Bgp Peers And Peer Groups; Configuring Bgp - 3Com Switch 7700 Configuration Manual

150 C 5: IP R
HAPTER OUTING
BGP Peers and Peer
Groups

Configuring BGP

P O
ROTOCOL PERATION
Route Advertisement Policy
In the Switch 7700, BGP uses the following policies when it advertises routes:
If there are multiple routes available, a BGP speaker only selects the optimum
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one.
A BGP speaker only advertises its own route to its peers.
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A BGP speaker advertises the routes obtained from EBGP to all its BGP peers
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(including EBGP and IBGP peers).
A BGP speaker does not advertise the routes obtained from IBGP to its other
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IBGP peers.
Once the connection is set up, a BGP speaker will advertise all its BGP routes to
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its peers.
Router Selection Policy
In the Switch 7700, BGP uses the following policies when it selects routes:
Discard the routes from an unreachable or unknown next hop.
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Select the routes with the highest local preference.
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Select the routes that originate at the router itself.
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Select the routes with the lowest number of AS-paths.
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Select the routes with the lowest origin.
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Select the routes with the lowest MED value.
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Select the routes learned from EBGP.
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Select the routes advertised by the router with the lowest ID.
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A BGP speaker calls other BGP speakers, peers, when they exchange information.
Multiple related peers compose of a peer group.
In the Switch 7700, a BGP peer must belong to a peer group. If you want to
configure a BGP peer, you first need to create a peer group and then add a peer
into that group.
BGP peer group feature can simplify user configuration and improve route
advertisement efficiency. When added into a peer group, a peer inherits all the
configuration of the group.
If the configuration of a peer group changes, the configuration of its member
peers also changes. Some attributes can be configured to a particular member
peer by specifying its IP address. The attributes configured in this way have a
higher priority than those configured for a peer group. Note that all member peers
must use the same update policy as its group, but may use a different ingress
policy.
BGP configuration includes:
Enabling BGP
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Entering Extended Address Family View
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Configuring Basic Features for a BGP Peer
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