3Com 3C13636 Configuration Manual page 689

3Com Router 3000 Ethernet Family
Configuration Guide
Cancel the filtering of the routes to be
advertised by BGP
By default, BGP does not filter received and advertised routing information.
To have BGP filter the routes redistributed from a particular routing protocol, specify the
protocol argument, which can take the value of direct, static, RIP, IS-IS, OSPF,
OSPF-ASE or OSPF-NSSA.
For more information, refer to the "Configure Route Filtering" part in "IP Routing Policy
Configuration".
6.2.20 Configuring BGP Load Balancing
The load balancing implementations of BGP and IGP are different:
IGP calculates metrics for different routes to the same destination address
according to its route algorithm and perform load balancing between routes with
identical metrics.
BGP cannot determine whether to perform load balancing based on an explicit
metric since it has no route algorithm. However, it can select routes to implement
load balancing depending on its abundant routing rules, that is, it adds load
balancing into its routing rules.
V 2.41 supports BGP load balancing. When BGP load balancing is configured, upon
BGP route selection, a rule is added between the last two routing rules "Select routes
learned from EBGP first" and "Select routes advertised by the routers with lowest BGP
ID first". That is, if load balancing is configured and there are multiple external routes
heading for the same AS or AS confederation, BGP will select multiple routes for load
balancing.
The implementation of BGP load balancing follows these rules:
The participating routes must be those redistributed from EBGP.
These routes must come from the same AS and have the same metric value.
These routes must have the same AS_PATH property and origin property (IGP,
EGP, or INC).
Operation
3Com Corporation
6-24
Chapter 6 BGP Configuration
Command
undo filter-policy
ip-prefix ip-prefix-name
[protocol ]
acl-number |
} export