简单来说,每一个AS发出路由,AS_Path就会记录下当前发送者AS号 如果记录AS号时发现已经记录过了,那就说明出现了环路 AS_Path可在路由表里查看 IBGP Loop Prevention EBGP防环靠AS_Path,那IBGP防环靠什么呢? BGP Route Reflector和BGP Confederation BGP Route Reflector IBGP中有三个角色: 负责反射路由——route ...
BGP uses the AS_PATH attribute for loop detection and avoidance. TheAS_PATH attributeis a list of AS numbers that the update has traversed. BGP router adds it’s own AS number to the AS_PATH sequence (attribute) when it advertise the update to a neighbor in another AS. If a router se...
Each device uses the network command to advertise IP addresses of LoopBack0 into BGP and filter these routes. Figure 10-15 Using an AS_Path filter to filter BGP routes If no AS_Path filter is used, the original BGP routing table of LSW1 is as follows: [LSW1] display bgp routin...
peer allow-as-loop peer as-number peer as-path-filter peer bfd peer bfd block peer bfd enable peer capability-advertise peer connect-interface peer connected-check-ignore peer default-route-advertise peer description (BGP) peer ebgp-max-hop peer enable (BGP) peer fake-as ...
"allow-as-loop" : 1, "advertise-community" : true, "advertise-ext-community" : true, "nexthop-config" : "local", "prefix-sid" : "default", "reflect-client" : true, "export-route-policy" : "policy1", "import-route-policy" : "policy1", ...
"localAs" : "10", "allowAsLoop" : 1, "ebgpMaxHop" : 1, "peerIgnore" : false, "keepAliveTime" : 0, "holdTime" : 0, "md5Encrypt" : false, "md5Key" : "", "keyChainEnable" : false, "keyChainName" : "keyChainName", ...
In most cases you should set the update-source address to the address of the loopback interface in the current context. By doing this, the TCP connection does not go down until there is no route for the loopback address in the peering router. ...
type: string numAllowedLocalASNumbers: description: Maximum number of local AS numbers that are allowed in the AS path for received routes. This removes BGP loop prevention and should only be used if absolutely necesssary. format: int32 type: integer password: description: Optional BGP password...
It was explained earlier in this chapter how BGP uses the AS_PATH as a loop detection and prevention mechanism because the ASN is prepended when advertising to an EBGP neighbor. IBGP peers do not prepend their ASN to the AS_PATH, because the NLRIs would fail the validity check and would ...
Border Gateway Protocol (BGP) is a path vector protocol that contains path information. It enables the routers to share routing information between autonomous systems (AS) so that loop-free routes can be created. ISPs generally use this protocol. ...