the internet and now more commonly in enterprise networks.
BGP Weight Attribute – Configuration Tutorial
The BGP weight attribute is the first on the list in the BGP best path algorithm Prefer the path with the highest WEIGHT. Note: WEIGHT is a Cisco-specific parameter. It is local to the router on which it is configured. So if you want to influence your BGP routing outbound on a cisco router you […]
Peering with Route Servers
As your network grows bigger and your internet traffic grows, it starts to make sense to peer directly with other networks rather than simply pay an ISP to deliver all that traffic. Peering is one of the areas in life where the Pareto principle, also known as the 80-20 rule applies: 20% of your potential […]
BGP VPNv4 Troubleshooting Commands
When working with MPLs Layer 3 VPN a lot of people get stuck with the verification, simply because they don’t know the bgp vpnv4 troubleshooting commands. This post will step through some of the verification you can use to verify the routes end to end through a simple MPLS Layer 3 vpn topology. The topology […]
BGP Peer in wrong AS
When configuring BGP with a remote peer you might get the error message BGP peer in wrong AS *Apr 18 08:39:15.455: %BGP-3-NOTIFICATION: received from neighbor 10.0.12.2 passive 2/2 (peer in wrong AS) 2 bytes 0002 This means that you have mis-matched AS numbers in your BGP configuration. You can phone up the remote end and […]
BGP Local Preference
So, what is local preference in BGP? The BGP Local Preference attribute or local-pref is used to influence the outbound routing decision of a router running BGP. The local preference has to be set inbound on routes being received to influence the outbound routing behaviour. A higher local preference is preferred and the default is […]
