Bgp attributes pdf

The AS_PATH attribute is a list of all ASes that a specific route passes through to reach a specified network. When a router is advertising a BGP route, the AS_PATH attribute is first created empty. Each time the route is advertised from one AS to another, the AS_PATH attribute is modified to prepend the ASN of the router that advertised the •Instead, BGP is a policy-based routing protocol that allows an AS to control traffic flow using multiple BGP attributes. •Routers running BGP exchange network attributes including a list of the full path of BGP AS numbers that a router should take to reach a destination network. •BGP allows an organization to fully use all of its BGP Path Selection Algorithm (continued) •Lowest origin code IGP < EGP < incomplete •Lowest Multi-Exit Discriminator (MED) If bgp deterministic-med, order the paths before comparing If bgp always-compare-med, then compare for all paths otherwise MED only considered if paths are from the same AS (default) BGP · P ART 1 Type About BGP eBGP AD iBGP AD Path Vector 20 200 Standard Protocols Transport Authentication RFC 4271 IP TCP/179 MD5 Path Selection Attribute Weight Administrative preference Description 1 Preference Highest Local Preference Communicated between peers within an AS 2 Highest 3 Self-originated Prefer paths originated locally True If there are any BGP configuration changes, you must reset the neighbor connection to allow the new parameters to take effect. clear ip bgp address Note:€The address is the neighbor address. clear ip bgp * This command clears all neighbor connections. By default, BGP sessions begin with the use of BGP version 4 and negotiate downward to earlier Conveys the IP address of the router or BGP speaker generating the aggregate route Optional & transitive attribute Useful for debugging purposes Does not influence best path selection Creating aggregate using "aggregate-address" sets the aggregator attribute: router bgp 100 aggregate-address 100.1.0.0 255.255.. BGP and BGP Path Attributes - Typically BGP is an EGP (exterior gateway protocol) category protocol that widely used to connect different AS routing domain.BGP is simple straightforward protocol but it become complex when networks grows and need expertise in BGP implementation while you working in enterprise network environment.. BGP runs over TCP protocol on port 179 and for this point-to pConveys the IP address of the router or BGP speaker generating the aggregate route pOptional & transitive attribute pUseful for debugging purposes pDoes not influence best path selection pCreating aggregate using "aggregate-address" sets the aggregator attribute: router bgp 100 aggregate-address 100.1.0.0 255.255.. 13 BGP speaker in the path; he rules for attaching new non-transitive optional attributes will depend on the nature of the specific attribute. [6] BGP attributes controlled by local AS administrator or by neighbor AS administrator, as shown in Table 1 some attributes and who control them. Table 1: BGP Attributes BGP Attributes list: These list of path attributes is used by every BGP router along the path to compare different network paths and the select the ones to move to the BGP table to the routing table. One more attribute that is not included in this list, is the weight attribute. The weight is a Cisco proprietary local attribute that is not View bgp attributes.pdf from IS MISC at IIT Kanpur. Deployment and Operation of BGP Denise Fishburne, Oliver Böhmer TECRST-1310 rev0207 Agenda • • • •