CCNP Enterprise Core (350-401)

BGP route filtering is a method of selectively identifying and selecting routes that are advertised from BGP neighbours. By filtering routes, traffic flows can be manipulated. A common scenario of route filtering is from ISPs to customers. An ISP will implement route filtering to ensure only the customers prefixes are allowed over the BGP link…

Route maps can filter networks much in the same way as access control lists or prefix lists, and much more. Route maps have additional capabilities such as allowing the modification or addition of network attributes in BGP. To modify or add network attributes in BGP, a route-map must be referenced by the routing protocol. This…

There can be instances where identifying all the networks from a certain provider may be too complicated or numerous, and a regular expression may be more suitable to filter all networks from a certain AS. Regular expression can be used for this. Quick guide to regular expression Modifier Purpose _ Matches a space ^ Indicates…

Prefix lists provide an alternative method to matching networks with a routing protocol. The prefix list can identify a specific IP address, network, or an entire network range. It is flexible enough to allow of selection of multiple network ranges too. Prefix matching in it’s simplest form can be defined with a 192.168.1.0/24, where it…

Internet Transit If an organisation uses BGP to connect with more than one internet service provider for redundancy, it runs the risk of becoming an accidental transit provider. Using BGPs default configuration, any AS that are received through one BGP peer on one provider, may be advertised out of the other link to the other…

With internet connectivity to a premises, the easiest way to provide a degree of internet connectivity redundancy is to install a second circuit to the internet. If a second circuit is installed and BGP is enabled on it, this is known as BGP multi-homing. BGP multi-homing is when there are multiple BGP sessions to learn…

Configuring BGP with IPv6 is very similar to configuring BGP with IPv4. Additions are obviously the IPv6 address family needs to be activated and neighbours specified, ideally with global unicast addressing. Using link-local addressing opens the risk of unintended link-local address through a MAC address change for example.

Multi Protocol BGP, or MP-BGP, allows BGP to carry multiple network layer reachability information, NLRIs, for multiple protocols. These multiple protocols can include IPv4, IPv6, Multiprotocol Label Switching (MPLS) and Layer 3 virtual private networks – L3VPNs. These MP-BGP features are defined in RFC4760. RFC4760 defines the new address family identifier model (AFI), and new…