Dell S4048-ON, Configuration Manual

Page: 207 / 1039

The
show ip bgp network
command includes multipath information for that network.
• Enable multiple parallel paths.
CONFIG-ROUTER-BGP mode
maximum-paths {ebgp | ibgp} number
Filtering BGP Routes
Filtering routes allows you to implement BGP policies.
You can use either IP prefix lists, route maps, AS-PATH ACLs or IP community lists (using a route map) to control which routes the
BGP neighbor or peer group accepts and advertises. Prefix lists filter routes based on route and prefix length, while AS-Path ACLs
filter routes based on the ASN. Route maps can filter and set conditions, change attributes, and assign update policies.
NOTE: Dell Networking OS supports up to 255 characters in a set community statement inside a route map.
NOTE: You can create inbound and outbound policies. Each of the commands used for filtering has
in
and
out
parameters that you must apply. In Dell Networking OS, the order of preference varies depending on whether the
attributes are applied for inbound updates or outbound updates.
For inbound and outbound updates the order of preference is:
• prefix lists (using the
neighbor distribute-list
command)
• AS-PATH ACLs (using the
neighbor filter-list
command)
• route maps (using the
neighbor route-map
command)
Prior to filtering BGP routes, create the prefix list, AS-PATH ACL, or route map.
For configuration information about prefix lists, AS-PATH ACLs, and route maps, refer to Access Control Lists (ACLs) .
NOTE: When you configure a new set of BGP policies, to ensure the changes are made, always reset the neighbor or
peer group by using the
clear ip bgp
command in EXEC Privilege mode.
To filter routes using prefix lists, use the following commands.
1. Create a prefix list and assign it a name.
CONFIGURATION mode
ip prefix-list prefix-name
2. Create multiple prefix list filters with a deny or permit action.
CONFIG-PREFIX LIST mode
seq sequence-number {deny | permit} { any | ip-prefix [ge | le] }
•
ge
: minimum prefix length to be matched.
•
le
: maximum prefix length to me matched.
For information about configuring prefix lists, refer to Access Control Lists (ACLs) .
3. Return to CONFIGURATION mode.
CONFIG-PREFIX LIST mode
exit
4. Enter ROUTER BGP mode.
CONFIGURATION mode
router bgp as-number
5. Filter routes based on the criteria in the configured prefix list.
CONFIG-ROUTER-BGP mode
Border Gateway Protocol IPv4 (BGPv4)
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