How to avoid loop for BGP?

Created Feb 15, 2016 10:17:34Latest reply Feb 15, 2016 20:30:54 1224 1 0 0
How to avoid loop for BGP?
  • x
  • convention:

gennady_fedonov     Created Feb 15, 2016 20:30:54 Helpful(0) Helpful(0)

BGP is different from other IGP protocol; BGP contains rich routing attributes, so BGP is able to filter routing through routing attributes, one of the properties for the AS_PATH.
The AS_Path is used to record all ASs that a route passes through from the local end to the destination in the distance-vector (DV) order. Router will check the AS-PATH attribute when it receives new routes, if there have found its own AS number in the AS_PATH attribute, then it means that the self-published route again return to itself, so there have been a routing loop, this route will be discarded , thus avoiding he routing loop produces.
Of course, BGP router will not release the route come from IBGP peer to others IBGP peers, this is also a method to avoid routing loop.
Under normal circumstances BGP discards the route contains its own AS number in the AS_PATH attribute. But in certain circumstances repeating AS number is reasonable, so you can control by the following command:
[HUAWEI] peer {group-name | peer-ipv4-address} allow-as-loop [number]
The number in the range of <1-10>, the default value is 1, that is allowed to receive routing that contains a self’s AS number in AS-PATH attribute.
  • x
  • convention:


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