Cisco Router Challenge 82
Outline
This challenge involves the configuration of BGP for the atomic aggregation
attribute.The objectives of this challenge are to:
- Define BGP.
- Defines neighbors.
- Define aggregate-address.
Commands
# config
t
(config)#
router bgp 172
(config-router)# neighbor 11.11.11.11
remote-as 300
(config-router)# neighbor 12.12.12.12
remote-as 311
(config-router)# network 160.0.0.0
(config-router)# aggregate-address 160.0.0.0 255.0.0.0
Example
# config
t
(config)#
router bgp 172
Router(config-router)# ?
Router configuration commands:
address-family Enter Address Family command mode
aggregate-address Configure BGP aggregate entries
auto-summary Enable automatic network number
summarization
bgp BGP
specific commands
default Set a command to its defaults
default-information Control distribution of default
information
default-metric Set metric of redistributed routes
distance Define an administrative distance
distribute-list Filter networks in routing updates
exit Exit
from routing protocol configuration mode
help Description of the interactive
help system
maximum-paths Forward packets over multiple paths
neighbor Specify a neighbor
router
network Specify a network to announce via
BGP
no Negate a command or set its
defaults
redistribute Redistribute
information from another routing protocol
synchronization Perform IGP synchronization
table-map Map external entry attributes into
routing table
timers Adjust routing timers
(config-router) # nei
11.11.11.11 ?
activate Enable the Address Family for
this Neighbor
advertise-map specify route-map for conditional
advertisement
advertisement-interval Minimum interval between sending BGP
routing updates
allowas-in
Accept as-path with my AS present in it
default-originate Originate default route to this neighbor
description Neighbor
specific description
distribute-list Filter updates to/from this neighbor
ebgp-multihop Allow EBGP neighbors
not on directly connected
networks
filter-list Establish BGP filters
local-as Specify a local-as number
maximum-prefix Maximum number of prefix accept from
this peer
next-hop-self Disable the next hop calculation for
this neighbor
next-hop-unchanged Propagate the iBGP
paths's next hop unchanged for
this
neighbor
password Set a password
peer-group Member of the peer-group
prefix-list Filter updates to/from this neighbor
remote-as Specify a BGP neighbor
remove-private-AS Remove private AS number from outbound
updates
route-map Apply route map to neighbor
route-reflector-client Configure a neighbor
as Route Reflector client
send-community Send Community attribute to this neighbor
shutdown Administratively shut down this
neighbor
soft-reconfiguration Per neighbor soft
reconfiguration
timers BGP per neighbor
timers
translate-update Translate Update to MBGP format
unsuppress-map
Route-map to selectively unsuppress suppressed
routes
update-source Source of routing updates
version Set the BGP version to match a
neighbor
weight Set default weight for routes
from this neighbor
(config-router)# neighbor 11.11.11.11
remote-as 300
(config-router)# neighbor 12.12.12.12
remote-as 311
(config-router)# network 160.0.0.0
(config-router)# aggregate-address ?
A.B.C.D Aggregate address
(config-router)# aggregate-address 160.0.0.0 255.0.0.0
Explanation
With the atomic aggregation attribute, multiple destinations are grouped
within a single update. Thus:
(config-router)#
aggregate-address 160.0.0.0 255.0.0.0
means that there are many routes contained, and have been aggregated into a
single route. This will then create a single routing entry in the BGP routing
table.
Topology
The basic topology is defined below, where AS1 is connected to E0, AS2 to
S0, and AS3 to S1.
