CCNP Enterprise Core (350-401)

BGP can advertise routes learned from multiple sources, such as static routes, EIGRP, OSPF and more. Every network learned from an indirect sourced needs to be advertised via it’s own network statement, though this can seem tedious for many networks router bgp 65200 network 192.168.1.0 mask 255.255.255.0 network 192.168.2.0 mask 255.255.255.0 … Route summarisation is…

Three tables are used in BGP for maintaining network prefixes and path attributes. Adj-RIB-In The Adj-RIB-In contains the Network Layer Reachability Information (NLRIs) in their original form before any inbound routing policies were applied. This table is purged once all route policies have been processed to save memory. Loc-RIB The Loc-RIB contains all the Network…

By entering network statements into the BGP configuration, it only identifies specific network prefixes to be advertised into the BGP table (Loc-RIB) The network statement is under the address family configuration section of the BGP process configuration. A route-map can be used to tailor routes advertised or setting path attributes to neighbours. The BGP process…

To verify the status of a BGP session, the comand show ip bgp summary or show bgp ipv4 unicast summary can show the current status of sessions with neighbours. The fields in this summary command are defined as follows: Neighbor – The IP address of the peer V – BGP Version used by the peer…

To begin, the BGP routing process needs to be initialised on the router with the command router bgp followed by the ASN, for example router bgp 65512 It is essential that a router ID (RID) is configured on the router, either statically or dynamically. The dynamic router ID uses the highest IP address of any…

BGP sessions with neighbours may report one of six states: Idle Connect Active OpenSent OpenConfirm Established Idle Idle is the first stage in the BGP neighbour state. BGP tries to initiate a TCP connection to the BGP peer and also listens for any incoming connections. If an error causes the BGP session to go the…

Type Name Functional Overview 1 OPEN Sets up the BGP adjacency 2 UPDATE Advertises, updates or removes routes 3 NOTIFICATION Indicates an error to a BGP neighbour 4 KEEPALIVE Ensures that the BGP neighbours are still reachable Summary table of BGP Packet Types OPEN This message is used to establish and set up the BGP…

There are two types of BGP Sessions, the configuration is similar expect eBGPs a unique AS in the remote-as suffix Internal BGP (iBGP) Sessions that established within the same AS are classified as internal BGP sessions. The administrative distance assigned upon placement in the routers table is 200. The TTL on packets from iBGP routers…

To communicate with other BGP routers, BGP unlike other routing protocols does not use hello packets or discover neighbours dynamically. BGP was designed to not support neighbours changing frequently, and configuration to bring up sessions between routers to be co-ordinated by their network administrators. To communicate with other routers, BGP uses TCP port 179 to…

BGP was originally intended just for IPv4 support. Multi Protocol BGP, or MP-BGP, was introduced in RFC 2858 with an extension called the address family identifier. The address family identifier allows multiple specific network protocols in BGP to be supported, such as IPv4 and IPv6. Each address family maintains its own database and configuration information…